Perl Cookbook

Non-Forking Servers

Problem

You want a server to deal with several simultaneous connections, but you don’t want to fork a process to deal with each connection.

Solution

Keep an array of open clients, use select to read information when it becomes available, and deal with a client only when you have read a full request from it, as shown in Example 17.6.

Example 17-6. nonforker

#!/usr/bin/perl -w
# nonforker - server who multiplexes without forking use POSIX; use IO::Socket; use IO::Select; use Socket; use Fcntl; use Tie::RefHash; $port = 1685; # change this at will # Listen to port. $server = IO::Socket::INET->new(LocalPort => $port, Listen => 10 ) or die "Can't make server socket: $@\n"; # begin with empty buffers %inbuffer = (); %outbuffer = (); %ready = (); tie %ready, 'Tie::RefHash'; nonblock($server); $select = IO::Select->new($server); # Main loop: check reads/accepts, check writes, check ready to process while (1) { my $client; my $rv; my $data; # check for new information on the connections we have # anything to read or accept? foreach $client ($select->can_read(1)) { if ($client == $server) { # accept a new connection $client = $server->accept(); $select->add($client); nonblock($client); } else { # read data $data = ''; $rv = $client->recv($data, POSIX::BUFSIZ, 0); unless (defined($rv) && length $data) { # This would be the end of file, so close the client delete $inbuffer{$client}; delete $outbuffer{$client}; delete $ready{$client}; $select->remove($client); close $client; ...