non-blocking listen on a tcp server

monkeyfish has asked for the wisdom of the Perl Monks concerning the following question:

Dear monks,

I've written a tcp server based on the examples in Perl Cookbook and using IO::Socket::INET. It blocks on accept() and then forks to handle each new connection as they come in.

while (($connection) = $server->accept()) {
# do fork stuff
[download]

All that works fine. Connection are made and the server can receive and send data.

while(<$connection>) {  # waits for data
# handle the incoming message
[download]

The problem is - each child process blocks while listening for data from the client.

i.e. the server cannot initiate sending data to the client until after it receives something.

This is a real problem as my clients are only sending data sporadically.

Can the "listen" for each connection behave in a non-blocking fashion?

Basically, I'd like to test if there's a message and if so, process it. If not, however, I'd like to have the option to 'do other stuff' like sending messages back to the client if necessary. Oh, and sleep for a bit.

Comment on non-blocking listen on a tcp server Select or Download Code

Replies are listed 'Best First'.
Re: non-blocking listen on a tcp server by almut (Canon) on Jun 09, 2010 at 18:14 UTC
`while(<$connection>) { # waits for data` [download] I think you want select, or the easier to use IO::Select.	[reply] [d/l]
Re^2: non-blocking listen on a tcp server by ikegami (Patriarch) on Jun 09, 2010 at 18:43 UTC
I'd avoid this route. Basically, it involves implementing a limited form of cooperative multitasking from scratch. Here are some examples: Example with sentinel ("\n") terminated messages Example with length-prefixed messages Update: I've added replies to the examples linked above that show simpler alternatives to using `select`.	[reply] [d/l]
Re^3: non-blocking listen on a tcp server by monkeyfish (Initiate) on Jun 09, 2010 at 22:57 UTC
Thanks alot folks. You're giving me good ideas. ikegami, I like the Coro option - the code is neat. I'm still trying to get my head around it though. The example doesn't appear to have the forking server but I need my server to handle multiple client connection simultaneously. Is that still an option when using Coro?	[reply]
Re^4: non-blocking listen on a tcp server by ikegami (Patriarch) on Jun 09, 2010 at 23:40 UTC
Re: non-blocking listen on a tcp server by ikegami (Patriarch) on Jun 09, 2010 at 18:34 UTC
There's also threads and Coro (cooperative multitasking)	[reply]
Re: non-blocking listen on a tcp server by zwon (Abbot) on Jun 09, 2010 at 18:22 UTC
Perhaps you should spend some time learning POE or AnyEvent.	[reply]
Re: non-blocking listen on a tcp server by bingos (Vicar) on Jun 10, 2010 at 21:07 UTC
And not forgetting IO::Async and IO::Lambda.	[reply]