The parent pid sends a string to the child pid, which the child prints out. The child then sleeps for 2 seconds before sending a string to the parent. Instead of locking up completaly the parent prints "Waiting...\n" until there is input for it to read.

I wrote this to encorperate it into a larger Tk script which I don't want freezing when it forks off to download information.

NOTE: This does not work on Windows (hence the name "Unix Sockets")!

The code is a based on of "pipe2" from perlipc. See also: IO::Socket, IO::Select, and perlipc.

#!/usr/bin/perl -w use strict; use Socket; use IO::Socket; use IO::Select; socketpair(CHILD, PARENT, AF_UNIX, SOCK_STREAM, PF_UNSPEC) or die "socketpair: $!"; CHILD->autoflush(1); PARENT->autoflush(1); my $pid; my $s = IO::Select->new(); $s->add(\*CHILD); if ( $pid = fork ) { close PARENT; print CHILD "Parent Pid $$ is sending this\n"; #chomp(my $line = <CHILD>); my $line; while ( 1 ) { if ( $s->can_read(0) ) { foreach my $handle ( $s->can_read(0) ) { recv($handle, $line, 1024, 0); } last; } print "Waiting...\n"; } chomp $line; print "Parent Pid $$ just read this: '$line'\n"; close CHILD; waitpid($pid, 0); } else { die "cannot fork: $!" unless defined $pid; close CHILD; chomp(my $line = <PARENT>); print "Child Pid $$ just read this: '$line'\n"; sleep 2; print PARENT "Child Pid $$ is sending this\n"; close PARENT; exit; }

Replies are listed 'Best First'.
Re: Non-Blocking Bidirectional Communication using Unix Sockets
by Anonymous Monk on Feb 09, 2015 at 20:57 UTC
    You keep using that word "non-blocking."
    I do not think it means what you think it means.

    perldoc -f sysread
    perldoc -f syswrite