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Client Socket won't disconnect?!

20 New Member
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

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  2. using System;
  3. using System.Collections.Generic;
  4. using System.Text;
  5. using System.Threading;
  6. using System.Net.Sockets;
  7. using System.Net;
  9. namespace SockTest
  10. {
  11.   class SockTest
  12.   {
  13.     public static ManualResetEvent connectDone;
  14.     public static ManualResetEvent sendDone;
  15.     public static Socket           socket;
  16.     public static IPAddress        remoteIPAddress;
  17.     public static IPEndPoint       remoteEndPoint;
  19.     //------------------------------------------------------------------------------------
  20.     // ConnectCallback()
  21.     //------------------------------------------------------------------------------------
  22.     private static void ConnectCallback( IAsyncResult ar )
  23.     {
  24.       Socket s = (Socket) ar.AsyncState;
  25.       s.EndConnect( ar );
  26.       connectDone.Set();
  27.     }
  29.     //------------------------------------------------------------------------------------
  30.     // SendCallback()
  31.     //------------------------------------------------------------------------------------
  32.     private static void SendCallback( IAsyncResult ar )
  33.     {
  34.       Socket s = (Socket) ar.AsyncState;
  35.       s.EndSend( ar );
  36.       sendDone.Set();
  37.     }
  39. public static Byte[]  abTest =
  40. {
  41.   0x59, 0x00, 0x38, 0x00, 0x6F, 0x30, 0x00, 0x77, 0x30, 0x30, 0x31, 0x31, 0x32, 0x35, 0x37, 0x00,  
  42.   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  
  43.   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x30,  
  44.   0x36, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  
  45.   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  
  46.   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
  47. };
  49.     static void Main( string[] args )
  50.     {
  51.       Byte[] asBytes  = new Byte[ 4 ];
  53.       asBytes[ 0 ] = 127;
  54.       asBytes[ 1 ] = 0;
  55.       asBytes[ 2 ] = 0;
  56.       asBytes[ 3 ] = 1;
  58.       connectDone     = new ManualResetEvent( false );
  59.       sendDone        = new ManualResetEvent( false );
  60.       remoteIPAddress = new IPAddress( asBytes );
  61.       remoteEndPoint  = new IPEndPoint( remoteIPAddress, 2005 );
  63.       socket          = new Socket( AddressFamily.InterNetwork, 
  64.                                     SocketType.Stream, 
  65.                                     ProtocolType.Tcp );
  67.       socket.BeginConnect( remoteEndPoint, ConnectCallback, socket );
  69.       if( ! connectDone.WaitOne( 2000, false ) )
  70.       {
  71.         Console.WriteLine( "Connect failed" );
  72.         return;
  73.       }
  75.       // Below line of code causes the socket to NOT close when socket.Close()
  76.       // is called!!
  77.       socket.Send( abTest, 0 );
  79. /* This doesn't work either
  80.       socket.BeginSend( abTest, 
  81.                         0, 
  82.                         abTest.Length, 
  83.                         SocketFlags.None, 
  84.                         new AsyncCallback( SendCallback ), socket );
  86.       if( ! sendDone.WaitOne( 2000, false ) )
  87.       {
  88.         Console.WriteLine( "Send failed" );
  89.       }
  90.  */
  92.       socket.Close();
  94.       Console.WriteLine( "Press a key to STOP" );
  95.       Console.ReadLine();
  96.     }
  97.   }
  98. }
Jun 28 '07 #1
2 2258
20 New Member
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..??
Jun 29 '07 #2
20 New Member

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.
Jun 29 '07 #3

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