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Read TPKT/COTP packets / Read MaxPDU size from PLC

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Read responses from the PLS using classes for TPKT and COPT. This
makes the communication more robust. It will now handle empty COTP
packets that SoftPLS and WinAC based PLCs send out. I use RFC names for
functions and classes.

Change logic to use COTP and S7Comm reponse codes instead of
relying on packet sizes.

Read Max PDU size from connection setup. Ref #21
Change logic to use MaxPDU from cpu limit instead of hardcoded limit.

Remove var count limit.
This commit is contained in:
Thomas Jäger
2018-04-10 15:26:04 +02:00
parent 6470f8d076
commit 8a3db22629
4 changed files with 179 additions and 32 deletions
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94
S7.Net/COTP.cs Normal file
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@@ -0,0 +1,94 @@
using System;
using System.IO;
using System.Net.Sockets;
namespace S7.Net
{
/// <summary>
/// COTP Protocol functions and types
/// </summary>
internal class COTP
{
/// <summary>
/// Describes a COTP TPDU (Transport protocol data unit)
/// </summary>
public class TPDU
{
public byte HeaderLength;
public byte PDUType;
public int TPDUNumber;
public byte[] Data;
public bool LastDataUnit;
public TPDU(TPKT tPKT)
{
var br = new BinaryReader(new MemoryStream(tPKT.Data));
HeaderLength = br.ReadByte();
if (HeaderLength >= 2)
{
PDUType = br.ReadByte();
if (PDUType == 0xf0) //DT Data
{
var flags = br.ReadByte();
TPDUNumber = flags & 0x7F;
LastDataUnit = (flags & 0x80) > 0;
Data = br.ReadBytes(tPKT.Length - HeaderLength - 4); //4 = TPKT Size
return;
}
//TODO: Handle other PDUTypes
}
Data = new byte[0];
}
/// <summary>
/// Reads COTP TPDU (Transport protocol data unit) from the network stream
/// See: https://tools.ietf.org/html/rfc905
/// </summary>
/// <param name="socket">The socket to read from</param>
/// <returns>COTP DPDU instance</returns>
public static TPDU Read(Socket socket)
{
var tpkt = TPKT.Read(socket);
return new TPDU(tpkt);
}
public override string ToString()
{
return string.Format("Length: {0} PDUType: {1} TPDUNumber: {2} Last: {3} Segment Data: {4}",
HeaderLength,
PDUType,
TPDUNumber,
LastDataUnit,
BitConverter.ToString(Data)
);
}
}
/// <summary>
/// Describes a COTP TSDU (Transport service data unit). One TSDU consist of 1 ore more TPDUs
/// </summary>
public class TSDU
{
/// <summary>
/// Reads the full COTP TSDU (Transport service data unit)
/// See: https://tools.ietf.org/html/rfc905
/// </summary>
/// <returns>Data in TSDU</returns>
public static byte[] Read(Socket socket)
{
var segment = TPDU.Read(socket);
var output = new MemoryStream(segment.Data.Length);
output.Write(segment.Data, 0, segment.Data.Length);
while (!segment.LastDataUnit)
{
segment = TPDU.Read(socket);
output.Write(segment.Data, (int)output.Position, segment.Data.Length);
}
return output.GetBuffer();
}
}
}
}

69
S7.Net/PLC.cs
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@@ -39,6 +39,11 @@ namespace S7.Net
/// Slot of the CPU of the PLC
/// </summary>
public Int16 Slot { get; private set; }
/// <summary>
/// Max PDU size this cpu supports
/// </summary>
public Int16 MaxPDUSize { get; private set; }
/// <summary>
/// Returns true if a connection to the PLC can be established
@@ -158,7 +163,6 @@ namespace S7.Net
/// <returns>Returns ErrorCode.NoError if the connection was successful, otherwise check the ErrorCode</returns>
public ErrorCode Open()
{
byte[] bReceive = new byte[256];
_mSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
_mSocket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, 1000);
@@ -243,28 +247,33 @@ namespace S7.Net
return ErrorCode.WrongCPU_Type;
}
//COTP Setup
_mSocket.Send(bSend1, 22, SocketFlags.None);
if (_mSocket.Receive(bReceive, 22, SocketFlags.None) != 22)
var response = COTP.TPDU.Read(_mSocket);
if (response.PDUType != 0xd0) //Connect Confirm
{
throw new Exception(ErrorCode.WrongNumberReceivedBytes.ToString());
}
}
//S7ComSetup
byte[] bsend2 = { 3, 0, 0, 25, 2, 240, 128, 50, 1, 0, 0, 255, 255, 0, 8, 0, 0, 240, 0, 0, 3, 0, 3, 1, 0 };
_mSocket.Send(bsend2, 25, SocketFlags.None);
if (_mSocket.Receive(bReceive, 27, SocketFlags.None) != 27)
var s7data = COTP.TSDU.Read(_mSocket);
if (s7data.Length >= 2 && s7data[1] == 0x03) //Check for S7 Ack Data
{
throw new Exception(ErrorCode.WrongNumberReceivedBytes.ToString());
}
MaxPDUSize = (short)(s7data[18] * 256 + s7data[19]);
return ErrorCode.NoError;
}
throw new Exception(ErrorCode.WrongNumberReceivedBytes.ToString());
}
catch(Exception exc)
catch (Exception exc)
{
LastErrorCode = ErrorCode.ConnectionError;
LastErrorString = string.Format("Couldn't establish the connection to {0}.\nMessage: {1}", IP, exc.Message);
return ErrorCode.ConnectionError;
}
return ErrorCode.NoError;
}
/// <summary>
@@ -290,11 +299,12 @@ namespace S7.Net
public void ReadMultipleVars(List<DataItem> dataItems)
{
int cntBytes = dataItems.Sum(dataItem => VarTypeToByteLength(dataItem.VarType, dataItem.Count));
if (dataItems.Count > 20)
throw new Exception("Too many vars requested");
if (cntBytes > 222)
throw new Exception("Too many bytes requested"); // TODO: proper TDU check + split in multiple requests
//Is this really a limit?
//if (dataItems.Count > 20)
// throw new Exception("Too many vars requested");
if (cntBytes > MaxPDUSize - 18)
throw new Exception(string.Format("Too many bytes requested Requested: {0} Max {1}", cntBytes, MaxPDUSize)); //TODO: split in multiple requests
try
{
@@ -310,12 +320,10 @@ namespace S7.Net
_mSocket.Send(package.array, package.array.Length, SocketFlags.None);
byte[] bReceive = new byte[512];
int numReceived = _mSocket.Receive(bReceive, 512, SocketFlags.None);
if (bReceive[21] != 0xff)
throw new Exception(ErrorCode.WrongNumberReceivedBytes.ToString());
var s7data = COTP.TSDU.Read(_mSocket);
if (s7data[14] != 0xff) throw new Exception(ErrorCode.WrongNumberReceivedBytes.ToString());
int offset = 25;
int offset = 18;
foreach (var dataItem in dataItems)
{
int byteCnt = VarTypeToByteLength(dataItem.VarType, dataItem.Count);
@@ -323,7 +331,7 @@ namespace S7.Net
for (int i = 0; i < byteCnt; i++)
{
bytes[i] = bReceive[i + offset];
bytes[i] = s7data[i + offset];
}
offset += byteCnt + 4;
@@ -358,7 +366,7 @@ namespace S7.Net
int index = startByteAdr;
while (count > 0)
{
var maxToRead = (int)Math.Min(count, 200);
var maxToRead = (int)Math.Min(count, MaxPDUSize);
byte[] bytes = ReadBytesWithASingleRequest(dataType, db, index, maxToRead);
if (bytes == null)
return resultBytes.ToArray();
@@ -636,7 +644,7 @@ namespace S7.Net
int count = value.Length;
while (count > 0)
{
var maxToWrite = (int)Math.Min(count, 200);
var maxToWrite = (int)Math.Min(count, MaxPDUSize);
ErrorCode lastError = WriteBytesWithASingleRequest(dataType, db, startByteAdr + localIndex, value.Skip(localIndex).Take(maxToWrite).ToArray());
if (lastError != ErrorCode.NoError)
{
@@ -1063,13 +1071,12 @@ namespace S7.Net
_mSocket.Send(package.array, package.array.Length, SocketFlags.None);
byte[] bReceive = new byte[512];
int numReceived = _mSocket.Receive(bReceive, 512, SocketFlags.None);
if (bReceive[21] != 0xff)
var s7data = COTP.TSDU.Read(_mSocket);
if (s7data[14] != 0xff)
throw new Exception(ErrorCode.WrongNumberReceivedBytes.ToString());
for (int cnt = 0; cnt < count; cnt++)
bytes[cnt] = bReceive[cnt + 25];
bytes[cnt] = s7data[cnt + 25];
return bytes;
}
@@ -1129,8 +1136,8 @@ namespace S7.Net
_mSocket.Send(package.array, package.array.Length, SocketFlags.None);
int numReceived = _mSocket.Receive(bReceive, 512, SocketFlags.None);
if (bReceive[21] != 0xff)
var s7data = COTP.TSDU.Read(_mSocket);
if (s7data[14] != 0xff)
{
throw new Exception(ErrorCode.WrongNumberReceivedBytes.ToString());
}
@@ -1179,11 +1186,9 @@ namespace S7.Net
_mSocket.Send(package.array, package.array.Length, SocketFlags.None);
int numReceived = _mSocket.Receive(bReceive, 512, SocketFlags.None);
if (bReceive[21] != 0xff)
{
var s7data = COTP.TSDU.Read(_mSocket);
if (bReceive[14] != 0xff)
throw new Exception(ErrorCode.WrongNumberReceivedBytes.ToString());
}
return ErrorCode.NoError;
}

2
S7.Net/S7.Net.csproj
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@@ -77,9 +77,11 @@
</ItemGroup>
<ItemGroup>
<Compile Include="Conversion.cs" />
<Compile Include="COTP.cs" />
<Compile Include="Enums.cs" />
<Compile Include="PLC.cs" />
<Compile Include="Properties\AssemblyInfo.cs" />
<Compile Include="TPKT.cs" />
<Compile Include="Types\Bit.cs" />
<Compile Include="Types\Boolean.cs" />
<Compile Include="Types\Byte.cs" />

46
S7.Net/TPKT.cs Normal file
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@@ -0,0 +1,46 @@
using System;
using System.Net.Sockets;
namespace S7.Net
{
/// <summary>
/// Describes a TPKT Packet
/// </summary>
internal class TPKT
{
public byte Version;
public byte Reserved1;
public int Length;
public byte[] Data;
/// <summary>
/// Reds a TPKT from the socket
/// </summary>
/// <param name="socket">The socket to read from</param>
/// <returns>TPKT Instace</returns>
public static TPKT Read(Socket socket)
{
var buf = new byte[4];
socket.Receive(buf, 4, SocketFlags.None);
var pkt = new TPKT
{
Version = buf[0],
Reserved1 = buf[1],
Length = buf[2] * 256 + buf[3] //BigEndian
};
pkt.Data = new byte[pkt.Length - 4];
socket.Receive(pkt.Data, pkt.Length - 4, SocketFlags.None);
return pkt;
}
public override string ToString()
{
return string.Format("Version: {0} Length: {1} Data: {2}",
Version,
Length,
BitConverter.ToString(Data)
);
}
}
}