Detection broken tcp connection

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2 total messages Started by Wouter Visscher Wed, 27 Jan 1993 14:14

#6960

Author: Wouter Visscher
Date: Wed, 27 Jan 1993 14:14

24 lines
1296 bytes

Dear wizards,

I have te following situation:
A tcp connect, with keep_alive option and non blocking mode.

If the ethernet fails ( pull out a drop cable for instance) I want
my application to detect a broken connection.

Want can I expect in my application:
A - from a select
B - from a send
C - form a recv
D - signals
E - Any other means to determine the broken connection

Also a indication of the times involved on sunos 4.1 .

The manuals are not to clear on this subject, testing showed  the above calls
i.e. select, send, recv did not return error codes indicating a problem.
Mind you if an error code is only return once I might have missed it during
this test


#include <stddisclaimer.h>       This might not be the view of my employer.

Re: Detection broken tcp connection

#6957

Author: Eric E. Johnson
Date: Wed, 27 Jan 1993 21:09

31 lines
1658 bytes

wv@dasc.nl (Wouter Visscher) writes:

>The manuals are not to clear on this subject, testing showed  the above calls
>i.e. select, send, recv did not return error codes indicating a problem.
>Mind you if an error code is only return once I might have missed it during
>this test

Lucky you.  I just learned the answer to this question last week.

If your sockets are...

Blocking... then just wait for a read to return zero bytes, indicating a
broken connection.  I don't use blocking sockets, so I have no
experience with this method.

NonBlocking... Watch for select() to claim that one of the sockets can
be read from by setting the appropriate descriptor bit.  Then, when you
go to read the socket via a non blocking read, you will get zero bytes
back when the socket connection is broken.  Keep in mind that normally,
a zero means, "No new data".  It only means "Broken connection" when
select() indicates that the socket should be read from.

This should do the trick.

Eric

-- 
Eric E Johnson             | "Sigsoft is a black hole of ambition, everything
ejohnson@a.cs.uiuc.edu     |  gets sucked in, and nothing comes out." - Me

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