Question

Problem

I have PHP client which sends a image file to a C# socket server. My problem is about 30% of the time the file is partially transferred and stops.

PHP END ->

$file = file_get_contents('a.bmp');
socket_write($socket,$file);

C# END ->

 int l= Socket.Receive(buffer, buffer.Length, SocketFlags.None);
  //create the file using a file stream

How can I always transfer the full file without intermediate states? And why does it happen?

Answer 1

From the documentation for Socket.Receive:

If you are using a connection-oriented Socket, the Receive method will read as much data as is available, up to the number of bytes specified by the size parameter. If the remote host shuts down the Socket connection with the Shutdown method, and all available data has been received, the Receive method will complete immediately and return zero bytes.

This means you may get less than the total amount. This is just the way sockets work.

So if if you get a partial read, you should call Socket.Receive again. You can use the overload of Socket.Receive to continue reading into the same buffer.

Here is an article that shows how “keep reading” until you get what you want:

• Socket Send and Receive

If you don’t know how big the data is, you must keep reading until Socket.Receive returns zero.