Sockets and time-outs

[Donn Cave]

Quoth Ulf Engstrøm <ulf.engstrom at b2b-link.com>:
| I'm using the socket module for a program, but there's one thing that I want
| to improve on it.
| The client side of this sends data to the server and always get a reply
| back, but sometimes the server sends something that wasn't requested of the
| reply comes in two sends. Thus I need to read the socket sometimes to see if
| there's something waiting. Using recv() is great for getting a reply I know
| is there, but when using it and there's no message there it takes an awfully
| long time to time out and waiting for this time-out blocks the sending on
| the same socket. Is there any way to set a shorter time-out (basically just
| check for 2 secs or so) or is there an other function for this?

I would use select, like this for a very simple example:

    import select
    ...
    input = [srv_con]
    input, output, error = select.select(input, [], [], 2.0)
    if srv_con in input:
        srv_input = srv_con.recv(8192)

Now depending on your protocol, it may be convenient to put this select
in a very central place in the system.  Protocols like that, where the
dialogue doesn't simply trade back and forth, are somewhat more challenging.

	Donn Cave, donn at u.washington.edu