Writing a 2-byte integer to a stream?

Question

I'm trying to interact with an application over the network which uses a simple protocol. I have to send a header that looks like this:

2 bytes = Data Length (including Request Type)
1 byte = Request Type

I'm taking both parameters as integers:

private static void WriteHeader(Stream buf, int length, int requestType) {
    buf.Write(BitConverter.GetBytes(length), 0, 2);
    buf.WriteByte((byte)requestType);
}

I'm calling it like this:

byte[] outBuf = new byte[256];
using (MemoryStream outStream = new MemoryStream(outBuf)) {
    // Socket connection stuff here
    WriteHeader(outStream, 1, 110);
    sock.Send(outBuf);
    // Receive stuff here, never returns
}

I don't get any kind of exception when calling this method or sending outBuf over a socket, but the network application never responds. I can query it with other programs, though, so I'm fairly certain that it's because my header isn't being written correctly.

Am I doing something wrong when writing the values?

EDIT: Added MemoryStream code

Answer 1

What type of stream is it? If its buffering your input, the data may never actually be sent across the wire.

Edit:

BitConverter.GetBytes(1) gives you [1, 0, 0, 0], from which you are passing [1,0]. Maybe its an endian-ness issue. Try sending [0,1] as your header.

Answer 2

I suspect you need to make your length a short. When you wrtie the int to the stream I suspect you're only going to get the top two bytes since the int is 4 bytes and you're only writing two of them to buf.

Answer 3

Could there be endian-ness issues between your client and the server? You could try capturing the network traffic with Wireshark or similar tool, then compare the packets sent/received using your client versus some other application that communicates successfully.

Answer 4

Try a NetworkStream:

void WriteHeader(Stream s, int len, int cmd) {
    var buf = new byte[3];
    s.Write(BitConverter.GetBytes((UInt16)len));
    s.WriteByte((byte)cmd);
}

var ns = new NetworkStream(sock);
WriteHeader(ns, 1, 110);

Answer 5

I can think of three sources of errors in this code:

• endianness problems: what is the byte order for the 2 bytes length that you send, and are you certain that GetBytes gives the bytes in the right order?
• packet size: you are sending 256 bytes of data, even though your message is only 3 bytes in size.
• payload: you don't put any payload in the message, but message 110 may require additional data.