Wise Monks,

I have a simple problem (I think). I would like to be actively listening on a UDP port (server) and be able to send to specified UDP ports (client) based on <STDIN>.

Code below works on unix and linux, but on Win32 (ActiveState 5.8.0 805, Win2k) the following code seems to block no matter what I try on the $sock->recv. This prevents any $sock->send from the child (why is that?).

Advice, code, gladly accepted (I've tried to implement different iterations on forking, low-level socket defines and IO::Select for 20+ hours, but no luck)!! 

#!/usr/bin/perl
# biclient - bidirectional forking client   perl_book\cookbook\ch17_11
+.htm
use IO::Socket;
use English;
use strict;

my ($lport, $host, $port, $kidpid, $sock, $line, $msg, $MAXLEN);
$MAXLEN = 1024;

unless (@ARGV == 3) { die "usage: $0 listen_port dest_host  dest_port\
+n" }
($lport, $host, $port) = @ARGV;

# create a udp connection to the specified host and port
$sock = IO::Socket::INET->new(Proto     => "udp",
                              LocalPort => $lport,
                              PeerAddr  => $host,
                              PeerPort  => $port)
       or die "can't connect to port $port on $host: $!";

print STDOUT "[Listening on $lport, Connected to ($host:$port)]\n";

# split the program into two processes, identical twins
die "can't fork: $!" unless defined($kidpid = fork());

if ($kidpid) {
    print STDOUT "Parent $PID started\n";

    # parent copies the socket to standard output
    while ($sock->recv($msg, $MAXLEN)) {
        print "\nReceived from ($host:$port) \"$msg\" \n";
    }
    kill("TERM" => $kidpid);        # send SIGTERM to child

} else {
    print STDOUT "Child $PID started\n";
    print $sock "Child $PID started";

    # child copies standard input to the socket
    while ($line = <STDIN>) {
        chomp($line);  #print STDOUT "You entered: $line\n";
        print $sock $line;
    }
}
exit;

[download]

Also, it seems that once a connection is made from perl program to another, I cannot connect another perl program to the same socket (ie. listen in on the datagrams). Is this part of the design, or can this be worked-around?

Thanks in Advance!!
Steve

In reply to UDP bidirectional client by sbrandt

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