Re: how to know if socket is still connected

On 2006-07-17, Cameron Laird <claird@xxxxxxxxx> wrote:

works well, but sometimes the server drops the connection. so,
what i need is something that will let me know if the
connection is still ok, if not will reconnect.

If the server has closed the connection, then a recv() on the
socket will return an empty string "", and a send() on the
socket will raise an exception.

what i thought, since it only lets you connect on a certain
port one at a time, that i could use a try-except to connect
every time, if it could not connect (because it already is)
then i would just continue on. But if it is not connected, it
would reconnect. that is what brings me here. Seems like it
would work, but is there a better way?

I don't see why the normal send() and recv() semantics aren't
sufficient.
.
.
.
Often normal send() and recv() semantics have been mistaught.
An alert alien, looking at other common APIs in isolation,
might reasonably wonder whether there is some sort of
still_ok_to_use() sort of check as part of TCP. As it happens,
of course, that doesn't fit with the rest of socket networking,
which takes the "modernist" approach of trying send() or recv(),
and reporting any exception.

On most Unices there are some obscure API features that can be
used to generate a SIGPIPE under some vaguely specified error
conditions (e.g. TCP keepalive timeout). I've only read about
them and never tried to use them, since I couldn't see anything
in the description of the features that was any benefit over
the nomral send() and recv() usage.

--
Grant Edwards grante Yow! Xerox your lunch
at and file it under "sex
visi.com offenders"!
.

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