Client Socket won't disconnect?!

[Sparky74]

Hi. Can somebody please help me - I cannot get my TCP client application to close its socket one I attempt a send.

It will close the socket fine if I don't call Send or BeginSend. Soon as I do, it won't close.

Thank you

 
using System;
using System.Collections.Generic;
using System.Text;
using System.Threading;
using System.Net.Sockets;
using System.Net;
 
namespace SockTest
{
  class SockTest
  {
    public static ManualResetEvent connectDone;
    public static ManualResetEvent sendDone;
    public static Socket           socket;
    public static IPAddress        remoteIPAddress;
    public static IPEndPoint       remoteEndPoint;
 
    //------------------------------------------------------------------------------------
    // ConnectCallback()
    //------------------------------------------------------------------------------------
    private static void ConnectCallback( IAsyncResult ar )
    {
      Socket s = (Socket) ar.AsyncState;
      s.EndConnect( ar );
      connectDone.Set();
    }
 
    //------------------------------------------------------------------------------------
    // SendCallback()
    //------------------------------------------------------------------------------------
    private static void SendCallback( IAsyncResult ar )
    {
      Socket s = (Socket) ar.AsyncState;
      s.EndSend( ar );
      sendDone.Set();
    }
 
public static Byte[]  abTest =
{
  0x59, 0x00, 0x38, 0x00, 0x6F, 0x30, 0x00, 0x77, 0x30, 0x30, 0x31, 0x31, 0x32, 0x35, 0x37, 0x00,  
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x30,  
  0x36, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};
 
    static void Main( string[] args )
    {
      Byte[] asBytes  = new Byte[ 4 ];
 
      asBytes[ 0 ] = 127;
      asBytes[ 1 ] = 0;
      asBytes[ 2 ] = 0;
      asBytes[ 3 ] = 1;
 
      connectDone     = new ManualResetEvent( false );
      sendDone        = new ManualResetEvent( false );
      remoteIPAddress = new IPAddress( asBytes );
      remoteEndPoint  = new IPEndPoint( remoteIPAddress, 2005 );
 
      socket          = new Socket( AddressFamily.InterNetwork, 
                                    SocketType.Stream, 
                                    ProtocolType.Tcp );
 
      socket.BeginConnect( remoteEndPoint, ConnectCallback, socket );
 
      if( ! connectDone.WaitOne( 2000, false ) )
      {
        Console.WriteLine( "Connect failed" );
        return;
      }
 
      // Below line of code causes the socket to NOT close when socket.Close()
      // is called!!
      socket.Send( abTest, 0 );
 
/* This doesn't work either
      socket.BeginSend( abTest, 
                        0, 
                        abTest.Length, 
                        SocketFlags.None, 
                        new AsyncCallback( SendCallback ), socket );
 
      if( ! sendDone.WaitOne( 2000, false ) )
      {
        Console.WriteLine( "Send failed" );
      }
 */
 
      socket.Close();
 
      Console.WriteLine( "Press a key to STOP" );
      Console.ReadLine();
    }
  }
}
 
 
 

[Sparky74]

Hmmm... Actually, the information I stated in my previous post is not entirely true..

The server application I am connecting to is an old MSVC 6 C++ application that used Win32 Winsock calls (select(), recv(), send etc).

My C# .NET client does close its connection when I connect to any other application (I just tried it on an MFC socket test server application).

The offending Win32 Winsock based server has been around for years.. I don't know why it isn't detecting the client disconnections from .NET socket client applications.

There must be a socket configuration parameter which causes this behaviour..??

[Sparky74]

Resolved!

For anyone experiencing the same problem, its dodgy old Win32 code usage.

The server application I'm using only tests for recv() returning zero in order to determine if a client has disconnected. The .NET client I am using results in recv() returning -1 (SOCKET_ERROR) and this wasn't being handled.

Hope this helps somebody else thats been in my boat.