/*=============================================================================|
|  PROJECT Sharp7                                                        1.0.0 |
|==============================================================================|
|  Copyright (C) 2016 Davide Nardella                                          |
|  All rights reserved.                                                        |
|==============================================================================|
|  Sharp7 is free software: you can redistribute it and/or modify              |
|  it under the terms of the Lesser GNU General Public License as published by |
|  the Free Software Foundation, either version 3 of the License, or           |
|  (at your option) any later version.                                         |
|                                                                              |
|  It means that you can distribute your commercial software which includes    |
|  Sharp7 without the requirement to distribute the source code of your        |
|  application and without the requirement that your application be itself     |
|  distributed under LGPL.                                                     |
|                                                                              |
|  Sharp7 is distributed in the hope that it will be useful,                   |
|  but WITHOUT ANY WARRANTY; without even the implied warranty of              |
|  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the               |
|  Lesser GNU General Public License for more details.                         |
|                                                                              |
|  You should have received a copy of the GNU General Public License and a     |
|  copy of Lesser GNU General Public License along with Sharp7.                |
|  If not, see  http://www.gnu.org/licenses/                                   |
|=============================================================================*/
using System;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;
//------------------------------------------------------------------------------
// If you are compiling for UWP verify that WINDOWS_UWP or NETFX_CORE are 
// defined into Project Properties->Build->Conditional compilation symbols
//------------------------------------------------------------------------------
#if WINDOWS_UWP || NETFX_CORE
using System.Threading.Tasks;
using Windows.Networking;
using Windows.Networking.Sockets;
using Windows.Storage.Streams;
#else // <-- Including MONO
using System.Net.Sockets;

#endif

namespace Sharp7
{
	#region [Async Sockets UWP(W10,IoT,Phone)/Windows 8/Windows 8 Phone]
#if WINDOWS_UWP || NETFX_CORE
    class MsgSocket
    {
        private DataReader Reader = null;
        private DataWriter Writer = null;
        private StreamSocket TCPSocket;

        private bool _Connected;

        private int _ReadTimeout = 2000;
        private int _WriteTimeout = 2000;
        private int _ConnectTimeout = 1000;

        public static int LastError = 0;


        private void CreateSocket()
        {
            TCPSocket = new StreamSocket();
            TCPSocket.Control.NoDelay = true;
            _Connected = false;
        }

        public MsgSocket()
        {
        }

        public void Close()
        {
            if (Reader != null)
            {
                Reader.Dispose();
                Reader = null;
            }
            if (Writer != null)
            {
                Writer.Dispose();
                Writer = null;
            }
            if (TCPSocket != null)
            {
                TCPSocket.Dispose();
                TCPSocket = null;
            }
            _Connected = false;
        }

        private async Task AsConnect(string Host, string port, CancellationTokenSource cts)
        {
            HostName ServerHost = new HostName(Host);
            try
            {
                await TCPSocket.ConnectAsync(ServerHost, port).AsTask(cts.Token);
                _Connected = true;
            }
            catch (TaskCanceledException)
            {
                LastError = S7Consts.errTCPConnectionTimeout;
            }
            catch
            {
                LastError = S7Consts.errTCPConnectionFailed; // Maybe unreachable peer
            }
        }

        public int Connect(string Host, int Port)
        {
            LastError = 0;
            if (!Connected)
            {
                CreateSocket();
                CancellationTokenSource cts = new CancellationTokenSource();
                try
                {
                    try
                    {
                        cts.CancelAfter(_ConnectTimeout);
                        Task.WaitAny(Task.Run(async () => await AsConnect(Host, Port.ToString(), cts)));
                    }
                    catch
                    {
                        LastError = S7Consts.errTCPConnectionFailed;
                    }
                }
                finally
                {
                    if (cts != null)
                    {
                        try
                        {
                            cts.Cancel();
                            cts.Dispose();
                            cts = null;
                        }
                        catch { }
                    }

                }
                if (LastError == 0)
                {
                    Reader = new DataReader(TCPSocket.InputStream);
                    Reader.InputStreamOptions = InputStreamOptions.Partial;
                    Writer = new DataWriter(TCPSocket.OutputStream);
                    _Connected = true;
                }
                else
                    Close();
            }
            return LastError;
        }

        private async Task AsReadBuffer(byte[] Buffer, int Size, CancellationTokenSource cts)
        {
            try
            {
                await Reader.LoadAsync((uint)Size).AsTask(cts.Token);
                Reader.ReadBytes(Buffer);
            }
            catch
            {
                LastError = S7Consts.errTCPDataReceive;
            }
        }

        public int Receive(byte[] Buffer, int Start, int Size)
        {
            byte[] InBuffer = new byte[Size];
            CancellationTokenSource cts = new CancellationTokenSource();
            LastError = 0;
            try
            {
                try
                {
                    cts.CancelAfter(_ReadTimeout);
                    Task.WaitAny(Task.Run(async () => await AsReadBuffer(InBuffer, Size, cts)));
                }
                catch
                {
                    LastError = S7Consts.errTCPDataReceive;
                }
            }
            finally
            {
                if (cts != null)
                {
                    try
                    {
                        cts.Cancel();
                        cts.Dispose();
                        cts = null;
                    }
                    catch { }
                }
            }
            if (LastError == 0)
                Array.Copy(InBuffer, 0, Buffer, Start, Size);
            else
                Close();
            return LastError;
        }

        private async Task WriteBuffer(byte[] Buffer, CancellationTokenSource cts)
        {
            try
            {
                Writer.WriteBytes(Buffer);
                await Writer.StoreAsync().AsTask(cts.Token);
            }
            catch
            {
                LastError = S7Consts.errTCPDataSend;
            }
        }

        public int Send(byte[] Buffer, int Size)
        {
            byte[] OutBuffer = new byte[Size];
            CancellationTokenSource cts = new CancellationTokenSource();
            Array.Copy(Buffer, 0, OutBuffer, 0, Size);
            LastError = 0;
            try
            {
                try
                {
                    cts.CancelAfter(_WriteTimeout);
                    Task.WaitAny(Task.Run(async () => await WriteBuffer(OutBuffer, cts)));
                }
                catch
                {
                    LastError = S7Consts.errTCPDataSend;
                }
            }
            finally
            {
                if (cts != null)
                {
                    try
                    {
                        cts.Cancel();
                        cts.Dispose();
                        cts = null;
                    }
                    catch { }
                }
            }
            if (LastError != 0)
                Close();
            return LastError;
        }

        ~MsgSocket()
        {
            Close();
        }

        public bool Connected
        {
            get
            {
                return (TCPSocket != null) && _Connected;
            }
        }

        public int ReadTimeout
        {
            get
            {
                return _ReadTimeout;
            }
            set
            {
                _ReadTimeout = value;
            }
        }

        public int WriteTimeout
        {
            get
            {
                return _WriteTimeout;
            }
            set
            {
                _WriteTimeout = value;
            }
        }
        public int ConnectTimeout
        {
            get
            {
                return _ConnectTimeout;
            }
            set
            {
                _ConnectTimeout = value;
            }
        }
    }
#endif
	#endregion

	#region [Sync Sockets Win32/Win64 Desktop Application]
#if !WINDOWS_UWP && !NETFX_CORE
	internal class MsgSocket
	{
		private Socket TCPSocket;
		private int _ReadTimeout = 2000;
		private int _WriteTimeout = 2000;
		private int _ConnectTimeout = 1000;
		public int LastError = 0;

		public MsgSocket()
		{
		}

		~MsgSocket()
		{
			Close();
		}

		public void Close()
		{
			if (TCPSocket != null)
			{
				TCPSocket.Dispose();
				TCPSocket = null;
			}
		}

		private void CreateSocket()
		{
			TCPSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
			TCPSocket.NoDelay = true;
		}

		private void TCPPing(string Host, int Port)
		{
			// To Ping the PLC an Asynchronous socket is used rather then an ICMP packet.
			// This allows the use also across Internet and Firewalls (obviously the port must be opened)           
			LastError = 0;
			Socket PingSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
			try
			{
				IAsyncResult result = PingSocket.BeginConnect(Host, Port, null, null);
				bool success = result.AsyncWaitHandle.WaitOne(_ConnectTimeout, true);
				if (!success)
				{
					LastError = S7Consts.errTCPConnectionFailed;
				}
			}
			catch
			{
				LastError = S7Consts.errTCPConnectionFailed;
			};
			PingSocket.Close();
		}

		public int Connect(string Host, int Port)
		{
			LastError = 0;
			if (!Connected)
			{
				TCPPing(Host, Port);
				if (LastError == 0)
					try
					{
						CreateSocket();
						TCPSocket.Connect(Host, Port);
					}
					catch
					{
						LastError = S7Consts.errTCPConnectionFailed;
					}
			}
			return LastError;
		}

		private int WaitForData(int Size, int Timeout)
		{
			bool Expired = false;
			int SizeAvail;
			int Elapsed = Environment.TickCount;
			LastError = 0;
			try
			{
				SizeAvail = TCPSocket.Available;
				while ((SizeAvail < Size) && (!Expired))
				{
					Thread.Sleep(2);
					SizeAvail = TCPSocket.Available;
					Expired = Environment.TickCount - Elapsed > Timeout;
					// If timeout we clean the buffer
					if (Expired && (SizeAvail > 0))
						try
						{
							byte[] Flush = new byte[SizeAvail];
							TCPSocket.Receive(Flush, 0, SizeAvail, SocketFlags.None);
						}
						catch { }
				}
			}
			catch
			{
				LastError = S7Consts.errTCPDataReceive;
			}
			if (Expired)
			{
				LastError = S7Consts.errTCPDataReceive;
			}
			return LastError;
		}

		public int Receive(byte[] Buffer, int Start, int Size)
		{

			int BytesRead = 0;
			LastError = WaitForData(Size, _ReadTimeout);
			if (LastError == 0)
			{
				try
				{
					BytesRead = TCPSocket.Receive(Buffer, Start, Size, SocketFlags.None);
				}
				catch
				{
					LastError = S7Consts.errTCPDataReceive;
				}
				if (BytesRead == 0) // Connection Reset by the peer
				{
					LastError = S7Consts.errTCPDataReceive;
					Close();
				}
			}
			return LastError;
		}

		public int Send(byte[] Buffer, int Size)
		{
			LastError = 0;
			try
			{
				int BytesSent = TCPSocket.Send(Buffer, Size, SocketFlags.None);
			}
			catch
			{
				LastError = S7Consts.errTCPDataSend;
				Close();
			}
			return LastError;
		}

		public bool Connected
		{
			get
			{
				return (TCPSocket != null) && (TCPSocket.Connected);
			}
		}

		public int ReadTimeout
		{
			get
			{
				return _ReadTimeout;
			}
			set
			{
				_ReadTimeout = value;
			}
		}

		public int WriteTimeout
		{
			get
			{
				return _WriteTimeout;
			}
			set
			{
				_WriteTimeout = value;
			}

		}
		public int ConnectTimeout
		{
			get
			{
				return _ConnectTimeout;
			}
			set
			{
				_ConnectTimeout = value;
			}
		}
	}
#endif
	#endregion

	public static class S7Consts
	{
		#region [Exported Consts]
		// Error codes
		//------------------------------------------------------------------------------
		//                                     ERRORS                 
		//------------------------------------------------------------------------------
		public const int errTCPSocketCreation = 0x00000001;
		public const int errTCPConnectionTimeout = 0x00000002;
		public const int errTCPConnectionFailed = 0x00000003;
		public const int errTCPReceiveTimeout = 0x00000004;
		public const int errTCPDataReceive = 0x00000005;
		public const int errTCPSendTimeout = 0x00000006;
		public const int errTCPDataSend = 0x00000007;
		public const int errTCPConnectionReset = 0x00000008;
		public const int errTCPNotConnected = 0x00000009;
		public const int errTCPUnreachableHost = 0x00002751;

		public const int errIsoConnect = 0x00010000; // Connection error
		public const int errIsoInvalidPDU = 0x00030000; // Bad format
		public const int errIsoInvalidDataSize = 0x00040000; // Bad Datasize passed to send/recv : buffer is invalid

		public const int errCliNegotiatingPDU = 0x00100000;
		public const int errCliInvalidParams = 0x00200000;
		public const int errCliJobPending = 0x00300000;
		public const int errCliTooManyItems = 0x00400000;
		public const int errCliInvalidWordLen = 0x00500000;
		public const int errCliPartialDataWritten = 0x00600000;
		public const int errCliSizeOverPDU = 0x00700000;
		public const int errCliInvalidPlcAnswer = 0x00800000;
		public const int errCliAddressOutOfRange = 0x00900000;
		public const int errCliInvalidTransportSize = 0x00A00000;
		public const int errCliWriteDataSizeMismatch = 0x00B00000;
		public const int errCliItemNotAvailable = 0x00C00000;
		public const int errCliInvalidValue = 0x00D00000;
		public const int errCliCannotStartPLC = 0x00E00000;
		public const int errCliAlreadyRun = 0x00F00000;
		public const int errCliCannotStopPLC = 0x01000000;
		public const int errCliCannotCopyRamToRom = 0x01100000;
		public const int errCliCannotCompress = 0x01200000;
		public const int errCliAlreadyStop = 0x01300000;
		public const int errCliFunNotAvailable = 0x01400000;
		public const int errCliUploadSequenceFailed = 0x01500000;
		public const int errCliInvalidDataSizeRecvd = 0x01600000;
		public const int errCliInvalidBlockType = 0x01700000;
		public const int errCliInvalidBlockNumber = 0x01800000;
		public const int errCliInvalidBlockSize = 0x01900000;
		public const int errCliNeedPassword = 0x01D00000;
		public const int errCliInvalidPassword = 0x01E00000;
		public const int errCliNoPasswordToSetOrClear = 0x01F00000;
		public const int errCliJobTimeout = 0x02000000;
		public const int errCliPartialDataRead = 0x02100000;
		public const int errCliBufferTooSmall = 0x02200000;
		public const int errCliFunctionRefused = 0x02300000;
		public const int errCliDestroying = 0x02400000;
		public const int errCliInvalidParamNumber = 0x02500000;
		public const int errCliCannotChangeParam = 0x02600000;
		public const int errCliFunctionNotImplemented = 0x02700000;
		//------------------------------------------------------------------------------
		//        PARAMS LIST FOR COMPATIBILITY WITH Snap7.net.cs           
		//------------------------------------------------------------------------------
		public const Int32 p_u16_LocalPort = 1;  // Not applicable here
		public const Int32 p_u16_RemotePort = 2;
		public const Int32 p_i32_PingTimeout = 3;
		public const Int32 p_i32_SendTimeout = 4;
		public const Int32 p_i32_RecvTimeout = 5;
		public const Int32 p_i32_WorkInterval = 6;  // Not applicable here
		public const Int32 p_u16_SrcRef = 7;  // Not applicable here
		public const Int32 p_u16_DstRef = 8;  // Not applicable here
		public const Int32 p_u16_SrcTSap = 9;  // Not applicable here
		public const Int32 p_i32_PDURequest = 10;
		public const Int32 p_i32_MaxClients = 11; // Not applicable here
		public const Int32 p_i32_BSendTimeout = 12; // Not applicable here
		public const Int32 p_i32_BRecvTimeout = 13; // Not applicable here
		public const Int32 p_u32_RecoveryTime = 14; // Not applicable here
		public const Int32 p_u32_KeepAliveTime = 15; // Not applicable here
													 // Area ID
		public const byte S7AreaPE = 0x81;
		public const byte S7AreaPA = 0x82;
		public const byte S7AreaMK = 0x83;
		public const byte S7AreaDB = 0x84;
		public const byte S7AreaCT = 0x1C;
		public const byte S7AreaTM = 0x1D;
		// Word Length
		public const int S7WLBit = 0x01;
		public const int S7WLByte = 0x02;
		public const int S7WLChar = 0x03;
		public const int S7WLWord = 0x04;
		public const int S7WLInt = 0x05;
		public const int S7WLDWord = 0x06;
		public const int S7WLDInt = 0x07;
		public const int S7WLReal = 0x08;
		public const int S7WLCounter = 0x1C;
		public const int S7WLTimer = 0x1D;
		// PLC Status
		public const int S7CpuStatusUnknown = 0x00;
		public const int S7CpuStatusRun = 0x08;
		public const int S7CpuStatusStop = 0x04;

		[StructLayout(LayoutKind.Sequential, Pack = 1)]
		public struct S7Tag
		{
			public Int32 Area;
			public Int32 DBNumber;
			public Int32 Start;
			public Int32 Elements;
			public Int32 WordLen;
		}
		#endregion
	}

	public static class S7
	{
		#region [Help Functions]

		private static Int64 bias = 621355968000000000; // "decimicros" between 0001-01-01 00:00:00 and 1970-01-01 00:00:00

		private static int BCDtoByte(byte B)
		{
			return ((B >> 4) * 10) + (B & 0x0F);
		}

		private static byte ByteToBCD(int Value)
		{
			return (byte)(((Value / 10) << 4) | (Value % 10));
		}

		private static byte[] CopyFrom(byte[] Buffer, int Pos, int Size)
		{
			byte[] Result = new byte[Size];
			Array.Copy(Buffer, Pos, Result, 0, Size);
			return Result;
		}

		public static int DataSizeByte(int WordLength)
		{
			switch (WordLength)
			{
				case S7Consts.S7WLBit: return 1;  // S7 sends 1 byte per bit
				case S7Consts.S7WLByte: return 1;
				case S7Consts.S7WLChar: return 1;
				case S7Consts.S7WLWord: return 2;
				case S7Consts.S7WLDWord: return 4;
				case S7Consts.S7WLInt: return 2;
				case S7Consts.S7WLDInt: return 4;
				case S7Consts.S7WLReal: return 4;
				case S7Consts.S7WLCounter: return 2;
				case S7Consts.S7WLTimer: return 2;
				default: return 0;
			}
		}

		#region Get/Set the bit at Pos.Bit
		public static bool GetBitAt(byte[] Buffer, int Pos, int Bit)
		{
			byte[] Mask = { 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80 };
			if (Bit < 0) Bit = 0;
			if (Bit > 7) Bit = 7;
			return (Buffer[Pos] & Mask[Bit]) != 0;
		}
		public static void SetBitAt(ref byte[] Buffer, int Pos, int Bit, bool Value)
		{
			byte[] Mask = { 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80 };
			if (Bit < 0) Bit = 0;
			if (Bit > 7) Bit = 7;

			if (Value)
				Buffer[Pos] = (byte)(Buffer[Pos] | Mask[Bit]);
			else
				Buffer[Pos] = (byte)(Buffer[Pos] & ~Mask[Bit]);
		}
		#endregion

		#region Get/Set 8 bit signed value (S7 SInt) -128..127
		public static int GetSIntAt(byte[] Buffer, int Pos)
		{
			int Value = Buffer[Pos];
			if (Value < 128)
				return Value;
			else
				return (int)(Value - 256);
		}
		public static void SetSIntAt(byte[] Buffer, int Pos, int Value)
		{
			if (Value < -128) Value = -128;
			if (Value > 127) Value = 127;
			Buffer[Pos] = (byte)Value;
		}
		#endregion

		#region Get/Set 16 bit signed value (S7 int) -32768..32767
		public static int GetIntAt(byte[] Buffer, int Pos)
		{
			return (int)((Buffer[Pos] << 8) | Buffer[Pos + 1]);
		}
		public static void SetIntAt(byte[] Buffer, int Pos, Int16 Value)
		{
			Buffer[Pos] = (byte)(Value >> 8);
			Buffer[Pos + 1] = (byte)(Value & 0x00FF);
		}
		#endregion

		#region Get/Set 32 bit signed value (S7 DInt) -2147483648..2147483647
		public static int GetDIntAt(byte[] Buffer, int Pos)
		{
			int Result;
			Result = Buffer[Pos]; Result <<= 8;
			Result += Buffer[Pos + 1]; Result <<= 8;
			Result += Buffer[Pos + 2]; Result <<= 8;
			Result += Buffer[Pos + 3];
			return Result;
		}
		public static void SetDIntAt(byte[] Buffer, int Pos, int Value)
		{
			Buffer[Pos + 3] = (byte)(Value & 0xFF);
			Buffer[Pos + 2] = (byte)((Value >> 8) & 0xFF);
			Buffer[Pos + 1] = (byte)((Value >> 16) & 0xFF);
			Buffer[Pos] = (byte)((Value >> 24) & 0xFF);
		}
		#endregion

		#region Get/Set 64 bit signed value (S7 LInt) -9223372036854775808..9223372036854775807
		public static Int64 GetLIntAt(byte[] Buffer, int Pos)
		{
			Int64 Result;
			Result = Buffer[Pos]; Result <<= 8;
			Result += Buffer[Pos + 1]; Result <<= 8;
			Result += Buffer[Pos + 2]; Result <<= 8;
			Result += Buffer[Pos + 3]; Result <<= 8;
			Result += Buffer[Pos + 4]; Result <<= 8;
			Result += Buffer[Pos + 5]; Result <<= 8;
			Result += Buffer[Pos + 6]; Result <<= 8;
			Result += Buffer[Pos + 7];
			return Result;
		}
		public static void SetLIntAt(byte[] Buffer, int Pos, Int64 Value)
		{
			Buffer[Pos + 7] = (byte)(Value & 0xFF);
			Buffer[Pos + 6] = (byte)((Value >> 8) & 0xFF);
			Buffer[Pos + 5] = (byte)((Value >> 16) & 0xFF);
			Buffer[Pos + 4] = (byte)((Value >> 24) & 0xFF);
			Buffer[Pos + 3] = (byte)((Value >> 32) & 0xFF);
			Buffer[Pos + 2] = (byte)((Value >> 40) & 0xFF);
			Buffer[Pos + 1] = (byte)((Value >> 48) & 0xFF);
			Buffer[Pos] = (byte)((Value >> 56) & 0xFF);
		}
		#endregion

		#region Get/Set 8 bit unsigned value (S7 USInt) 0..255
		public static byte GetUSIntAt(byte[] Buffer, int Pos)
		{
			return Buffer[Pos];
		}
		public static void SetUSIntAt(byte[] Buffer, int Pos, byte Value)
		{
			Buffer[Pos] = Value;
		}
		#endregion

		#region Get/Set 16 bit unsigned value (S7 UInt) 0..65535
		public static UInt16 GetUIntAt(byte[] Buffer, int Pos)
		{
			return (UInt16)((Buffer[Pos] << 8) | Buffer[Pos + 1]);
		}
		public static void SetUIntAt(byte[] Buffer, int Pos, UInt16 Value)
		{
			Buffer[Pos] = (byte)(Value >> 8);
			Buffer[Pos + 1] = (byte)(Value & 0x00FF);
		}
		#endregion

		#region Get/Set 32 bit unsigned value (S7 UDInt) 0..4294967296
		public static UInt32 GetUDIntAt(byte[] Buffer, int Pos)
		{
			UInt32 Result;
			Result = Buffer[Pos]; Result <<= 8;
			Result |= Buffer[Pos + 1]; Result <<= 8;
			Result |= Buffer[Pos + 2]; Result <<= 8;
			Result |= Buffer[Pos + 3];
			return Result;
		}
		public static void SetUDIntAt(byte[] Buffer, int Pos, UInt32 Value)
		{
			Buffer[Pos + 3] = (byte)(Value & 0xFF);
			Buffer[Pos + 2] = (byte)((Value >> 8) & 0xFF);
			Buffer[Pos + 1] = (byte)((Value >> 16) & 0xFF);
			Buffer[Pos] = (byte)((Value >> 24) & 0xFF);
		}
		#endregion

		#region Get/Set 64 bit unsigned value (S7 ULint) 0..18446744073709551616
		public static UInt64 GetULIntAt(byte[] Buffer, int Pos)
		{
			UInt64 Result;
			Result = Buffer[Pos]; Result <<= 8;
			Result |= Buffer[Pos + 1]; Result <<= 8;
			Result |= Buffer[Pos + 2]; Result <<= 8;
			Result |= Buffer[Pos + 3]; Result <<= 8;
			Result |= Buffer[Pos + 4]; Result <<= 8;
			Result |= Buffer[Pos + 5]; Result <<= 8;
			Result |= Buffer[Pos + 6]; Result <<= 8;
			Result |= Buffer[Pos + 7];
			return Result;
		}
		public static void SetULintAt(byte[] Buffer, int Pos, UInt64 Value)
		{
			Buffer[Pos + 7] = (byte)(Value & 0xFF);
			Buffer[Pos + 6] = (byte)((Value >> 8) & 0xFF);
			Buffer[Pos + 5] = (byte)((Value >> 16) & 0xFF);
			Buffer[Pos + 4] = (byte)((Value >> 24) & 0xFF);
			Buffer[Pos + 3] = (byte)((Value >> 32) & 0xFF);
			Buffer[Pos + 2] = (byte)((Value >> 40) & 0xFF);
			Buffer[Pos + 1] = (byte)((Value >> 48) & 0xFF);
			Buffer[Pos] = (byte)((Value >> 56) & 0xFF);
		}
		#endregion

		#region Get/Set 8 bit word (S7 Byte) 16#00..16#FF
		public static byte GetByteAt(byte[] Buffer, int Pos)
		{
			return Buffer[Pos];
		}
		public static void SetByteAt(byte[] Buffer, int Pos, byte Value)
		{
			Buffer[Pos] = Value;
		}
		#endregion

		#region Get/Set 16 bit word (S7 Word) 16#0000..16#FFFF
		public static UInt16 GetWordAt(byte[] Buffer, int Pos)
		{
			return GetUIntAt(Buffer, Pos);
		}
		public static void SetWordAt(byte[] Buffer, int Pos, UInt16 Value)
		{
			SetUIntAt(Buffer, Pos, Value);
		}
		#endregion

		#region Get/Set 32 bit word (S7 DWord) 16#00000000..16#FFFFFFFF
		public static UInt32 GetDWordAt(byte[] Buffer, int Pos)
		{
			return GetUDIntAt(Buffer, Pos);
		}
		public static void SetDWordAt(byte[] Buffer, int Pos, UInt32 Value)
		{
			SetUDIntAt(Buffer, Pos, Value);
		}
		#endregion

		#region Get/Set 64 bit word (S7 LWord) 16#0000000000000000..16#FFFFFFFFFFFFFFFF
		public static UInt64 GetLWordAt(byte[] Buffer, int Pos)
		{
			return GetULIntAt(Buffer, Pos);
		}
		public static void SetLWordAt(byte[] Buffer, int Pos, UInt64 Value)
		{
			SetULintAt(Buffer, Pos, Value);
		}
		#endregion

		#region Get/Set 32 bit floating point number (S7 Real) (Range of Single)
		public static Single GetRealAt(byte[] Buffer, int Pos)
		{
			UInt32 Value = GetUDIntAt(Buffer, Pos);
			byte[] bytes = BitConverter.GetBytes(Value);
			return BitConverter.ToSingle(bytes, 0);
		}
		public static void SetRealAt(byte[] Buffer, int Pos, Single Value)
		{
			byte[] FloatArray = BitConverter.GetBytes(Value);
			Buffer[Pos] = FloatArray[3];
			Buffer[Pos + 1] = FloatArray[2];
			Buffer[Pos + 2] = FloatArray[1];
			Buffer[Pos + 3] = FloatArray[0];
		}
		#endregion

		#region Get/Set 64 bit floating point number (S7 LReal) (Range of Double)
		public static Double GetLRealAt(byte[] Buffer, int Pos)
		{
			UInt64 Value = GetULIntAt(Buffer, Pos);
			byte[] bytes = BitConverter.GetBytes(Value);
			return BitConverter.ToDouble(bytes, 0);
		}
		public static void SetLRealAt(byte[] Buffer, int Pos, Double Value)
		{
			byte[] FloatArray = BitConverter.GetBytes(Value);
			Buffer[Pos] = FloatArray[7];
			Buffer[Pos + 1] = FloatArray[6];
			Buffer[Pos + 2] = FloatArray[5];
			Buffer[Pos + 3] = FloatArray[4];
			Buffer[Pos + 4] = FloatArray[3];
			Buffer[Pos + 5] = FloatArray[2];
			Buffer[Pos + 6] = FloatArray[1];
			Buffer[Pos + 7] = FloatArray[0];
		}
		#endregion

		#region Get/Set DateTime (S7 DATE_AND_TIME)
		public static DateTime GetDateTimeAt(byte[] Buffer, int Pos)
		{
			int Year, Month, Day, Hour, Min, Sec, MSec;

			Year = BCDtoByte(Buffer[Pos]);
			if (Year < 90)
				Year += 2000;
			else
				Year += 1900;

			Month = BCDtoByte(Buffer[Pos + 1]);
			Day = BCDtoByte(Buffer[Pos + 2]);
			Hour = BCDtoByte(Buffer[Pos + 3]);
			Min = BCDtoByte(Buffer[Pos + 4]);
			Sec = BCDtoByte(Buffer[Pos + 5]);
			MSec = (BCDtoByte(Buffer[Pos + 6]) * 10) + (BCDtoByte(Buffer[Pos + 7]) / 10);
			try
			{
				return new DateTime(Year, Month, Day, Hour, Min, Sec, MSec);
			}
			catch (System.ArgumentOutOfRangeException)
			{
				return new DateTime(0);
			}
		}
		public static void SetDateTimeAt(byte[] Buffer, int Pos, DateTime Value)
		{
			int Year = Value.Year;
			int Month = Value.Month;
			int Day = Value.Day;
			int Hour = Value.Hour;
			int Min = Value.Minute;
			int Sec = Value.Second;
			int Dow = (int)Value.DayOfWeek + 1;
			// MSecH = First two digits of miliseconds 
			int MsecH = Value.Millisecond / 10;
			// MSecL = Last digit of miliseconds
			int MsecL = Value.Millisecond % 10;
			if (Year > 1999)
				Year -= 2000;

			Buffer[Pos] = ByteToBCD(Year);
			Buffer[Pos + 1] = ByteToBCD(Month);
			Buffer[Pos + 2] = ByteToBCD(Day);
			Buffer[Pos + 3] = ByteToBCD(Hour);
			Buffer[Pos + 4] = ByteToBCD(Min);
			Buffer[Pos + 5] = ByteToBCD(Sec);
			Buffer[Pos + 6] = ByteToBCD(MsecH);
			Buffer[Pos + 7] = ByteToBCD(MsecL * 10 + Dow);
		}
		#endregion

		#region Get/Set DATE (S7 DATE) 
		public static DateTime GetDateAt(byte[] Buffer, int Pos)
		{
			try
			{
				return new DateTime(1990, 1, 1).AddDays(GetIntAt(Buffer, Pos));
			}
			catch (System.ArgumentOutOfRangeException)
			{
				return new DateTime(0);
			}
		}
		public static void SetDateAt(byte[] Buffer, int Pos, DateTime Value)
		{
			SetIntAt(Buffer, Pos, (Int16)(Value - new DateTime(1990, 1, 1)).Days);
		}

		#endregion

		#region Get/Set TOD (S7 TIME_OF_DAY)
		public static DateTime GetTODAt(byte[] Buffer, int Pos)
		{
			try
			{
				return new DateTime(0).AddMilliseconds(S7.GetDIntAt(Buffer, Pos));
			}
			catch (System.ArgumentOutOfRangeException)
			{
				return new DateTime(0);
			}
		}
		public static void SetTODAt(byte[] Buffer, int Pos, DateTime Value)
		{
			TimeSpan Time = Value.TimeOfDay;
			SetDIntAt(Buffer, Pos, (Int32)Math.Round(Time.TotalMilliseconds));
		}
		#endregion

		#region Get/Set LTOD (S7 1500 LONG TIME_OF_DAY)
		public static DateTime GetLTODAt(byte[] Buffer, int Pos)
		{
			// .NET Tick = 100 ns, S71500 Tick = 1 ns
			try
			{
				return new DateTime(Math.Abs(GetLIntAt(Buffer, Pos) / 100));
			}
			catch (System.ArgumentOutOfRangeException)
			{
				return new DateTime(0);
			}
		}
		public static void SetLTODAt(byte[] Buffer, int Pos, DateTime Value)
		{
			TimeSpan Time = Value.TimeOfDay;
			SetLIntAt(Buffer, Pos, (Int64)Time.Ticks * 100);
		}
		#endregion

		#region GET/SET LDT (S7 1500 Long Date and Time)
		public static DateTime GetLDTAt(byte[] Buffer, int Pos)
		{
			try
			{
				return new DateTime((GetLIntAt(Buffer, Pos) / 100) + bias);
			}
			catch (System.ArgumentOutOfRangeException)
			{
				return new DateTime(0);
			}
		}
		public static void SetLDTAt(byte[] Buffer, int Pos, DateTime Value)
		{
			SetLIntAt(Buffer, Pos, (Value.Ticks - bias) * 100);
		}
		#endregion

		#region Get/Set DTL (S71200/1500 Date and Time)
		// Thanks to Johan Cardoen for GetDTLAt
		public static DateTime GetDTLAt(byte[] Buffer, int Pos)
		{
			int Year, Month, Day, Hour, Min, Sec, MSec;

			Year = Buffer[Pos] * 256 + Buffer[Pos + 1];
			Month = Buffer[Pos + 2];
			Day = Buffer[Pos + 3];
			Hour = Buffer[Pos + 5];
			Min = Buffer[Pos + 6];
			Sec = Buffer[Pos + 7];
			MSec = (int)GetUDIntAt(Buffer, Pos + 8) / 1000000;

			try
			{
				return new DateTime(Year, Month, Day, Hour, Min, Sec, MSec);
			}
			catch (System.ArgumentOutOfRangeException)
			{
				return new DateTime(0);
			}
		}
		public static void SetDTLAt(byte[] Buffer, int Pos, DateTime Value)
		{
			short Year = (short)Value.Year;
			byte Month = (byte)Value.Month;
			byte Day = (byte)Value.Day;
			byte Hour = (byte)Value.Hour;
			byte Min = (byte)Value.Minute;
			byte Sec = (byte)Value.Second;
			byte Dow = (byte)(Value.DayOfWeek + 1);

			Int32 NanoSecs = Value.Millisecond * 1000000;

			var bytes_short = BitConverter.GetBytes(Year);

			Buffer[Pos] = bytes_short[1];
			Buffer[Pos + 1] = bytes_short[0];
			Buffer[Pos + 2] = Month;
			Buffer[Pos + 3] = Day;
			Buffer[Pos + 4] = Dow;
			Buffer[Pos + 5] = Hour;
			Buffer[Pos + 6] = Min;
			Buffer[Pos + 7] = Sec;
			SetDIntAt(Buffer, Pos + 8, NanoSecs);
		}

		#endregion

		#region Get/Set String (S7 String)
		// Thanks to Pablo Agirre 
		public static string GetStringAt(byte[] Buffer, int Pos)
		{
			int size = (int)Buffer[Pos + 1];
			return Encoding.UTF8.GetString(Buffer, Pos + 2, size);
		}
		public static void SetStringAt(byte[] Buffer, int Pos, int MaxLen, string Value)
		{
			int size = Value.Length;
			Buffer[Pos] = (byte)MaxLen;
			Buffer[Pos + 1] = (byte)size;
			Encoding.UTF8.GetBytes(Value, 0, size, Buffer, Pos + 2);
		}
		#endregion

		#region Get/Set Array of char (S7 ARRAY OF CHARS)
		public static string GetCharsAt(byte[] Buffer, int Pos, int Size)
		{
			return Encoding.UTF8.GetString(Buffer, Pos, Size);
		}
		public static void SetCharsAt(byte[] Buffer, int Pos, string Value)
		{
			int MaxLen = Buffer.Length - Pos;
			// Truncs the string if there's no room enough        
			if (MaxLen > Value.Length) MaxLen = Value.Length;
			Encoding.UTF8.GetBytes(Value, 0, MaxLen, Buffer, Pos);
		}
		#endregion

		#region Get/Set Counter
		public static int GetCounter(ushort Value)
		{
			return BCDtoByte((byte)Value) * 100 + BCDtoByte((byte)(Value >> 8));
		}

		public static int GetCounterAt(ushort[] Buffer, int Index)
		{
			return GetCounter(Buffer[Index]);
		}

		public static ushort ToCounter(int Value)
		{
			return (ushort)(ByteToBCD(Value / 100) + (ByteToBCD(Value % 100) << 8));
		}

		public static void SetCounterAt(ushort[] Buffer, int Pos, int Value)
		{
			Buffer[Pos] = ToCounter(Value);
		}
		#endregion

		#endregion [Help Functions]
	}

	public class S7MultiVar
	{
		#region [MultiRead/Write Helper]
		private S7Client FClient;
		private GCHandle[] Handles = new GCHandle[S7Client.MaxVars];
		private int Count = 0;
		private S7Client.S7DataItem[] Items = new S7Client.S7DataItem[S7Client.MaxVars];


		public int[] Results = new int[S7Client.MaxVars];

		private bool AdjustWordLength(int Area, ref int WordLen, ref int Amount, ref int Start)
		{
			// Calc Word size          
			int WordSize = S7.DataSizeByte(WordLen);
			if (WordSize == 0)
				return false;

			if (Area == S7Consts.S7AreaCT)
				WordLen = S7Consts.S7WLCounter;
			if (Area == S7Consts.S7AreaTM)
				WordLen = S7Consts.S7WLTimer;

			if (WordLen == S7Consts.S7WLBit)
				Amount = 1;  // Only 1 bit can be transferred at time
			else
			{
				if ((WordLen != S7Consts.S7WLCounter) && (WordLen != S7Consts.S7WLTimer))
				{
					Amount = Amount * WordSize;
					Start = Start * 8;
					WordLen = S7Consts.S7WLByte;
				}
			}
			return true;
		}

		public S7MultiVar(S7Client Client)
		{
			FClient = Client;
			for (int c = 0; c < S7Client.MaxVars; c++)
				Results[c] = (int)S7Consts.errCliItemNotAvailable;
		}
		~S7MultiVar()
		{
			Clear();
		}

		public bool Add<T>(S7Consts.S7Tag Tag, ref T[] Buffer, int Offset)
		{
			return Add(Tag.Area, Tag.WordLen, Tag.DBNumber, Tag.Start, Tag.Elements, ref Buffer, Offset);
		}

		public bool Add<T>(S7Consts.S7Tag Tag, ref T[] Buffer)
		{
			return Add(Tag.Area, Tag.WordLen, Tag.DBNumber, Tag.Start, Tag.Elements, ref Buffer);
		}

		public bool Add<T>(Int32 Area, Int32 WordLen, Int32 DBNumber, Int32 Start, Int32 Amount, ref T[] Buffer)
		{
			return Add(Area, WordLen, DBNumber, Start, Amount, ref Buffer, 0);
		}

		public bool Add<T>(Int32 Area, Int32 WordLen, Int32 DBNumber, Int32 Start, Int32 Amount, ref T[] Buffer, int Offset)
		{
			if (Count < S7Client.MaxVars)
			{
				if (AdjustWordLength(Area, ref WordLen, ref Amount, ref Start))
				{
					Items[Count].Area = Area;
					Items[Count].WordLen = WordLen;
					Items[Count].Result = (int)S7Consts.errCliItemNotAvailable;
					Items[Count].DBNumber = DBNumber;
					Items[Count].Start = Start;
					Items[Count].Amount = Amount;
					GCHandle handle = GCHandle.Alloc(Buffer, GCHandleType.Pinned);
#if WINDOWS_UWP || NETFX_CORE
                    if (IntPtr.Size == 4)
                        Items[Count].pData = (IntPtr)(handle.AddrOfPinnedObject().ToInt32() + Offset * Marshal.SizeOf<T>());
                    else
                        Items[Count].pData = (IntPtr)(handle.AddrOfPinnedObject().ToInt64() + Offset * Marshal.SizeOf<T>());
#else
					if (IntPtr.Size == 4)
						Items[Count].pData = (IntPtr)(handle.AddrOfPinnedObject().ToInt32() + Offset * Marshal.SizeOf(typeof(T)));
					else
						Items[Count].pData = (IntPtr)(handle.AddrOfPinnedObject().ToInt64() + Offset * Marshal.SizeOf(typeof(T)));
#endif
					Handles[Count] = handle;
					Count++;
					return true;
				}
				else
					return false;
			}
			else
				return false;
		}
        public bool AddCDL<T>(S7Consts.S7Tag Tag, ref T[] Buffer, int Offset)
        {
            return AddCDL(Tag.Area, Tag.WordLen, Tag.DBNumber, Tag.Start, Tag.Elements, ref Buffer, Offset);
        }
        public bool AddCDL<T>(Int32 Area, Int32 WordLen, Int32 DBNumber, Int32 Start, Int32 Amount, ref T[] Buffer, int Offset)
        {
            if (Count < S7Client.MaxVars)
            {
                if (true)
                {
                    Items[Count].Area = Area;
                    Items[Count].WordLen = WordLen;
                    Items[Count].Result = (int)S7Consts.errCliItemNotAvailable;
                    Items[Count].DBNumber = DBNumber;
                    Items[Count].Start = Start;
                    Items[Count].Amount = Amount;
                    GCHandle handle = GCHandle.Alloc(Buffer, GCHandleType.Pinned);
#if WINDOWS_UWP || NETFX_CORE
                    if (IntPtr.Size == 4)
                        Items[Count].pData = (IntPtr)(handle.AddrOfPinnedObject().ToInt32() + Offset * Marshal.SizeOf<T>());
                    else
                        Items[Count].pData = (IntPtr)(handle.AddrOfPinnedObject().ToInt64() + Offset * Marshal.SizeOf<T>());
#else
                    if (IntPtr.Size == 4)
                        Items[Count].pData = (IntPtr)(handle.AddrOfPinnedObject().ToInt32() + Offset * Marshal.SizeOf(typeof(T)));
                    else
                        Items[Count].pData = (IntPtr)(handle.AddrOfPinnedObject().ToInt64() + Offset * Marshal.SizeOf(typeof(T)));
#endif
                    Handles[Count] = handle;
                    Count++;
                    return true;
                }
                else
                    return false;
            }
            else
                return false;
        }

        public int Read()
		{
			int FunctionResult;
			int GlobalResult = (int)S7Consts.errCliFunctionRefused;
			try
			{
				if (Count > 0)
				{
					FunctionResult = FClient.ReadMultiVars(Items, Count);
					if (FunctionResult == 0)
						for (int c = 0; c < S7Client.MaxVars; c++)
							Results[c] = Items[c].Result;
					GlobalResult = FunctionResult;
				}
				else
					GlobalResult = (int)S7Consts.errCliFunctionRefused;
			}
			finally
			{
				Clear(); // handles are no more needed and MUST be freed
			}
			return GlobalResult;
		}

		public int Write()
		{
			int FunctionResult;
			int GlobalResult = (int)S7Consts.errCliFunctionRefused;
			try
			{
				if (Count > 0)
				{
					FunctionResult = FClient.WriteMultiVars(Items, Count);
					if (FunctionResult == 0)
						for (int c = 0; c < S7Client.MaxVars; c++)
							Results[c] = Items[c].Result;
					GlobalResult = FunctionResult;
				}
				else
					GlobalResult = (int)S7Consts.errCliFunctionRefused;
			}
			finally
			{
				Clear(); // handles are no more needed and MUST be freed
			}
			return GlobalResult;
		}

		public void Clear()
		{
			for (int c = 0; c < Count; c++)
			{
				if (Handles[c] != null)
					Handles[c].Free();
			}
			Count = 0;
		}
		#endregion
	}

	public class S7Client
	{
		#region [Constants and TypeDefs]

		// Block type
		public const int Block_OB = 0x38;
		public const int Block_DB = 0x41;
		public const int Block_SDB = 0x42;
		public const int Block_FC = 0x43;
		public const int Block_SFC = 0x44;
		public const int Block_FB = 0x45;
		public const int Block_SFB = 0x46;

		// Sub Block Type 
		public const byte SubBlk_OB = 0x08;
		public const byte SubBlk_DB = 0x0A;
		public const byte SubBlk_SDB = 0x0B;
		public const byte SubBlk_FC = 0x0C;
		public const byte SubBlk_SFC = 0x0D;
		public const byte SubBlk_FB = 0x0E;
		public const byte SubBlk_SFB = 0x0F;

		// Block languages
		public const byte BlockLangAWL = 0x01;
		public const byte BlockLangKOP = 0x02;
		public const byte BlockLangFUP = 0x03;
		public const byte BlockLangSCL = 0x04;
		public const byte BlockLangDB = 0x05;
		public const byte BlockLangGRAPH = 0x06;

		// Max number of vars (multiread/write)
		public static readonly int MaxVars = 20;

		// Result transport size
		const byte TS_ResBit = 0x03;
		const byte TS_ResByte = 0x04;
		const byte TS_ResInt = 0x05;
		const byte TS_ResReal = 0x07;
		const byte TS_ResOctet = 0x09;

		const ushort Code7Ok = 0x0000;
		const ushort Code7AddressOutOfRange = 0x0005;
		const ushort Code7InvalidTransportSize = 0x0006;
		const ushort Code7WriteDataSizeMismatch = 0x0007;
		const ushort Code7ResItemNotAvailable = 0x000A;
		const ushort Code7ResItemNotAvailable1 = 0xD209;
		const ushort Code7InvalidValue = 0xDC01;
		const ushort Code7NeedPassword = 0xD241;
		const ushort Code7InvalidPassword = 0xD602;
		const ushort Code7NoPasswordToClear = 0xD604;
		const ushort Code7NoPasswordToSet = 0xD605;
		const ushort Code7FunNotAvailable = 0x8104;
		const ushort Code7DataOverPDU = 0x8500;

		// Client Connection Type
		public static readonly UInt16 CONNTYPE_PG = 0x01;  // Connect to the PLC as a PG
		public static readonly UInt16 CONNTYPE_OP = 0x02;  // Connect to the PLC as an OP
		public static readonly UInt16 CONNTYPE_BASIC = 0x03;  // Basic connection 

		public int _LastError = 0;

		public struct S7DataItem
		{
			public int Area;
			public int WordLen;
			public int Result;
			public int DBNumber;
			public int Start;
			public int Amount;
			public IntPtr pData;
		}

		// Order Code + Version
		public struct S7OrderCode
		{
			public string Code; // such as "6ES7 151-8AB01-0AB0"
			public byte V1;     // Version 1st digit
			public byte V2;     // Version 2nd digit
			public byte V3;     // Version 3th digit
		};

		// CPU Info
		public struct S7CpuInfo
		{
			public string ModuleTypeName;
			public string SerialNumber;
			public string ASName;
			public string Copyright;
			public string ModuleName;
		}

		public struct S7CpInfo
		{
			public int MaxPduLength;
			public int MaxConnections;
			public int MaxMpiRate;
			public int MaxBusRate;
		};

		// Block List
		[StructLayout(LayoutKind.Sequential, Pack = 1)]
		public struct S7BlocksList
		{
			public Int32 OBCount;
			public Int32 FBCount;
			public Int32 FCCount;
			public Int32 SFBCount;
			public Int32 SFCCount;
			public Int32 DBCount;
			public Int32 SDBCount;
		};

		// Managed Block Info
		public struct S7BlockInfo
		{
			public int BlkType;
			public int BlkNumber;
			public int BlkLang;
			public int BlkFlags;
			public int MC7Size;  // The real size in bytes
			public int LoadSize;
			public int LocalData;
			public int SBBLength;
			public int CheckSum;
			public int Version;
			// Chars info
			public string CodeDate;
			public string IntfDate;
			public string Author;
			public string Family;
			public string Header;
		};

		// See §33.1 of "System Software for S7-300/400 System and Standard Functions"
		// and see SFC51 description too
		[StructLayout(LayoutKind.Sequential, Pack = 1)]
		public struct SZL_HEADER
		{
			public UInt16 LENTHDR;
			public UInt16 N_DR;
		};

		[StructLayout(LayoutKind.Sequential, Pack = 1)]
		public struct S7SZL
		{
			public SZL_HEADER Header;
			[MarshalAs(UnmanagedType.ByValArray)]
			public byte[] Data;
		};

		// SZL List of available SZL IDs : same as SZL but List items are big-endian adjusted
		[StructLayout(LayoutKind.Sequential, Pack = 1)]
		public struct S7SZLList
		{
			public SZL_HEADER Header;
			[MarshalAs(UnmanagedType.ByValArray, SizeConst = 0x2000 - 2)]
			public UInt16[] Data;
		};

		// S7 Protection
		// See §33.19 of "System Software for S7-300/400 System and Standard Functions"
		public struct S7Protection
		{
			public ushort sch_schal;
			public ushort sch_par;
			public ushort sch_rel;
			public ushort bart_sch;
			public ushort anl_sch;
		};

		#endregion

		#region [S7 Telegrams]

		// ISO Connection Request telegram (contains also ISO Header and COTP Header)
		byte[] ISO_CR = {
            // TPKT (RFC1006 Header)
            0x03, // RFC 1006 ID (3) 
            0x00, // Reserved, always 0
            0x00, // High part of packet lenght (entire frame, payload and TPDU included)
            0x16, // Low part of packet lenght (entire frame, payload and TPDU included)
            // COTP (ISO 8073 Header)
            0x11, // PDU Size Length
            0xE0, // CR - Connection Request ID
            0x00, // Dst Reference HI
            0x00, // Dst Reference LO
            0x00, // Src Reference HI
            0x01, // Src Reference LO
            0x00, // Class + Options Flags
            0xC0, // PDU Max Length ID
            0x01, // PDU Max Length HI
            0x0A, // PDU Max Length LO
            0xC1, // Src TSAP Identifier
            0x02, // Src TSAP Length (2 bytes)
            0x01, // Src TSAP HI (will be overwritten)
            0x00, // Src TSAP LO (will be overwritten)
            0xC2, // Dst TSAP Identifier
            0x02, // Dst TSAP Length (2 bytes)
            0x01, // Dst TSAP HI (will be overwritten)
            0x02  // Dst TSAP LO (will be overwritten)
        };

		// TPKT + ISO COTP Header (Connection Oriented Transport Protocol)
		byte[] TPKT_ISO = { // 7 bytes
            0x03,0x00,
			0x00,0x1f,      // Telegram Length (Data Size + 31 or 35)
            0x02,0xf0,0x80  // COTP (see above for info)
        };

		// S7 PDU Negotiation Telegram (contains also ISO Header and COTP Header)
		byte[] S7_PN = {
			0x03, 0x00, 0x00, 0x19,
			0x02, 0xf0, 0x80, // TPKT + COTP (see above for info)
            0x32, 0x01, 0x00, 0x00,
			0x04, 0x00, 0x00, 0x08,
			0x00, 0x00, 0xf0, 0x00,
			0x00, 0x01, 0x00, 0x01,
			0x00, 0x1e        // PDU Length Requested = HI-LO Here Default 480 bytes
        };

		// S7 Read/Write Request Header (contains also ISO Header and COTP Header)
		byte[] S7_RW = { // 31-35 bytes
            0x03,0x00,
			0x00,0x1f,       // Telegram Length (Data Size + 31 or 35)
            0x02,0xf0, 0x80, // COTP (see above for info)
            0x32,            // S7 Protocol ID 
            0x01,            // Job Type
            0x00,0x00,       // Redundancy identification
            0x05,0x00,       // PDU Reference
            0x00,0x0e,       // Parameters Length
            0x00,0x00,       // Data Length = Size(bytes) + 4      
            0x04,            // Function 4 Read Var, 5 Write Var  
            0x01,            // Items count
            0x12,            // Var spec.
            0x0a,            // Length of remaining bytes
            0x10,            // Syntax ID 
            (byte)S7Consts.S7WLByte,  // Transport Size idx=22                       
            0x00,0x00,       // Num Elements                          
            0x00,0x00,       // DB Number (if any, else 0)            
            0x84,            // Area Type                            
            0x00,0x00,0x00,  // Area Offset                     
            // WR area
            0x00,            // Reserved 
            0x04,            // Transport size
            0x00,0x00,       // Data Length * 8 (if not bit or timer or counter) 
        };
		private static int Size_RD = 31; // Header Size when Reading 
		private static int Size_WR = 35; // Header Size when Writing

		// S7 Variable MultiRead Header
		byte[] S7_MRD_HEADER = {
			0x03,0x00,
			0x00,0x1f,       // Telegram Length 
            0x02,0xf0, 0x80, // COTP (see above for info)
            0x32,            // S7 Protocol ID 
            0x01,            // Job Type
            0x00,0x00,       // Redundancy identification
            0x05,0x00,       // PDU Reference
            0x00,0x0e,       // Parameters Length
            0x00,0x00,       // Data Length = Size(bytes) + 4      
            0x04,            // Function 4 Read Var, 5 Write Var  
            0x01             // Items count (idx 18)
        };

		// S7 Variable MultiRead Item
		byte[] S7_MRD_ITEM = {
			0x12,            // Var spec.
            0x0a,            // Length of remaining bytes
            0x10,            // Syntax ID 
            (byte)S7Consts.S7WLByte,  // Transport Size idx=3                   
            0x00,0x00,       // Num Elements                          
            0x00,0x00,       // DB Number (if any, else 0)            
            0x84,            // Area Type                            
            0x00,0x00,0x00   // Area Offset                     
        };

		// S7 Variable MultiWrite Header
		byte[] S7_MWR_HEADER = {
			0x03,0x00,
			0x00,0x1f,       // Telegram Length 
            0x02,0xf0, 0x80, // COTP (see above for info)
            0x32,            // S7 Protocol ID 
            0x01,            // Job Type
            0x00,0x00,       // Redundancy identification
            0x05,0x00,       // PDU Reference
            0x00,0x0e,       // Parameters Length (idx 13)
            0x00,0x00,       // Data Length = Size(bytes) + 4 (idx 15)     
            0x05,            // Function 5 Write Var  
            0x01             // Items count (idx 18)
        };

		// S7 Variable MultiWrite Item (Param)
		byte[] S7_MWR_PARAM = {
			0x12,            // Var spec.
            0x0a,            // Length of remaining bytes
            0x10,            // Syntax ID 
            (byte)S7Consts.S7WLByte,  // Transport Size idx=3                      
            0x00,0x00,       // Num Elements                          
            0x00,0x00,       // DB Number (if any, else 0)            
            0x84,            // Area Type                            
            0x00,0x00,0x00,  // Area Offset                     
        };

		// SZL First telegram request   
		byte[] S7_SZL_FIRST = {
			0x03, 0x00, 0x00, 0x21,
			0x02, 0xf0, 0x80, 0x32,
			0x07, 0x00, 0x00,
			0x05, 0x00, // Sequence out
            0x00, 0x08, 0x00,
			0x08, 0x00, 0x01, 0x12,
			0x04, 0x11, 0x44, 0x01,
			0x00, 0xff, 0x09, 0x00,
			0x04,
			0x00, 0x00, // ID (29)
            0x00, 0x00  // Index (31)
        };

		// SZL Next telegram request 
		byte[] S7_SZL_NEXT = {
			0x03, 0x00, 0x00, 0x21,
			0x02, 0xf0, 0x80, 0x32,
			0x07, 0x00, 0x00, 0x06,
			0x00, 0x00, 0x0c, 0x00,
			0x04, 0x00, 0x01, 0x12,
			0x08, 0x12, 0x44, 0x01,
			0x01, // Sequence
            0x00, 0x00, 0x00, 0x00,
			0x0a, 0x00, 0x00, 0x00
		};

		// Get Date/Time request
		byte[] S7_GET_DT = {
			0x03, 0x00, 0x00, 0x1d,
			0x02, 0xf0, 0x80, 0x32,
			0x07, 0x00, 0x00, 0x38,
			0x00, 0x00, 0x08, 0x00,
			0x04, 0x00, 0x01, 0x12,
			0x04, 0x11, 0x47, 0x01,
			0x00, 0x0a, 0x00, 0x00,
			0x00
		};

		// Set Date/Time command
		byte[] S7_SET_DT = {
			0x03, 0x00, 0x00, 0x27,
			0x02, 0xf0, 0x80, 0x32,
			0x07, 0x00, 0x00, 0x89,
			0x03, 0x00, 0x08, 0x00,
			0x0e, 0x00, 0x01, 0x12,
			0x04, 0x11, 0x47, 0x02,
			0x00, 0xff, 0x09, 0x00,
			0x0a, 0x00,
			0x19, // Hi part of Year (idx=30)
            0x13, // Lo part of Year
            0x12, // Month
            0x06, // Day
            0x17, // Hour
            0x37, // Min
            0x13, // Sec
            0x00, 0x01 // ms + Day of week   
        };

		// S7 Set Session Password 
		byte[] S7_SET_PWD = {
			0x03, 0x00, 0x00, 0x25,
			0x02, 0xf0, 0x80, 0x32,
			0x07, 0x00, 0x00, 0x27,
			0x00, 0x00, 0x08, 0x00,
			0x0c, 0x00, 0x01, 0x12,
			0x04, 0x11, 0x45, 0x01,
			0x00, 0xff, 0x09, 0x00,
			0x08, 
            // 8 Char Encoded Password
            0x00, 0x00, 0x00, 0x00,
			0x00, 0x00, 0x00, 0x00
		};

		// S7 Clear Session Password 
		byte[] S7_CLR_PWD = {
			0x03, 0x00, 0x00, 0x1d,
			0x02, 0xf0, 0x80, 0x32,
			0x07, 0x00, 0x00, 0x29,
			0x00, 0x00, 0x08, 0x00,
			0x04, 0x00, 0x01, 0x12,
			0x04, 0x11, 0x45, 0x02,
			0x00, 0x0a, 0x00, 0x00,
			0x00
		};

		// S7 STOP request
		byte[] S7_STOP = {
			0x03, 0x00, 0x00, 0x21,
			0x02, 0xf0, 0x80, 0x32,
			0x01, 0x00, 0x00, 0x0e,
			0x00, 0x00, 0x10, 0x00,
			0x00, 0x29, 0x00, 0x00,
			0x00, 0x00, 0x00, 0x09,
			0x50, 0x5f, 0x50, 0x52,
			0x4f, 0x47, 0x52, 0x41,
			0x4d
		};

		// S7 HOT Start request
		byte[] S7_HOT_START = {
			0x03, 0x00, 0x00, 0x25,
			0x02, 0xf0, 0x80, 0x32,
			0x01, 0x00, 0x00, 0x0c,
			0x00, 0x00, 0x14, 0x00,
			0x00, 0x28, 0x00, 0x00,
			0x00, 0x00, 0x00, 0x00,
			0xfd, 0x00, 0x00, 0x09,
			0x50, 0x5f, 0x50, 0x52,
			0x4f, 0x47, 0x52, 0x41,
			0x4d
		};

		// S7 COLD Start request
		byte[] S7_COLD_START = {
			0x03, 0x00, 0x00, 0x27,
			0x02, 0xf0, 0x80, 0x32,
			0x01, 0x00, 0x00, 0x0f,
			0x00, 0x00, 0x16, 0x00,
			0x00, 0x28, 0x00, 0x00,
			0x00, 0x00, 0x00, 0x00,
			0xfd, 0x00, 0x02, 0x43,
			0x20, 0x09, 0x50, 0x5f,
			0x50, 0x52, 0x4f, 0x47,
			0x52, 0x41, 0x4d
		};
		const byte pduStart = 0x28;   // CPU start
		const byte pduStop = 0x29;   // CPU stop
		const byte pduAlreadyStarted = 0x02;   // CPU already in run mode
		const byte pduAlreadyStopped = 0x07;   // CPU already in stop mode

		// S7 Get PLC Status 
		byte[] S7_GET_STAT = {
			0x03, 0x00, 0x00, 0x21,
			0x02, 0xf0, 0x80, 0x32,
			0x07, 0x00, 0x00, 0x2c,
			0x00, 0x00, 0x08, 0x00,
			0x08, 0x00, 0x01, 0x12,
			0x04, 0x11, 0x44, 0x01,
			0x00, 0xff, 0x09, 0x00,
			0x04, 0x04, 0x24, 0x00,
			0x00
		};

		// S7 Get Block Info Request Header (contains also ISO Header and COTP Header)
		byte[] S7_BI = {
			0x03, 0x00, 0x00, 0x25,
			0x02, 0xf0, 0x80, 0x32,
			0x07, 0x00, 0x00, 0x05,
			0x00, 0x00, 0x08, 0x00,
			0x0c, 0x00, 0x01, 0x12,
			0x04, 0x11, 0x43, 0x03,
			0x00, 0xff, 0x09, 0x00,
			0x08, 0x30,
			0x41, // Block Type
            0x30, 0x30, 0x30, 0x30, 0x30, // ASCII Block Number
            0x41
		};

		#endregion

		#region [Internals]

		// Defaults
		private static int ISOTCP = 102; // ISOTCP Port
		private static int MinPduSize = 16;
		private static int MinPduSizeToRequest = 240;
		private static int MaxPduSizeToRequest = 960;
		private static int DefaultTimeout = 2000;
		private static int IsoHSize = 7; // TPKT+COTP Header Size

		// Properties
		private int _PDULength = 0;
		private int _PduSizeRequested = 480;
		private int _PLCPort = ISOTCP;
		private int _RecvTimeout = DefaultTimeout;
		private int _SendTimeout = DefaultTimeout;
		private int _ConnTimeout = DefaultTimeout;

		// Privates
		private string IPAddress;
		private byte LocalTSAP_HI;
		private byte LocalTSAP_LO;
		private byte RemoteTSAP_HI;
		private byte RemoteTSAP_LO;
		private byte LastPDUType;
		private ushort ConnType = CONNTYPE_PG;
		private byte[] PDU = new byte[2048];
		private MsgSocket Socket = null;
		private int Time_ms = 0;

		private void CreateSocket()
		{
			try
			{
				Socket = new MsgSocket();
				Socket.ConnectTimeout = _ConnTimeout;
				Socket.ReadTimeout = _RecvTimeout;
				Socket.WriteTimeout = _SendTimeout;
			}
			catch
			{
			}
		}

		private int TCPConnect()
		{
			if (_LastError == 0)
				try
				{
					_LastError = Socket.Connect(IPAddress, _PLCPort);
				}
				catch
				{
					_LastError = S7Consts.errTCPConnectionFailed;
				}
			return _LastError;
		}

		private void RecvPacket(byte[] Buffer, int Start, int Size)
		{
			if (Connected)
				_LastError = Socket.Receive(Buffer, Start, Size);
			else
				_LastError = S7Consts.errTCPNotConnected;
		}

		private void SendPacket(byte[] Buffer, int Len)
		{
			_LastError = Socket.Send(Buffer, Len);
		}

		private void SendPacket(byte[] Buffer)
		{
			if (Connected)
				SendPacket(Buffer, Buffer.Length);
			else
				_LastError = S7Consts.errTCPNotConnected;
		}

		private int RecvIsoPacket()
		{
			Boolean Done = false;
			int Size = 0;
			while ((_LastError == 0) && !Done)
			{
				// Get TPKT (4 bytes)
				RecvPacket(PDU, 0, 4);
				if (_LastError == 0)
				{
					Size = S7.GetWordAt(PDU, 2);
					// Check 0 bytes Data Packet (only TPKT+COTP = 7 bytes)
					if (Size == IsoHSize)
						RecvPacket(PDU, 4, 3); // Skip remaining 3 bytes and Done is still false
					else
					{
						if ((Size > _PduSizeRequested + IsoHSize) || (Size < MinPduSize))
							_LastError = S7Consts.errIsoInvalidPDU;
						else
							Done = true; // a valid Length !=7 && >16 && <247
					}
				}
			}
			if (_LastError == 0)
			{
				RecvPacket(PDU, 4, 3); // Skip remaining 3 COTP bytes
				LastPDUType = PDU[5];   // Stores PDU Type, we need it 
										// Receives the S7 Payload          
				RecvPacket(PDU, 7, Size - IsoHSize);
			}
			if (_LastError == 0)
				return Size;
			else
				return 0;
		}

		private int ISOConnect()
		{
			int Size;
			ISO_CR[16] = LocalTSAP_HI;
			ISO_CR[17] = LocalTSAP_LO;
			ISO_CR[20] = RemoteTSAP_HI;
			ISO_CR[21] = RemoteTSAP_LO;

			// Sends the connection request telegram      
			SendPacket(ISO_CR);
			if (_LastError == 0)
			{
				// Gets the reply (if any)
				Size = RecvIsoPacket();
				if (_LastError == 0)
				{
					if (Size == 22)
					{
						if (LastPDUType != (byte)0xD0) // 0xD0 = CC Connection confirm
							_LastError = S7Consts.errIsoConnect;
					}
					else
						_LastError = S7Consts.errIsoInvalidPDU;
				}
			}
			return _LastError;
		}

		private int NegotiatePduLength()
		{
			int Length;
			// Set PDU Size Requested
			S7.SetWordAt(S7_PN, 23, (ushort)_PduSizeRequested);
			// Sends the connection request telegram
			SendPacket(S7_PN);
			if (_LastError == 0)
			{
				Length = RecvIsoPacket();
				if (_LastError == 0)
				{
					// check S7 Error
					if ((Length == 27) && (PDU[17] == 0) && (PDU[18] == 0))  // 20 = size of Negotiate Answer
					{
						// Get PDU Size Negotiated
						_PDULength = S7.GetWordAt(PDU, 25);
						if (_PDULength <= 0)
							_LastError = S7Consts.errCliNegotiatingPDU;
					}
					else
						_LastError = S7Consts.errCliNegotiatingPDU;
				}
			}
			return _LastError;
		}

		private int CpuError(ushort Error)
		{
			switch (Error)
			{
				case 0: return 0;
				case Code7AddressOutOfRange: return S7Consts.errCliAddressOutOfRange;
				case Code7InvalidTransportSize: return S7Consts.errCliInvalidTransportSize;
				case Code7WriteDataSizeMismatch: return S7Consts.errCliWriteDataSizeMismatch;
				case Code7ResItemNotAvailable:
				case Code7ResItemNotAvailable1: return S7Consts.errCliItemNotAvailable;
				case Code7DataOverPDU: return S7Consts.errCliSizeOverPDU;
				case Code7InvalidValue: return S7Consts.errCliInvalidValue;
				case Code7FunNotAvailable: return S7Consts.errCliFunNotAvailable;
				case Code7NeedPassword: return S7Consts.errCliNeedPassword;
				case Code7InvalidPassword: return S7Consts.errCliInvalidPassword;
				case Code7NoPasswordToSet:
				case Code7NoPasswordToClear: return S7Consts.errCliNoPasswordToSetOrClear;
				default:
					return S7Consts.errCliFunctionRefused;
			};
		}

		#endregion

		#region [Class Control]

		public S7Client()
		{
			CreateSocket();
		}

		~S7Client()
		{
			Disconnect();
		}

		public int Connect()
		{
			_LastError = 0;
			Time_ms = 0;
			int Elapsed = Environment.TickCount;
			if (!Connected)
			{
				TCPConnect(); // First stage : TCP Connection
				if (_LastError == 0)
				{
					ISOConnect(); // Second stage : ISOTCP (ISO 8073) Connection
					if (_LastError == 0)
					{
						_LastError = NegotiatePduLength(); // Third stage : S7 PDU negotiation
					}
				}
			}
			if (_LastError != 0)
				Disconnect();
			else
				Time_ms = Environment.TickCount - Elapsed;

			return _LastError;
		}

		public int ConnectTo(string Address, int Rack, int Slot)
		{
			UInt16 RemoteTSAP = (UInt16)((ConnType << 8) + (Rack * 0x20) + Slot);
			SetConnectionParams(Address, 0x0100, RemoteTSAP);
			return Connect();
		}

		public int SetConnectionParams(string Address, ushort LocalTSAP, ushort RemoteTSAP)
		{
			int LocTSAP = LocalTSAP & 0x0000FFFF;
			int RemTSAP = RemoteTSAP & 0x0000FFFF;
			IPAddress = Address;
			LocalTSAP_HI = (byte)(LocTSAP >> 8);
			LocalTSAP_LO = (byte)(LocTSAP & 0x00FF);
			RemoteTSAP_HI = (byte)(RemTSAP >> 8);
			RemoteTSAP_LO = (byte)(RemTSAP & 0x00FF);
			return 0;
		}

		public int SetConnectionType(ushort ConnectionType)
		{
			ConnType = ConnectionType;
			return 0;
		}

		public int Disconnect()
		{
			Socket.Close();
			return 0;
		}

		public int GetParam(Int32 ParamNumber, ref int Value)
		{
			int Result = 0;
			switch (ParamNumber)
			{
				case S7Consts.p_u16_RemotePort:
					{
						Value = PLCPort;
						break;
					}
				case S7Consts.p_i32_PingTimeout:
					{
						Value = ConnTimeout;
						break;
					}
				case S7Consts.p_i32_SendTimeout:
					{
						Value = SendTimeout;
						break;
					}
				case S7Consts.p_i32_RecvTimeout:
					{
						Value = RecvTimeout;
						break;
					}
				case S7Consts.p_i32_PDURequest:
					{
						Value = PduSizeRequested;
						break;
					}
				default:
					{
						Result = S7Consts.errCliInvalidParamNumber;
						break;
					}
			}
			return Result;
		}

		// Set Properties for compatibility with Snap7.net.cs
		public int SetParam(Int32 ParamNumber, ref int Value)
		{
			int Result = 0;
			switch (ParamNumber)
			{
				case S7Consts.p_u16_RemotePort:
					{
						PLCPort = Value;
						break;
					}
				case S7Consts.p_i32_PingTimeout:
					{
						ConnTimeout = Value;
						break;
					}
				case S7Consts.p_i32_SendTimeout:
					{
						SendTimeout = Value;
						break;
					}
				case S7Consts.p_i32_RecvTimeout:
					{
						RecvTimeout = Value;
						break;
					}
				case S7Consts.p_i32_PDURequest:
					{
						PduSizeRequested = Value;
						break;
					}
				default:
					{
						Result = S7Consts.errCliInvalidParamNumber;
						break;
					}
			}
			return Result;
		}

		public delegate void S7CliCompletion(IntPtr usrPtr, int opCode, int opResult);
		public int SetAsCallBack(S7CliCompletion Completion, IntPtr usrPtr)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		#endregion

		#region [Data I/O main functions]

		public int ReadArea(int Area, int DBNumber, int Start, int Amount, int WordLen, byte[] Buffer)
		{
			int BytesRead = 0;
			return ReadArea(Area, DBNumber, Start, Amount, WordLen, Buffer, ref BytesRead);
		}

		public int ReadArea(int Area, int DBNumber, int Start, int Amount, int WordLen, byte[] Buffer, ref int BytesRead)
		{
			int Address;
			int NumElements;
			int MaxElements;
			int TotElements;
			int SizeRequested;
			int Length;
			int Offset = 0;
			int WordSize = 1;

			_LastError = 0;
			Time_ms = 0;
			int Elapsed = Environment.TickCount;
			// Some adjustment
			if (Area == S7Consts.S7AreaCT)
				WordLen = S7Consts.S7WLCounter;
			if (Area == S7Consts.S7AreaTM)
				WordLen = S7Consts.S7WLTimer;

			// Calc Word size          
			WordSize = S7.DataSizeByte(WordLen);
			if (WordSize == 0)
				return S7Consts.errCliInvalidWordLen;

			if (WordLen == S7Consts.S7WLBit)
				Amount = 1;  // Only 1 bit can be transferred at time
			else
			{
				if ((WordLen != S7Consts.S7WLCounter) && (WordLen != S7Consts.S7WLTimer))
				{
					Amount = Amount * WordSize;
					WordSize = 1;
					WordLen = S7Consts.S7WLByte;
				}
			}

			MaxElements = (_PDULength - 18) / WordSize; // 18 = Reply telegram header
			TotElements = Amount;

			while ((TotElements > 0) && (_LastError == 0))
			{
				NumElements = TotElements;
				if (NumElements > MaxElements)
					NumElements = MaxElements;

				SizeRequested = NumElements * WordSize;

				// Setup the telegram
				Array.Copy(S7_RW, 0, PDU, 0, Size_RD);
				// Set DB Number
				PDU[27] = (byte)Area;
				// Set Area
				if (Area == S7Consts.S7AreaDB)
					S7.SetWordAt(PDU, 25, (ushort)DBNumber);

				// Adjusts Start and word length
				if ((WordLen == S7Consts.S7WLBit) || (WordLen == S7Consts.S7WLCounter) || (WordLen == S7Consts.S7WLTimer))
				{
					Address = Start;
					PDU[22] = (byte)WordLen;
				}
				else
					Address = Start << 3;

				// Num elements
				S7.SetWordAt(PDU, 23, (ushort)NumElements);

				// Address into the PLC (only 3 bytes)           
				PDU[30] = (byte)(Address & 0x0FF);
				Address = Address >> 8;
				PDU[29] = (byte)(Address & 0x0FF);
				Address = Address >> 8;
				PDU[28] = (byte)(Address & 0x0FF);

				SendPacket(PDU, Size_RD);
				if (_LastError == 0)
				{
					Length = RecvIsoPacket();
					if (_LastError == 0)
					{
						if (Length < 25)
							_LastError = S7Consts.errIsoInvalidDataSize;
						else
						{
							if (PDU[21] != 0xFF)
								_LastError = CpuError(PDU[21]);
							else
							{
								Array.Copy(PDU, 25, Buffer, Offset, SizeRequested);
								Offset += SizeRequested;
							}
						}
					}
				}
				TotElements -= NumElements;
				Start += NumElements * WordSize;
			}

			if (_LastError == 0)
			{
				BytesRead = Offset;
				Time_ms = Environment.TickCount - Elapsed;
			}
			else
				BytesRead = 0;
			return _LastError;
		}

		public int WriteArea(int Area, int DBNumber, int Start, int Amount, int WordLen, byte[] Buffer)
		{
			int BytesWritten = 0;
			return WriteArea(Area, DBNumber, Start, Amount, WordLen, Buffer, ref BytesWritten);
		}

		public int WriteArea(int Area, int DBNumber, int Start, int Amount, int WordLen, byte[] Buffer, ref int BytesWritten)
		{
			int Address;
			int NumElements;
			int MaxElements;
			int TotElements;
			int DataSize;
			int IsoSize;
			int Length;
			int Offset = 0;
			int WordSize = 1;

			_LastError = 0;
			Time_ms = 0;
			int Elapsed = Environment.TickCount;
			// Some adjustment
			if (Area == S7Consts.S7AreaCT)
				WordLen = S7Consts.S7WLCounter;
			if (Area == S7Consts.S7AreaTM)
				WordLen = S7Consts.S7WLTimer;

			// Calc Word size          
			WordSize = S7.DataSizeByte(WordLen);
			if (WordSize == 0)
				return S7Consts.errCliInvalidWordLen;

			if (WordLen == S7Consts.S7WLBit) // Only 1 bit can be transferred at time
				Amount = 1;
			else
			{
				if ((WordLen != S7Consts.S7WLCounter) && (WordLen != S7Consts.S7WLTimer))
				{
					Amount = Amount * WordSize;
					WordSize = 1;
					WordLen = S7Consts.S7WLByte;
				}
			}

			MaxElements = (_PDULength - 35) / WordSize; // 35 = Reply telegram header
			TotElements = Amount;

			while ((TotElements > 0) && (_LastError == 0))
			{
				NumElements = TotElements;
				if (NumElements > MaxElements)
					NumElements = MaxElements;

				DataSize = NumElements * WordSize;
				IsoSize = Size_WR + DataSize;

				// Setup the telegram
				Array.Copy(S7_RW, 0, PDU, 0, Size_WR);
				// Whole telegram Size
				S7.SetWordAt(PDU, 2, (ushort)IsoSize);
				// Data Length
				Length = DataSize + 4;
				S7.SetWordAt(PDU, 15, (ushort)Length);
				// Function
				PDU[17] = (byte)0x05;
				// Set DB Number
				PDU[27] = (byte)Area;
				if (Area == S7Consts.S7AreaDB)
					S7.SetWordAt(PDU, 25, (ushort)DBNumber);


				// Adjusts Start and word length
				if ((WordLen == S7Consts.S7WLBit) || (WordLen == S7Consts.S7WLCounter) || (WordLen == S7Consts.S7WLTimer))
				{
					Address = Start;
					Length = DataSize;
					PDU[22] = (byte)WordLen;
				}
				else
				{
					Address = Start << 3;
					Length = DataSize << 3;
				}

				// Num elements
				S7.SetWordAt(PDU, 23, (ushort)NumElements);
				// Address into the PLC
				PDU[30] = (byte)(Address & 0x0FF);
				Address = Address >> 8;
				PDU[29] = (byte)(Address & 0x0FF);
				Address = Address >> 8;
				PDU[28] = (byte)(Address & 0x0FF);

				// Transport Size
				switch (WordLen)
				{
					case S7Consts.S7WLBit:
						PDU[32] = TS_ResBit;
						break;
					case S7Consts.S7WLCounter:
					case S7Consts.S7WLTimer:
						PDU[32] = TS_ResOctet;
						break;
					default:
						PDU[32] = TS_ResByte; // byte/word/dword etc.
						break;
				};
				// Length
				S7.SetWordAt(PDU, 33, (ushort)Length);

				// Copies the Data
				Array.Copy(Buffer, Offset, PDU, 35, DataSize);

				SendPacket(PDU, IsoSize);
				if (_LastError == 0)
				{
					Length = RecvIsoPacket();
					if (_LastError == 0)
					{
						if (Length == 22)
						{
							if (PDU[21] != (byte)0xFF)
								_LastError = CpuError(PDU[21]);
						}
						else
							_LastError = S7Consts.errIsoInvalidPDU;
					}
				}
				Offset += DataSize;
				TotElements -= NumElements;
				Start += NumElements * WordSize;
			}

			if (_LastError == 0)
			{
				BytesWritten = Offset;
				Time_ms = Environment.TickCount - Elapsed;
			}
			else
				BytesWritten = 0;

			return _LastError;
		}

		public int ReadMultiVars(S7DataItem[] Items, int ItemsCount)
		{
			int Offset;
			int Length;
			int ItemSize;
			byte[] S7Item = new byte[12];
			byte[] S7ItemRead = new byte[1024];

			_LastError = 0;
			Time_ms = 0;
			int Elapsed = Environment.TickCount;

			// Checks items
			if (ItemsCount > MaxVars)
				return S7Consts.errCliTooManyItems;

			// Fills Header
			Array.Copy(S7_MRD_HEADER, 0, PDU, 0, S7_MRD_HEADER.Length);
			S7.SetWordAt(PDU, 13, (ushort)(ItemsCount * S7Item.Length + 2));
			PDU[18] = (byte)ItemsCount;
			// Fills the Items
			Offset = 19;
			for (int c = 0; c < ItemsCount; c++)
			{
				Array.Copy(S7_MRD_ITEM, S7Item, S7Item.Length);
				S7Item[3] = (byte)Items[c].WordLen;
				S7.SetWordAt(S7Item, 4, (ushort)Items[c].Amount);
				if (Items[c].Area == S7Consts.S7AreaDB)
					S7.SetWordAt(S7Item, 6, (ushort)Items[c].DBNumber);
				S7Item[8] = (byte)Items[c].Area;

				// Address into the PLC
				int Address = Items[c].Start;
				S7Item[11] = (byte)(Address & 0x0FF);
				Address = Address >> 8;
				S7Item[10] = (byte)(Address & 0x0FF);
				Address = Address >> 8;
				S7Item[09] = (byte)(Address & 0x0FF);

				Array.Copy(S7Item, 0, PDU, Offset, S7Item.Length);
				Offset += S7Item.Length;
			}

			if (Offset > _PDULength)
				return S7Consts.errCliSizeOverPDU;

			S7.SetWordAt(PDU, 2, (ushort)Offset); // Whole size
			SendPacket(PDU, Offset);

			if (_LastError != 0)
				return _LastError;
			// Get Answer
			Length = RecvIsoPacket();
			if (_LastError != 0)
				return _LastError;
			// Check ISO Length
			if (Length < 22)
			{
				_LastError = S7Consts.errIsoInvalidPDU; // PDU too Small
				return _LastError;
			}
			// Check Global Operation Result
			_LastError = CpuError(S7.GetWordAt(PDU, 17));
			if (_LastError != 0)
				return _LastError;
			// Get true ItemsCount
			int ItemsRead = S7.GetByteAt(PDU, 20);
			if ((ItemsRead != ItemsCount) || (ItemsRead > MaxVars))
			{
				_LastError = S7Consts.errCliInvalidPlcAnswer;
				return _LastError;
			}
			// Get Data
			Offset = 21;
			for (int c = 0; c < ItemsCount; c++)
			{
				// Get the Item
				Array.Copy(PDU, Offset, S7ItemRead, 0, Length - Offset);
				if (S7ItemRead[0] == 0xff)
				{
					ItemSize = (int)S7.GetWordAt(S7ItemRead, 2);
					if ((S7ItemRead[1] != TS_ResOctet) && (S7ItemRead[1] != TS_ResReal) && (S7ItemRead[1] != TS_ResBit))
						ItemSize = ItemSize >> 3;
					Marshal.Copy(S7ItemRead, 4, Items[c].pData, ItemSize);
					Items[c].Result = 0;
					if (ItemSize % 2 != 0)
						ItemSize++; // Odd size are rounded
					Offset = Offset + 4 + ItemSize;
				}
				else
				{
					Items[c].Result = CpuError(S7ItemRead[0]);
					Offset += 4; // Skip the Item header                           
				}
			}
			Time_ms = Environment.TickCount - Elapsed;
			return _LastError;
		}

		public int WriteMultiVars(S7DataItem[] Items, int ItemsCount)
		{
			int Offset;
			int ParLength;
			int DataLength;
			int ItemDataSize;
			byte[] S7ParItem = new byte[S7_MWR_PARAM.Length];
			byte[] S7DataItem = new byte[1024];

			_LastError = 0;
			Time_ms = 0;
			int Elapsed = Environment.TickCount;

			// Checks items
			if (ItemsCount > MaxVars)
				return S7Consts.errCliTooManyItems;
			// Fills Header
			Array.Copy(S7_MWR_HEADER, 0, PDU, 0, S7_MWR_HEADER.Length);
			ParLength = ItemsCount * S7_MWR_PARAM.Length + 2;
			S7.SetWordAt(PDU, 13, (ushort)ParLength);
			PDU[18] = (byte)ItemsCount;
			// Fills Params
			Offset = S7_MWR_HEADER.Length;
			for (int c = 0; c < ItemsCount; c++)
			{
				Array.Copy(S7_MWR_PARAM, 0, S7ParItem, 0, S7_MWR_PARAM.Length);
				S7ParItem[3] = (byte)Items[c].WordLen;
				S7ParItem[8] = (byte)Items[c].Area;
				S7.SetWordAt(S7ParItem, 4, (ushort)Items[c].Amount);
				S7.SetWordAt(S7ParItem, 6, (ushort)Items[c].DBNumber);
				// Address into the PLC
				int Address = Items[c].Start;
				S7ParItem[11] = (byte)(Address & 0x0FF);
				Address = Address >> 8;
				S7ParItem[10] = (byte)(Address & 0x0FF);
				Address = Address >> 8;
				S7ParItem[09] = (byte)(Address & 0x0FF);
				Array.Copy(S7ParItem, 0, PDU, Offset, S7ParItem.Length);
				Offset += S7_MWR_PARAM.Length;
			}
			// Fills Data
			DataLength = 0;
			for (int c = 0; c < ItemsCount; c++)
			{
				S7DataItem[0] = 0x00;
				switch (Items[c].WordLen)
				{
					case S7Consts.S7WLBit:
						S7DataItem[1] = TS_ResBit;
						break;
					case S7Consts.S7WLCounter:
					case S7Consts.S7WLTimer:
						S7DataItem[1] = TS_ResOctet;
						break;
					default:
						S7DataItem[1] = TS_ResByte; // byte/word/dword etc.
						break;
				};
				if ((Items[c].WordLen == S7Consts.S7WLTimer) || (Items[c].WordLen == S7Consts.S7WLCounter))
					ItemDataSize = Items[c].Amount * 2;
				else
					ItemDataSize = Items[c].Amount;

				if ((S7DataItem[1] != TS_ResOctet) && (S7DataItem[1] != TS_ResBit))
					S7.SetWordAt(S7DataItem, 2, (ushort)(ItemDataSize * 8));
				else
					S7.SetWordAt(S7DataItem, 2, (ushort)ItemDataSize);

				Marshal.Copy(Items[c].pData, S7DataItem, 4, ItemDataSize);
				if (ItemDataSize % 2 != 0)
				{
					S7DataItem[ItemDataSize + 4] = 0x00;
					ItemDataSize++;
				}
				Array.Copy(S7DataItem, 0, PDU, Offset, ItemDataSize + 4);
				Offset = Offset + ItemDataSize + 4;
				DataLength = DataLength + ItemDataSize + 4;
			}

			// Checks the size
			if (Offset > _PDULength)
				return S7Consts.errCliSizeOverPDU;

			S7.SetWordAt(PDU, 2, (ushort)Offset); // Whole size
			S7.SetWordAt(PDU, 15, (ushort)DataLength); // Whole size
			SendPacket(PDU, Offset);

			RecvIsoPacket();
			if (_LastError == 0)
			{
				// Check Global Operation Result
				_LastError = CpuError(S7.GetWordAt(PDU, 17));
				if (_LastError != 0)
					return _LastError;
				// Get true ItemsCount
				int ItemsWritten = S7.GetByteAt(PDU, 20);
				if ((ItemsWritten != ItemsCount) || (ItemsWritten > MaxVars))
				{
					_LastError = S7Consts.errCliInvalidPlcAnswer;
					return _LastError;
				}

				for (int c = 0; c < ItemsCount; c++)
				{
					if (PDU[c + 21] == 0xFF)
						Items[c].Result = 0;
					else
						Items[c].Result = CpuError((ushort)PDU[c + 21]);
				}
				Time_ms = Environment.TickCount - Elapsed;
			}
			return _LastError;
		}

		#endregion

		#region [Data I/O lean functions]

		public int DBRead(int DBNumber, int Start, int Size, byte[] Buffer)
		{
			return ReadArea(S7Consts.S7AreaDB, DBNumber, Start, Size, S7Consts.S7WLByte, Buffer);
		}

		public int DBWrite(int DBNumber, int Start, int Size, byte[] Buffer)
		{
			return WriteArea(S7Consts.S7AreaDB, DBNumber, Start, Size, S7Consts.S7WLByte, Buffer);
		}

		public int MBRead(int Start, int Size, byte[] Buffer)
		{
			return ReadArea(S7Consts.S7AreaMK, 0, Start, Size, S7Consts.S7WLByte, Buffer);
		}

		public int MBWrite(int Start, int Size, byte[] Buffer)
		{
			return WriteArea(S7Consts.S7AreaMK, 0, Start, Size, S7Consts.S7WLByte, Buffer);
		}

		public int EBRead(int Start, int Size, byte[] Buffer)
		{
			return ReadArea(S7Consts.S7AreaPE, 0, Start, Size, S7Consts.S7WLByte, Buffer);
		}

		public int EBWrite(int Start, int Size, byte[] Buffer)
		{
			return WriteArea(S7Consts.S7AreaPE, 0, Start, Size, S7Consts.S7WLByte, Buffer);
		}

		public int ABRead(int Start, int Size, byte[] Buffer)
		{
			return ReadArea(S7Consts.S7AreaPA, 0, Start, Size, S7Consts.S7WLByte, Buffer);
		}

		public int ABWrite(int Start, int Size, byte[] Buffer)
		{
			return WriteArea(S7Consts.S7AreaPA, 0, Start, Size, S7Consts.S7WLByte, Buffer);
		}

		public int TMRead(int Start, int Amount, ushort[] Buffer)
		{
			byte[] sBuffer = new byte[Amount * 2];
			int Result = ReadArea(S7Consts.S7AreaTM, 0, Start, Amount, S7Consts.S7WLTimer, sBuffer);
			if (Result == 0)
			{
				for (int c = 0; c < Amount; c++)
				{
					Buffer[c] = (ushort)((sBuffer[c * 2 + 1] << 8) + (sBuffer[c * 2]));
				}
			}
			return Result;
		}

		public int TMWrite(int Start, int Amount, ushort[] Buffer)
		{
			byte[] sBuffer = new byte[Amount * 2];
			for (int c = 0; c < Amount; c++)
			{
				sBuffer[c * 2 + 1] = (byte)((Buffer[c] & 0xFF00) >> 8);
				sBuffer[c * 2] = (byte)(Buffer[c] & 0x00FF);
			}
			return WriteArea(S7Consts.S7AreaTM, 0, Start, Amount, S7Consts.S7WLTimer, sBuffer);
		}

		public int CTRead(int Start, int Amount, ushort[] Buffer)
		{
			byte[] sBuffer = new byte[Amount * 2];
			int Result = ReadArea(S7Consts.S7AreaCT, 0, Start, Amount, S7Consts.S7WLCounter, sBuffer);
			if (Result == 0)
			{
				for (int c = 0; c < Amount; c++)
				{
					Buffer[c] = (ushort)((sBuffer[c * 2 + 1] << 8) + (sBuffer[c * 2]));
				}
			}
			return Result;
		}

		public int CTWrite(int Start, int Amount, ushort[] Buffer)
		{
			byte[] sBuffer = new byte[Amount * 2];
			for (int c = 0; c < Amount; c++)
			{
				sBuffer[c * 2 + 1] = (byte)((Buffer[c] & 0xFF00) >> 8);
				sBuffer[c * 2] = (byte)(Buffer[c] & 0x00FF);
			}
			return WriteArea(S7Consts.S7AreaCT, 0, Start, Amount, S7Consts.S7WLCounter, sBuffer);
		}

		#endregion

		#region [Directory functions]

		public int ListBlocks(ref S7BlocksList List)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		private string SiemensTimestamp(long EncodedDate)
		{
			DateTime DT = new DateTime(1984, 1, 1).AddSeconds(EncodedDate * 86400);
#if WINDOWS_UWP || NETFX_CORE
            return DT.ToString(System.Globalization.DateTimeFormatInfo.CurrentInfo.ShortDatePattern);
#else
			return DT.ToShortDateString();
#endif
		}

		public int GetAgBlockInfo(int BlockType, int BlockNum, ref S7BlockInfo Info)
		{
			_LastError = 0;
			Time_ms = 0;
			int Elapsed = Environment.TickCount;

			S7_BI[30] = (byte)BlockType;
			// Block Number
			S7_BI[31] = (byte)((BlockNum / 10000) + 0x30);
			BlockNum = BlockNum % 10000;
			S7_BI[32] = (byte)((BlockNum / 1000) + 0x30);
			BlockNum = BlockNum % 1000;
			S7_BI[33] = (byte)((BlockNum / 100) + 0x30);
			BlockNum = BlockNum % 100;
			S7_BI[34] = (byte)((BlockNum / 10) + 0x30);
			BlockNum = BlockNum % 10;
			S7_BI[35] = (byte)((BlockNum / 1) + 0x30);

			SendPacket(S7_BI);

			if (_LastError == 0)
			{
				int Length = RecvIsoPacket();
				if (Length > 32) // the minimum expected
				{
					ushort Result = S7.GetWordAt(PDU, 27);
					if (Result == 0)
					{
						Info.BlkFlags = PDU[42];
						Info.BlkLang = PDU[43];
						Info.BlkType = PDU[44];
						Info.BlkNumber = S7.GetWordAt(PDU, 45);
						Info.LoadSize = S7.GetDIntAt(PDU, 47);
						Info.CodeDate = SiemensTimestamp(S7.GetWordAt(PDU, 59));
						Info.IntfDate = SiemensTimestamp(S7.GetWordAt(PDU, 65));
						Info.SBBLength = S7.GetWordAt(PDU, 67);
						Info.LocalData = S7.GetWordAt(PDU, 71);
						Info.MC7Size = S7.GetWordAt(PDU, 73);
						Info.Author = S7.GetCharsAt(PDU, 75, 8).Trim(new char[] { (char)0 });
						Info.Family = S7.GetCharsAt(PDU, 83, 8).Trim(new char[] { (char)0 });
						Info.Header = S7.GetCharsAt(PDU, 91, 8).Trim(new char[] { (char)0 });
						Info.Version = PDU[99];
						Info.CheckSum = S7.GetWordAt(PDU, 101);
					}
					else
						_LastError = CpuError(Result);
				}
				else
					_LastError = S7Consts.errIsoInvalidPDU;
			}
			if (_LastError == 0)
				Time_ms = Environment.TickCount - Elapsed;

			return _LastError;

		}

		public int GetPgBlockInfo(ref S7BlockInfo Info, byte[] Buffer, int Size)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int ListBlocksOfType(int BlockType, ushort[] List, ref int ItemsCount)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		#endregion

		#region [Blocks functions]

		public int Upload(int BlockType, int BlockNum, byte[] UsrData, ref int Size)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int FullUpload(int BlockType, int BlockNum, byte[] UsrData, ref int Size)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int Download(int BlockNum, byte[] UsrData, int Size)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int Delete(int BlockType, int BlockNum)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int DBGet(int DBNumber, byte[] UsrData, ref int Size)
		{
			S7BlockInfo BI = new S7BlockInfo();
			int Elapsed = Environment.TickCount;
			Time_ms = 0;

			_LastError = GetAgBlockInfo(Block_DB, DBNumber, ref BI);

			if (_LastError == 0)
			{
				int DBSize = BI.MC7Size;
				if (DBSize <= UsrData.Length)
				{
					Size = DBSize;
					_LastError = DBRead(DBNumber, 0, DBSize, UsrData);
					if (_LastError == 0)
						Size = DBSize;
				}
				else
					_LastError = S7Consts.errCliBufferTooSmall;
			}
			if (_LastError == 0)
				Time_ms = Environment.TickCount - Elapsed;
			return _LastError;
		}

		public int DBFill(int DBNumber, int FillChar)
		{
			S7BlockInfo BI = new S7BlockInfo();
			int Elapsed = Environment.TickCount;
			Time_ms = 0;

			_LastError = GetAgBlockInfo(Block_DB, DBNumber, ref BI);

			if (_LastError == 0)
			{
				byte[] Buffer = new byte[BI.MC7Size];
				for (int c = 0; c < BI.MC7Size; c++)
					Buffer[c] = (byte)FillChar;
				_LastError = DBWrite(DBNumber, 0, BI.MC7Size, Buffer);
			}
			if (_LastError == 0)
				Time_ms = Environment.TickCount - Elapsed;
			return _LastError;
		}

		#endregion

		#region [Date/Time functions]

		public int GetPlcDateTime(ref DateTime DT)
		{
			int Length;
			_LastError = 0;
			Time_ms = 0;
			int Elapsed = Environment.TickCount;

			SendPacket(S7_GET_DT);
			if (_LastError == 0)
			{
				Length = RecvIsoPacket();
				if (Length > 30) // the minimum expected
				{
					if ((S7.GetWordAt(PDU, 27) == 0) && (PDU[29] == 0xFF))
					{
						DT = S7.GetDateTimeAt(PDU, 35);
					}
					else
						_LastError = S7Consts.errCliInvalidPlcAnswer;
				}
				else
					_LastError = S7Consts.errIsoInvalidPDU;
			}

			if (_LastError == 0)
				Time_ms = Environment.TickCount - Elapsed;

			return _LastError;
		}

		public int SetPlcDateTime(DateTime DT)
		{
			int Length;
			_LastError = 0;
			Time_ms = 0;
			int Elapsed = Environment.TickCount;

			S7.SetDateTimeAt(S7_SET_DT, 31, DT);
			SendPacket(S7_SET_DT);
			if (_LastError == 0)
			{
				Length = RecvIsoPacket();
				if (Length > 30) // the minimum expected
				{
					if (S7.GetWordAt(PDU, 27) != 0)
						_LastError = S7Consts.errCliInvalidPlcAnswer;
				}
				else
					_LastError = S7Consts.errIsoInvalidPDU;
			}
			if (_LastError == 0)
				Time_ms = Environment.TickCount - Elapsed;

			return _LastError;
		}

		public int SetPlcSystemDateTime()
		{
			return SetPlcDateTime(DateTime.Now);
		}

		#endregion

		#region [System Info functions]

		public int GetOrderCode(ref S7OrderCode Info)
		{
			S7SZL SZL = new S7SZL();
			int Size = 1024;
			SZL.Data = new byte[Size];
			int Elapsed = Environment.TickCount;
			_LastError = ReadSZL(0x0011, 0x000, ref SZL, ref Size);
			if (_LastError == 0)
			{
				Info.Code = S7.GetCharsAt(SZL.Data, 2, 20);
				Info.V1 = SZL.Data[Size - 3];
				Info.V2 = SZL.Data[Size - 2];
				Info.V3 = SZL.Data[Size - 1];
			}
			if (_LastError == 0)
				Time_ms = Environment.TickCount - Elapsed;
			return _LastError;
		}

		public int GetCpuInfo(ref S7CpuInfo Info)
		{
			S7SZL SZL = new S7SZL();
			int Size = 1024;
			SZL.Data = new byte[Size];
			int Elapsed = Environment.TickCount;
			_LastError = ReadSZL(0x001C, 0x000, ref SZL, ref Size);
			if (_LastError == 0)
			{
				Info.ModuleTypeName = S7.GetCharsAt(SZL.Data, 172, 32);
				Info.SerialNumber = S7.GetCharsAt(SZL.Data, 138, 24);
				Info.ASName = S7.GetCharsAt(SZL.Data, 2, 24);
				Info.Copyright = S7.GetCharsAt(SZL.Data, 104, 26);
				Info.ModuleName = S7.GetCharsAt(SZL.Data, 36, 24);
			}
			if (_LastError == 0)
				Time_ms = Environment.TickCount - Elapsed;
			return _LastError;
		}

		public int GetCpInfo(ref S7CpInfo Info)
		{
			S7SZL SZL = new S7SZL();
			int Size = 1024;
			SZL.Data = new byte[Size];
			int Elapsed = Environment.TickCount;
			_LastError = ReadSZL(0x0131, 0x001, ref SZL, ref Size);
			if (_LastError == 0)
			{
				Info.MaxPduLength = S7.GetIntAt(PDU, 2);
				Info.MaxConnections = S7.GetIntAt(PDU, 4);
				Info.MaxMpiRate = S7.GetDIntAt(PDU, 6);
				Info.MaxBusRate = S7.GetDIntAt(PDU, 10);
			}
			if (_LastError == 0)
				Time_ms = Environment.TickCount - Elapsed;
			return _LastError;
		}

		public int ReadSZL(int ID, int Index, ref S7SZL SZL, ref int Size)
		{
			int Length;
			int DataSZL;
			int Offset = 0;
			bool Done = false;
			bool First = true;
			byte Seq_in = 0x00;
			ushort Seq_out = 0x0000;

			_LastError = 0;
			Time_ms = 0;
			int Elapsed = Environment.TickCount;
			SZL.Header.LENTHDR = 0;

			do
			{
				if (First)
				{
					S7.SetWordAt(S7_SZL_FIRST, 11, ++Seq_out);
					S7.SetWordAt(S7_SZL_FIRST, 29, (ushort)ID);
					S7.SetWordAt(S7_SZL_FIRST, 31, (ushort)Index);
					SendPacket(S7_SZL_FIRST);
				}
				else
				{
					S7.SetWordAt(S7_SZL_NEXT, 11, ++Seq_out);
					PDU[24] = (byte)Seq_in;
					SendPacket(S7_SZL_NEXT);
				}
				if (_LastError != 0)
					return _LastError;

				Length = RecvIsoPacket();
				if (_LastError == 0)
				{
					if (First)
					{
						if (Length > 32) // the minimum expected
						{
							if ((S7.GetWordAt(PDU, 27) == 0) && (PDU[29] == (byte)0xFF))
							{
								// Gets Amount of this slice
								DataSZL = S7.GetWordAt(PDU, 31) - 8; // Skips extra params (ID, Index ...)
								Done = PDU[26] == 0x00;
								Seq_in = (byte)PDU[24]; // Slice sequence
								SZL.Header.LENTHDR = S7.GetWordAt(PDU, 37);
								SZL.Header.N_DR = S7.GetWordAt(PDU, 39);
								Array.Copy(PDU, 41, SZL.Data, Offset, DataSZL);
								//                                SZL.Copy(PDU, 41, Offset, DataSZL);
								Offset += DataSZL;
								SZL.Header.LENTHDR += SZL.Header.LENTHDR;
							}
							else
								_LastError = S7Consts.errCliInvalidPlcAnswer;
						}
						else
							_LastError = S7Consts.errIsoInvalidPDU;
					}
					else
					{
						if (Length > 32) // the minimum expected
						{
							if ((S7.GetWordAt(PDU, 27) == 0) && (PDU[29] == (byte)0xFF))
							{
								// Gets Amount of this slice
								DataSZL = S7.GetWordAt(PDU, 31);
								Done = PDU[26] == 0x00;
								Seq_in = (byte)PDU[24]; // Slice sequence
								Array.Copy(PDU, 37, SZL.Data, Offset, DataSZL);
								Offset += DataSZL;
								SZL.Header.LENTHDR += SZL.Header.LENTHDR;
							}
							else
								_LastError = S7Consts.errCliInvalidPlcAnswer;
						}
						else
							_LastError = S7Consts.errIsoInvalidPDU;
					}
				}
				First = false;
			}
			while (!Done && (_LastError == 0));
			if (_LastError == 0)
			{
				Size = SZL.Header.LENTHDR;
				Time_ms = Environment.TickCount - Elapsed;
			}
			return _LastError;
		}

		public int ReadSZLList(ref S7SZLList List, ref Int32 ItemsCount)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		#endregion

		#region [Control functions]

		public int PlcHotStart()
		{
			_LastError = 0;
			int Elapsed = Environment.TickCount;

			SendPacket(S7_HOT_START);
			if (_LastError == 0)
			{
				int Length = RecvIsoPacket();
				if (Length > 18) // 18 is the minimum expected
				{
					if (PDU[19] != pduStart)
						_LastError = S7Consts.errCliCannotStartPLC;
					else
					{
						if (PDU[20] == pduAlreadyStarted)
							_LastError = S7Consts.errCliAlreadyRun;
						else
							_LastError = S7Consts.errCliCannotStartPLC;
					}
				}
				else
					_LastError = S7Consts.errIsoInvalidPDU;
			}
			if (_LastError == 0)
				Time_ms = Environment.TickCount - Elapsed;
			return _LastError;
		}

		public int PlcColdStart()
		{
			_LastError = 0;
			int Elapsed = Environment.TickCount;

			SendPacket(S7_COLD_START);
			if (_LastError == 0)
			{
				int Length = RecvIsoPacket();
				if (Length > 18) // 18 is the minimum expected
				{
					if (PDU[19] != pduStart)
						_LastError = S7Consts.errCliCannotStartPLC;
					else
					{
						if (PDU[20] == pduAlreadyStarted)
							_LastError = S7Consts.errCliAlreadyRun;
						else
							_LastError = S7Consts.errCliCannotStartPLC;
					}
				}
				else
					_LastError = S7Consts.errIsoInvalidPDU;
			}
			if (_LastError == 0)
				Time_ms = Environment.TickCount - Elapsed;
			return _LastError;
		}

		public int PlcStop()
		{
			_LastError = 0;
			int Elapsed = Environment.TickCount;

			SendPacket(S7_STOP);
			if (_LastError == 0)
			{
				int Length = RecvIsoPacket();
				if (Length > 18) // 18 is the minimum expected
				{
					if (PDU[19] != pduStop)
						_LastError = S7Consts.errCliCannotStopPLC;
					else
					{
						if (PDU[20] == pduAlreadyStopped)
							_LastError = S7Consts.errCliAlreadyStop;
						else
							_LastError = S7Consts.errCliCannotStopPLC;
					}
				}
				else
					_LastError = S7Consts.errIsoInvalidPDU;
			}
			if (_LastError == 0)
				Time_ms = Environment.TickCount - Elapsed;
			return _LastError;
		}

		public int PlcCopyRamToRom(UInt32 Timeout)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int PlcCompress(UInt32 Timeout)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int PlcGetStatus(ref Int32 Status)
		{
			_LastError = 0;
			int Elapsed = Environment.TickCount;

			SendPacket(S7_GET_STAT);
			if (_LastError == 0)
			{
				int Length = RecvIsoPacket();
				if (Length > 30) // the minimum expected
				{
					ushort Result = S7.GetWordAt(PDU, 27);
					if (Result == 0)
					{
						switch (PDU[44])
						{
							case S7Consts.S7CpuStatusUnknown:
							case S7Consts.S7CpuStatusRun:
							case S7Consts.S7CpuStatusStop:
								{
									Status = PDU[44];
									break;
								}
							default:
								{
									// Since RUN status is always 0x08 for all CPUs and CPs, STOP status
									// sometime can be coded as 0x03 (especially for old cpu...)
									Status = S7Consts.S7CpuStatusStop;
									break;
								}
						}
					}
					else
						_LastError = CpuError(Result);
				}
				else
					_LastError = S7Consts.errIsoInvalidPDU;
			}
			if (_LastError == 0)
				Time_ms = Environment.TickCount - Elapsed;
			return _LastError;
		}

		#endregion

		#region [Security functions]
		public int SetSessionPassword(string Password)
		{
			byte[] pwd = { 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20 };
			int Length;
			_LastError = 0;
			int Elapsed = Environment.TickCount;
			// Encodes the Password
			S7.SetCharsAt(pwd, 0, Password);
			pwd[0] = (byte)(pwd[0] ^ 0x55);
			pwd[1] = (byte)(pwd[1] ^ 0x55);
			for (int c = 2; c < 8; c++)
			{
				pwd[c] = (byte)(pwd[c] ^ 0x55 ^ pwd[c - 2]);
			}
			Array.Copy(pwd, 0, S7_SET_PWD, 29, 8);
			// Sends the telegrem
			SendPacket(S7_SET_PWD);
			if (_LastError == 0)
			{
				Length = RecvIsoPacket();
				if (Length > 32) // the minimum expected
				{
					ushort Result = S7.GetWordAt(PDU, 27);
					if (Result != 0)
						_LastError = CpuError(Result);
				}
				else
					_LastError = S7Consts.errIsoInvalidPDU;
			}
			if (_LastError == 0)
				Time_ms = Environment.TickCount - Elapsed;
			return _LastError;
		}

		public int ClearSessionPassword()
		{
			int Length;
			_LastError = 0;
			int Elapsed = Environment.TickCount;
			SendPacket(S7_CLR_PWD);
			if (_LastError == 0)
			{
				Length = RecvIsoPacket();
				if (Length > 30) // the minimum expected
				{
					ushort Result = S7.GetWordAt(PDU, 27);
					if (Result != 0)
						_LastError = CpuError(Result);
				}
				else
					_LastError = S7Consts.errIsoInvalidPDU;
			}
			return _LastError;
		}

		public int GetProtection(ref S7Protection Protection)
		{
			S7Client.S7SZL SZL = new S7Client.S7SZL();
			int Size = 256;
			SZL.Data = new byte[Size];
			_LastError = ReadSZL(0x0232, 0x0004, ref SZL, ref Size);
			if (_LastError == 0)
			{
				Protection.sch_schal = S7.GetWordAt(SZL.Data, 2);
				Protection.sch_par = S7.GetWordAt(SZL.Data, 4);
				Protection.sch_rel = S7.GetWordAt(SZL.Data, 6);
				Protection.bart_sch = S7.GetWordAt(SZL.Data, 8);
				Protection.anl_sch = S7.GetWordAt(SZL.Data, 10);
			}
			return _LastError;
		}
		#endregion

		#region [Low Level]

		public int IsoExchangeBuffer(byte[] Buffer, ref Int32 Size)
		{
			_LastError = 0;
			Time_ms = 0;
			int Elapsed = Environment.TickCount;
			Array.Copy(TPKT_ISO, 0, PDU, 0, TPKT_ISO.Length);
			S7.SetWordAt(PDU, 2, (ushort)(Size + TPKT_ISO.Length));
			try
			{
				Array.Copy(Buffer, 0, PDU, TPKT_ISO.Length, Size);
			}
			catch
			{
				return S7Consts.errIsoInvalidPDU;
			}
			SendPacket(PDU, TPKT_ISO.Length + Size);
			if (_LastError == 0)
			{
				int Length = RecvIsoPacket();
				if (_LastError == 0)
				{
					Array.Copy(PDU, TPKT_ISO.Length, Buffer, 0, Length - TPKT_ISO.Length);
					Size = Length - TPKT_ISO.Length;
				}
			}
			if (_LastError == 0)
				Time_ms = Environment.TickCount - Elapsed;
			else
				Size = 0;
			return _LastError;
		}

		#endregion

		#region [Async functions (not implemented)]

		public int AsReadArea(int Area, int DBNumber, int Start, int Amount, int WordLen, byte[] Buffer)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsWriteArea(int Area, int DBNumber, int Start, int Amount, int WordLen, byte[] Buffer)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsDBRead(int DBNumber, int Start, int Size, byte[] Buffer)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsDBWrite(int DBNumber, int Start, int Size, byte[] Buffer)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsMBRead(int Start, int Size, byte[] Buffer)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsMBWrite(int Start, int Size, byte[] Buffer)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsEBRead(int Start, int Size, byte[] Buffer)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsEBWrite(int Start, int Size, byte[] Buffer)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsABRead(int Start, int Size, byte[] Buffer)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsABWrite(int Start, int Size, byte[] Buffer)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsTMRead(int Start, int Amount, ushort[] Buffer)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsTMWrite(int Start, int Amount, ushort[] Buffer)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsCTRead(int Start, int Amount, ushort[] Buffer)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsCTWrite(int Start, int Amount, ushort[] Buffer)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsListBlocksOfType(int BlockType, ushort[] List)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsReadSZL(int ID, int Index, ref S7SZL Data, ref Int32 Size)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsReadSZLList(ref S7SZLList List, ref Int32 ItemsCount)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsUpload(int BlockType, int BlockNum, byte[] UsrData, ref int Size)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsFullUpload(int BlockType, int BlockNum, byte[] UsrData, ref int Size)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int ASDownload(int BlockNum, byte[] UsrData, int Size)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsPlcCopyRamToRom(UInt32 Timeout)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsPlcCompress(UInt32 Timeout)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsDBGet(int DBNumber, byte[] UsrData, ref int Size)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public int AsDBFill(int DBNumber, int FillChar)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		public bool CheckAsCompletion(ref int opResult)
		{
			opResult = 0;
			return false;
		}

		public int WaitAsCompletion(int Timeout)
		{
			return S7Consts.errCliFunctionNotImplemented;
		}

		#endregion

		#region [Info Functions / Properties]

		public string ErrorText(int Error)
		{
			switch (Error)
			{
				case 0: return "OK";
				case S7Consts.errTCPSocketCreation: return "SYS : Error creating the Socket";
				case S7Consts.errTCPConnectionTimeout: return "TCP : Connection Timeout";
				case S7Consts.errTCPConnectionFailed: return "TCP : Connection Error";
				case S7Consts.errTCPReceiveTimeout: return "TCP : Data receive Timeout";
				case S7Consts.errTCPDataReceive: return "TCP : Error receiving Data";
				case S7Consts.errTCPSendTimeout: return "TCP : Data send Timeout";
				case S7Consts.errTCPDataSend: return "TCP : Error sending Data";
				case S7Consts.errTCPConnectionReset: return "TCP : Connection reset by the Peer";
				case S7Consts.errTCPNotConnected: return "CLI : Client not connected";
				case S7Consts.errTCPUnreachableHost: return "TCP : Unreachable host";
				case S7Consts.errIsoConnect: return "ISO : Connection Error";
				case S7Consts.errIsoInvalidPDU: return "ISO : Invalid PDU received";
				case S7Consts.errIsoInvalidDataSize: return "ISO : Invalid Buffer passed to Send/Receive";
				case S7Consts.errCliNegotiatingPDU: return "CLI : Error in PDU negotiation";
				case S7Consts.errCliInvalidParams: return "CLI : invalid param(s) supplied";
				case S7Consts.errCliJobPending: return "CLI : Job pending";
				case S7Consts.errCliTooManyItems: return "CLI : too may items (>20) in multi read/write";
				case S7Consts.errCliInvalidWordLen: return "CLI : invalid WordLength";
				case S7Consts.errCliPartialDataWritten: return "CLI : Partial data written";
				case S7Consts.errCliSizeOverPDU: return "CPU : total data exceeds the PDU size";
				case S7Consts.errCliInvalidPlcAnswer: return "CLI : invalid CPU answer";
				case S7Consts.errCliAddressOutOfRange: return "CPU : Address out of range";
				case S7Consts.errCliInvalidTransportSize: return "CPU : Invalid Transport size";
				case S7Consts.errCliWriteDataSizeMismatch: return "CPU : Data size mismatch";
				case S7Consts.errCliItemNotAvailable: return "CPU : Item not available";
				case S7Consts.errCliInvalidValue: return "CPU : Invalid value supplied";
				case S7Consts.errCliCannotStartPLC: return "CPU : Cannot start PLC";
				case S7Consts.errCliAlreadyRun: return "CPU : PLC already RUN";
				case S7Consts.errCliCannotStopPLC: return "CPU : Cannot stop PLC";
				case S7Consts.errCliCannotCopyRamToRom: return "CPU : Cannot copy RAM to ROM";
				case S7Consts.errCliCannotCompress: return "CPU : Cannot compress";
				case S7Consts.errCliAlreadyStop: return "CPU : PLC already STOP";
				case S7Consts.errCliFunNotAvailable: return "CPU : Function not available";
				case S7Consts.errCliUploadSequenceFailed: return "CPU : Upload sequence failed";
				case S7Consts.errCliInvalidDataSizeRecvd: return "CLI : Invalid data size received";
				case S7Consts.errCliInvalidBlockType: return "CLI : Invalid block type";
				case S7Consts.errCliInvalidBlockNumber: return "CLI : Invalid block number";
				case S7Consts.errCliInvalidBlockSize: return "CLI : Invalid block size";
				case S7Consts.errCliNeedPassword: return "CPU : Function not authorized for current protection level";
				case S7Consts.errCliInvalidPassword: return "CPU : Invalid password";
				case S7Consts.errCliNoPasswordToSetOrClear: return "CPU : No password to set or clear";
				case S7Consts.errCliJobTimeout: return "CLI : Job Timeout";
				case S7Consts.errCliFunctionRefused: return "CLI : function refused by CPU (Unknown error)";
				case S7Consts.errCliPartialDataRead: return "CLI : Partial data read";
				case S7Consts.errCliBufferTooSmall: return "CLI : The buffer supplied is too small to accomplish the operation";
				case S7Consts.errCliDestroying: return "CLI : Cannot perform (destroying)";
				case S7Consts.errCliInvalidParamNumber: return "CLI : Invalid Param Number";
				case S7Consts.errCliCannotChangeParam: return "CLI : Cannot change this param now";
				case S7Consts.errCliFunctionNotImplemented: return "CLI : Function not implemented";
				default: return "CLI : Unknown error (0x" + Convert.ToString(Error, 16) + ")";
			};
		}

		public int LastError()
		{
			return _LastError;
		}

		public int RequestedPduLength()
		{
			return _PduSizeRequested;
		}

		public int NegotiatedPduLength()
		{
			return _PDULength;
		}

		public int ExecTime()
		{
			return Time_ms;
		}

		public int ExecutionTime
		{
			get
			{
				return Time_ms;
			}
		}

		public int PduSizeNegotiated
		{
			get
			{
				return _PDULength;
			}
		}

		public int PduSizeRequested
		{
			get
			{
				return _PduSizeRequested;
			}
			set
			{
				if (value < MinPduSizeToRequest)
					value = MinPduSizeToRequest;
				if (value > MaxPduSizeToRequest)
					value = MaxPduSizeToRequest;
				_PduSizeRequested = value;
			}
		}

		public int PLCPort
		{
			get
			{
				return _PLCPort;
			}
			set
			{
				_PLCPort = value;
			}
		}

		public int ConnTimeout
		{
			get
			{
				return _ConnTimeout;
			}
			set
			{
				_ConnTimeout = value;
			}
		}

		public int RecvTimeout
		{
			get
			{
				return _RecvTimeout;
			}
			set
			{
				_RecvTimeout = value;
			}
		}

		public int SendTimeout
		{
			get
			{
				return _SendTimeout;
			}
			set
			{
				_SendTimeout = value;
			}
		}

		public bool Connected
		{
			get
			{
				return (Socket != null) && (Socket.Connected);
			}
		}


		#endregion
	}
}
