Experimental Physics and
Industrial Control System

Dirk Zimoch via Core-talk <[email protected]> · Thu, 05 Sep 2019 06:49:37 -0000

4. Was the problem. send does not fail until some time later. But than messages are already lost.
So my fix is not to rely on send failing but on recv returning EOF.
SO_KEEPALIVE has a default timeout of 2 hours and you cannot change it per socket but only system wide. It is totally useless for solving the problems with lost messages. It is there to allow to clean up stale connections and not to run out of file descriptors in server programs that are constantly running. But that's about all. So it may help the log server but not the client.

The problem I solve here is that send succeeds until the FIFO is full, just as you pointed out in 4. and 5.

I cannot confirm 2 though. My tests with ncat as a server have shown that send does not detect immediately when the server has exited (and thus the kernel has closed the socket).

But leaving discussions about how TCP is supposed to work aside, my main argument for this change is: Now it works, before it didn't.
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https://code.launchpad.net/~dirk.zimoch/epics-base/+git/epics-base/+merge/372043
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System