How to get status of socket when network cable disconnect from network adapter

I write a comunication program with c/s mode in C# ,server and client program on different computer. Today after client progarm connected to server progarm ,then I pulled out cable from network adapter (after this , client and server program didn't do anything), stranger thing happened. I found out socket of server program still keep connected status. and I use command "netstat -a -n" to retrieve network information ,and get information like following :

TCP 192.168.1.2:3645 开发者_JS百科192.168.1.3:1863 ESTABLISHED

192.168.1.2 (Server IP Address) 192.168.1.3 (Client IP Address)

Do anyone know the reason ? how to solve this problem . I wanna how server program can receive the event and close the socket when network cable of client computer has been pulled out.

Please give me some advices or solutions.

Thanks

I think it can be solved by using TCP keepalive. refrencehttp://tldp.org/HOWTO/TCP-Keepalive-HOWTO/overview.html

after connecting , set socket keepalive property . msdn say this switch default status is off , if set keepalive to on , socket will check the network status automaticly , and first check time is 2 hours after last operation on socket. but the time can be adjsut to short . then after first check , socket will servral times. if connection is down or died, socket will throw exception .

C# Source:

    uint dummy = 0;
    byte[] inOptionValues = new byte[Marshal.SizeOf(dummy) * 3];
    //set keepalive on
    BitConverter.GetBytes((uint)1).CopyTo(inOptionValues, 0); 
    //interval time between last operation on socket and first checking. example:5000ms=5s
    BitConverter.GetBytes((uint)5000).CopyTo(inOptionValues, Marshal.SizeOf(dummy));
    //after first checking, socket will check serval times by 1000ms.
    BitConverter.GetBytes((uint)1000).CopyTo(inOptionValues, Marshal.SizeOf(dummy) * 2);

    Socket socket = __Client.Client;
    socket.IOControl(IOControlCode.KeepAliveValues, inOptionValues, null);

I have checked. It's running ok.

You can't. The only reliable way to check connected status is to send data over the wire, so: Deal with connection failures during send/receive, and, optionally, periodically check for connection status by some form of ping, if you want connection status during idle periods.

Im a bit unsure but if you try to read data from the socket after you pulled the cable it will tell you that its not connected any more..