TcpListener Socket still active after program exits.

Question

I'm trying to stop a TCP Listener as my program is exiting. I do not care about any data that is currently active on the socket or any of the active client sockets.

The socket clean up code is essentially:

try
{
    myServer.Server.Shutdown(SocketShutdown.Both)
}
catch (Exception ex)
{
     LogException(ex)
}
myServer.Server.Close(0)
myServer.Stop()

myServer is a TCPListener

On some occasions, Shutdown will thrown an exception

System.Net.Sockets.SocketException: A request to send or receive data was disallowed because the socket is not connected and (when sending on a datagram socket using a sendto call) no address was supplied at System.Net.Sockets.Socket.Shutdown(SocketShutdown how)

Edit 2010-May-14

Upon further investigation, the exception can be thrown and the socket can be closed correctly.

Sometimes, even after the application exits netstat shows the socket is still in the LISTENING state.

I have not been able to create definitive reproduction scenario, it happens at seemingly random times.

Client Sockets are cleaned up independently.

Do you have any suggestions to help me make this socket die?

Answer 1

Try calling Stop before Close...

Answer 2

After your app exits, the socket cannot be in a listening state. It may be in a wait state, however; this is perfectly normal.

Answer 3

Use a finally block to call Close() in the event of an exception:

try
{
    myServer.Server.Shutdown(SocketShutdown.Both);
}
catch (Exception ex)
{
    LogException(ex);
}
finally
{
    myServer.Server.Close(0);
    myServer.Stop();
}

I'm also curious if manipulation of the underlying socket is required because of some specification you haven't mentioned? TCPListener/Client are designed you keep you from worrying about those communication mechanics in most cases.

Also, if this doesn't help, what ErrorCode is being returned by the SocketException?