Question

I am using Named Pipes to transfer data from a client (C++) to a server (C#), the client does the following:

// C++ Client sending message
struct MESSAGE
   {
   char    cCommand[8];
   string  sParameter;
   };

MESSAGE msg;
strcpy(msg.cCommand, "COMMAND");
strcpy(msg.sParameter, "DO SOMETHING");

DWORD dwWrote = 0;
WriteFile (hpipe, &msg, sizeof(msg), dwWrote, NULL);


// Then, at the receiving end the C# server recieve message:
IntPtr chRequest;
bool fSuccess = ReadFile(hPipeInst, chRequest, uSize, cbRead, OverlappedPtr);
if (fSuccess)
        byte[] temp = Encoding.ASCII.GetBytes(Marshal.PtrToStringAnsi(chRequest));

Now, at the receiving end, I need to transform the temp (byte[]) back into the STRUCT or something equivalent so I can access the members cCommand and sPatameter – but at this point I have no clue how to proceed… In reality doesn’t need to be a struct, I just need to extract the data itself.

Note – the STRUCT MESSAGE is something I came up with, meaning that it can be changed if a different format would be helpful in the reconstruction (add the length of sParameter for example?), I just need a COMMAND and PARAMETER to be transfered in a single block (if possible).

Requirements are simple:
– COMMAND is a fixed-length 8-characters long string that indicates what action needs to be performed
– PARAMETER is a variable-length (unless this causes issues) parameter dependant on each COMMAND

For example:
COMMAND = TRANS

PARAMETER = C:\FILE.txt C:\NewFolder\FILE.TXT

(this is just to illustrate, there are a lot more applications)

If possible I would like to extract it as a chunk of data (byte[]) and then pass it along to my application where it could be decomposed, not a fan of reading in the size, then a field, then a size, then a field – that requires that my Communication be overly linked with my implementation.

If there is a more suitable way to implement this transfer please let me know… advice would be welcome…
Any help would be much appreciated.
Thanks,

Answer 1

If you have the definitions of the struct in c++ you can define it in c# (it may require a little finagling). Then just read the size off of the socket and use Marshal.PtrToStructure to marshal it to the c# defined structure.

/* Define you structure like this (possibly) */
struct MESSAGE
{
  [MarshalAs(UnmanageType.ByValArray, SizeConst=8)]
  byte[]    cCommand;
  [MarshalAs(UnmanagedType.LPStr)]
  string  sParameter;
};

/* Read data into an instance of MESSAGE like this */
byte[] bytes = new byte[Marshal.SizeOf(MESSAGE)];

socket.Receive(bytes, 0, bytes.Length);
IntPtr ptr = Marshal.AllocHGlobal(bytes.Length);

try
{
    Marshal.Copy(bytes, 0, ptr, bytes.Length);
    m = (MESSAGE)Marshal.PtrToStructure(ptr, typeof(MESSAGE));
}
finally
{
    Marshal.FreeHGlobal(ptr);
}