C# TCP Async EndReceive() throws InvalidOperationException ONLY on Windows XP 32-bit
- by James Farmer
I have a simple C# Async Client using a .NET socket that waits for timed messages from a local Java server used for automating commands. The messages come in asynchronously and is written to a ring buffer. This implementation seems to work fine on Windows Vista/7/8 and OSX, but will randomly throw this exception while it's receiving a message from the local Java server:
Unhandled Exception: System.InvalidOperationException: EndReceive can only be called once for each asynchronous operation.
at System.Net.Sockets.Socket.EndReceive(IAsyncResult asyncResult, SocketError& errorCode)
at System.Net.Sockets.Socket.EndReceive(IAsyncResult asyncResult)
at SocketTest.Controller.RecvAsyncCallback(IAsyncResult ar)
at System.Net.LazyAsyncResult.Complete(IntPtr userToken)
...
I've looked online for this error, but have found nothing really helpful. This is the code where it seems to break:
/// <summary>
/// Callback to receive socket data
/// </summary>
/// <param name="ar">AsyncResult to pass to End</param>
private void RecvAsyncCallback(IAsyncResult ar)
{
// The exception will randomly happen on this call
int bytes = _socket.EndReceive(_recvAsyncResult);
// check for connection closed
if (bytes == 0)
{
return;
}
_ringBuffer.Write(_buffer, 0, bytes);
// Checks buffer
CheckBuffer();
_recvAsyncResult = _sock.BeginReceive(_buffer, 0, _buffer.Length, SocketFlags.None, RecvAsyncCallback, null);
}
The error doesn't happen on any particular moment except in the middle of receiving a message. The message itself can be any length for this to happen, and the exception can happen right away, or sometimes even up to a minute of perfect communication.
I'm pretty new with sockets and network communication, and I feel I might be missing something here. I've tested on at least 8 different computers, and the only similarity with the computers that throw this exception is that their OS is Windows XP 32-bit.
