CommResponse IProtocolCodec.ServerDecode(CommDataBase data)
{
var server = (ModbusServer)data.OwnerProtocol;
var incoming = data.IncomingData;
//validate header first
if (incoming.Length < 6)
{
goto LabelUnknown;
}
//transaction-id
var transId = incoming.ReadUInt16BE();
//protocol-identifier
var protId = incoming.ReadInt16BE();
if (protId != 0)
{
goto LabelIgnore;
}
//message length
var length = incoming.ReadInt16BE();
if (incoming.Length < (length + 6))
{
goto LabelUnknown;
}
//address
var address = incoming.ReadByte();
data.Address = server.AddressFromIncommingData ? address : server.Address;
if (server.CanHandleIncommingData(address))
{
//function code
var fncode = incoming.ReadByte();
if (!CommandCodecs.ContainsKey(fncode))
{
return(new CommResponse(null, CommResponse.Unknown));
}
//create a new command
var command = new ModbusCommand(fncode);
data.UserData = command;
command.TransId = transId;
//
var body = new ByteArrayReader(incoming.ReadToEnd());
//encode the command body, if applies
var codec = CommandCodecs[fncode];
if (codec != null)
{
codec.ServerDecode(command, body);
}
return(new CommResponse(
data,
CommResponse.Ack));
}
//exception
LabelIgnore:
return(new CommResponse(
data,
CommResponse.Ignore));
LabelUnknown:
return(new CommResponse(
data,
CommResponse.Unknown));
}
CommResponse IProtocolCodec.ServerDecode(CommDataBase data)
{
var server = (ModbusServer)data.OwnerProtocol;
var incoming = data.IncomingData;
//validate header first
var length = incoming.Length;
if (length < 4)
{
goto LabelUnknown;
}
//address
var address = incoming.ReadByte();
data.Address = server.AddressFromIncommingData ? address : server.Address;
if (server.CanHandleIncommingData(address))
{
//function code
var fncode = incoming.ReadByte();
if (CommandCodecs.ContainsKey(fncode))
{
//create a new command
var command = new ModbusCommand(fncode);
data.UserData = command;
command.QueryTotalLength = 6; //= addr + fn + offset + crc
//get the command codec
var codec = CommandCodecs[fncode];
//decode the command, where possible
var body = new ByteArrayReader(incoming.ReadBytes(length - 4));
codec.ServerDecode(command, body);
//calculate the CRC-16 over the received stream
ushort crcCalc = ByteArrayHelpers.CalcCRC16(
incoming.ToArray(),
0,
command.QueryTotalLength - 2);
//validate the CRC-16
var crcRead = ByteArrayHelpers.ReadInt16LE(
((IByteArray)incoming).Data,
command.QueryTotalLength - 2);
if (crcRead == (short)crcCalc)
{
return(new CommResponse(
data,
CommResponse.Ack));
}
}
}
//exception
return(new CommResponse(
data,
CommResponse.Ignore));
LabelUnknown:
return(new CommResponse(
data,
CommResponse.Unknown));
}
