Socket programming design problem

[David]

After programming with Python for a few hours, I've come up with some code:
http://p.shurl.net/3n. However, now I've realised there's a bit of a
problem with the original design.

I have a number of questions, if anybody could answer I'd be grateful.

a) Big problem, I can't see how to receive from more than one socket at
once. I need to do this so that data from the TCP connection can be sent
out on the UDP one and vice versa. Do I need a thread for each, or is
there some other way I can listen on two sockets at once (maybe
non-blocking ones?)

b) If the script dies prematurely, e.g. I mistyped something and Python
throws an exception, it is caught by the generic handler at the bottom.
However, the socket does not seem to be cleaned up properly, as if I try to
run it again immediately I get an error that it is still in use. lsof
doesn't show it in use though, which seems weird. Is there any particular
reason for this?

Thanks,

David

 

[John J. Lee]

a) Big problem, I can't see how to receive from more than one socket at
once. I need to do this so that data from the TCP connection can be sent
out on the UDP one and vice versa. Do I need a thread for each, or is
there some other way I can listen on two sockets at once (maybe
non-blocking ones?)

1. threads, yes
2. http://docs.python.org/lib/module-select.html (if on non-Windows system)
3. http://docs.python.org/lib/module-asyncore.html (ditto)
4. http://twistedmatrix.com/


Interesting but maybe not production-ready code:

1. http://kamaelia.sourceforge.net/Home
2. http://poshmodule.sourceforge.net/

b) If the script dies prematurely, e.g. I mistyped something and Python
throws an exception, it is caught by the generic handler at the bottom.
However, the socket does not seem to be cleaned up properly, as if I try to
run it again immediately I get an error that it is still in use. lsof
doesn't show it in use though, which seems weird. Is there any particular
reason for this?

Google for SO_REUSEADDR



John

 

[Dan Sommers]

a) Big problem, I can't see how to receive from more than one socket
at once. I need to do this so that data from the TCP connection can
be sent out on the UDP one and vice versa. Do I need a thread for
each, or is there some other way I can listen on two sockets at once
(maybe non-blocking ones?)

Try the select module:

http://www.python.org/doc/current/lib/module-select.html

Regards,
Dan