public override bool ClientDecode(
ModbusCommand command,
ByteArrayReader body)
{
return(true);
}
/// <summary>
/// Encode the server-side command toward the master remote device
/// </summary>
/// <param name="command"></param>
/// <param name="body"></param>
/// <returns>True when the function operated successfully</returns>
public virtual bool ServerEncode(
ModbusCommand command,
ByteArrayWriter body)
{
return(false);
}
/// <summary>
/// Decode the incoming data from the remote master device
/// to a server-side command
/// </summary>
/// <param name="command"></param>
/// <param name="body"></param>
/// <returns>True when the function operated successfully</returns>
public virtual bool ServerDecode(
ModbusCommand command,
ByteArrayReader body)
{
return(false);
}
CommResponse IProtocolCodec.ServerDecode(CommDataBase data)
{
var server = (ModbusServer)data.OwnerProtocol;
ByteArrayReader incoming = data.IncomingData;
//validate header first
var length = incoming.Length;
if (length < 4)
{
goto LabelUnknown;
}
//address
var address = incoming.ReadByte();
if (address == server.Address)
{
//function code
var fncode = incoming.ReadByte();
if (fncode < CommandCodecs.Length)
{
//create a new command
var command = new ModbusCommand(fncode);
data.UserData = command;
command.QueryTotalLength = 2; //= addr + fn (no crc)
//get the command codec
var codec = CommandCodecs[fncode];
//decode the command, where possible
var body = new ByteArrayReader(incoming.ReadBytes(length - 4));
if (codec.ServerDecode(command, body))
{
//calculate the CRC-16 over the received stream
ushort crcCalc;
unchecked
{
crcCalc = (ushort)ModbusRtuCodec.Crc16.Compute(
((IByteArray)incoming).Data,
0,
command.QueryTotalLength);
}
//validate the CRC-16
ushort crcRead = ByteArrayHelpers.ReadUInt16LE(
((IByteArray)incoming).Data,
command.QueryTotalLength);
if (crcRead == crcCalc)
{
return(new CommResponse(
data,
CommResponse.Ack));
}
}
}
}
//exception
return(new CommResponse(
data,
CommResponse.Ignore));
LabelUnknown:
return(new CommResponse(
data,
CommResponse.Unknown));
}