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Winsock : How do I know when other host closes connection with me?

Posted on 1998-12-18
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Last Modified: 2010-04-15
Hello,

I'm beginner to Winsock programming. I wrote a "chat" program. It works but I want to know whenever the connection is closed by other host. For now, I check this by trying sending something to other host. If I can send without any error then it still alives. That's not a good and convenient methode.

Can anyone show me better methode to verify a connection without sending?
For instance something like getting the state of a connection.

Thank you.
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Question by:toannds
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Accepted Solution

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rdelfino earned 50 total points
ID: 1255285

There's another way. You try recv().

If the connection is no longer alive you will get 0 bytes received
or an error.

I hope it helps

Reginaldo

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Expert Comment

by:jhance
ID: 1255286
rdelfino,

Wrong answer.  Just because recv() returns 0 bytes, doesn't mean the connection has closed.  There just may be 0 bytes available at that time.

Under Windows, the right way to do it is to use WSAAsyncSelct() and specify the FD_CLOSE event.  If WSAGETSELECTERROR returns 0 for the FD_CLOSE event, then the socket was closed gracefully.  If an error value of WSAECONNRESET is returned, the socket was aborted.
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Author Comment

by:toannds
ID: 1255287
Thanks, I'll try...
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Expert Comment

by:jhance
ID: 1255288
It's also too bad you accepted an incorrect answer...
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Author Comment

by:toannds
ID: 1255289
Thanks jhance!

Now I have completed my program with new concept: event notifications. It works perfectly. When other host close connection, I receive immediately FD_CLOSE.
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Expert Comment

by:jhance
ID: 1255290
Alas, it's too bad you accepted an incorrect answer...
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Author Comment

by:toannds
ID: 1255291
I don't understand what you said. My program used WSAAsyncSelect() and worked well. I wanna give you more points :-)
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Expert Comment

by:jhance
ID: 1255292
You didn't give ME any points.  You accepted rdelfino's incorrect answer rather than rejecting it.

So he gets the points and I don't.
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Author Comment

by:toannds
ID: 2026483
I'm so sorry jhance.

For a long time I could not access to this site due to the stupid firewalls of my country. I was a beginner to this forum at that time so I didn't know clearly how to give you points. And by accident we meet again at my question

http://www.experts-exchange.com/jsp/qShow.jsp?ta=mfc&qid=10202631 

Now I know my mistake so I wanna give you more points in that question.

Please forgive me.
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