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non blocking socket

Posted on 2000-04-12
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Last Modified: 2012-05-04
i have made server in linux and my client are windows based. now when my windows client connect to my server and i remove the cable from the ethernet card, then also my server is anable to detect that cable break. I want to make myserver such that so it can detect the cable break and logout that particular user. I have used KEEPALIVE socket option but it is not working..(I have made server in 'C'language under linux through socket programming)...
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Question by:abhishekpatel
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munsie earned 50 total points
ID: 2724795
well, you're probally TCP based for your connection.  breaking the physical connection doesn't break the logical connection.

Here's what I recommend.  Define some message that your client will send once every x seconds.  This message should be ignored by the server, but will cause a timer to reset.  If you miss 2 or more of these heartbeats, have the server close up the connection.

the easiest way to do this is to call select() on the socket with a timeout.  Se t the timeout to the same value on the client and server.  When you get a timeout, increment your missed count.

Another slightly different way is to just wait for data from the client with the timeout set, and any data sent would clear your missed count.  This would only work where the client sends data on a pretty regular interval to the server.

If the server is sending data to the client, eventually the send buffer will fill up and you will block while trying to send.  You could then use a timeout to determine that the client isn't there anymore.

good luck,
dennis
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by:abhishekpatel
ID: 2729438
If i make the my server to wait for any data from
client that are to be used to detect the existence
of client then the "recv" call waits indifinetly if client will not send any data so my server is enable to detect it. Using "select" is good idea.
Can you guide me how to use "select" , I have tried but i don't get success.

Here is how my server works :-

        my server will fork a new process as soon as
any client connects to it so the new process will
handle all the transaction on that channel.

can you help me in implementing "select" in my server
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