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POUsing async sockets on Windows Server 2008 R2 causes 100% CPU usage
 

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    <p>I have a fairly generic C# socket server that uses the asynchronous methods of the socket classes - BeginAccept(), BeginReceive(), etc. This server has been working great for the last 4 years at many customer sites running Win Server 2003. Recently I installed it on a Windows Server 2008 R2 server, 64-bit. Everything looks fine until the first client connects and issues a BeginReceive() and a BeginAccept() call in the accept handler. When this happens, the CPU usage spikes to 100% and stays that way until I close the listening socket.</p> <p>Not sure that it matters, but the server is running in a virtual machine.</p> <p>Have done a lot of testing, but nothing seems to help. Using Process Explorer, I can see that two threads are spun up shortly after the BeginReceive()/BeginAccept() calls, and they are the ones that are consuming the processor. Unfortunately, I am not able to reproduce this problem on my Win7 64-bit workstation.</p> <p>I have done a lot of research, and all that I have found so far is the following two KB articles that imply that Server 2008 R2 may have an issue with the TCP/IP components, but they are only available as hot fixes: KB2465772 and KB2477730. Am reluctant to have my customer install them until I am more certain that they will fix the issue. </p> <p>Has anyone else had this problem? If so, what did you have to do to resolve this issue?</p> <p>Here is the method that I believe causes the situation:</p> <pre><code>private void AcceptCallback(IAsyncResult result) { ConnectionInfo connection = new ConnectionInfo(); try { // Finish accept. Socket listener = (Socket)result.AsyncState; connection.Socket = listener.EndAccept(result); connection.Request = new StringBuilder(256); // Start receive and a new accept. connection.Socket.BeginReceive(connection.Buffer, 0, connection.Buffer.Length, SocketFlags.None, new AsyncCallback(ReceiveCallback), connection); _serverSocket.BeginAccept(new AsyncCallback(AcceptCallback), listener); // CPU usage spikes at 100% shortly after this... } catch (ObjectDisposedException /*ode*/) { _log.Debug("[AcceptCallback] ObjectDisposedException"); } catch (SocketException se) { connection.Socket.Close(); _log.ErrorFormat("[AcceptCallback] Socket Exception ({0}: {1} {2}", connection.ClientAddress, se.ErrorCode, se.Message); } catch (Exception ex) { connection.Socket.Close(); _log.ErrorFormat("[AcceptCallback] Exception {0}: {1}", connection.ClientAddress, ex.Message); } } </code></pre>
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