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QuestionHow to use tcp keepalive to check the client is alive? Pin
wangningyu4-Jun-11 23:23
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AnswerRe: How to use tcp keepalive to check the client is alive? Pin
Code-o-mat5-Jun-11 22:55
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GeneralRe: How to use tcp keepalive to check the client is alive? Pin
Emilio Garavaglia6-Jun-11 3:41
MemberEmilio Garavaglia6-Jun-11 3:41 
Code-o-mat wrote:
2 hours is a lot of time, you might want to shorten that.


Dangerous: those timers are expected to be consistent on a very wide number of system, and -because of the way TCP works- there is no need to make it shorter.

The keep-alive is sent on a silent socket to let it be not-anymore silent. But the problem is ... why is it silent?

If there are data to let flow, TCP itself recover transmission error and - if that cannot be done - reports to the soket WSAENETRESET/WSAENOTCONN independently on every keep-alive feature.
If there are no data to let flow for long time, considering servers queue, routing tables, switches cam table, firewall caches, ARP table etc. assuming everything still works the same is risky. Better to close the socket, and reopen it again when furtherly needed, and use some "session layer command or data" (the application should define what the y should be) to track the state of the session or re-sync the client and the server.

In other words, the OP had better to implement a more robust application protocol that uses the underlying socket not just to transfer data, but also to exchange some status information about the existence and activity of the client and the server (this can be done more frequently) if he wants to promptly react to an unexpected event.

2 bugs found.
> recompile ...
65534 bugs found.
D'Oh! | :doh:


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Questionmysql error and UNICODE Pin
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