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From: lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall)
Newsgroups: comp.lang.perl
Subject: Re: UDP
Message-ID: <9032@jpl-devvax.JPL.NASA.GOV>
Date: 6 Aug 90 22:03:45 GMT
References: <1990Aug6.144416.29167@uvaarpa.Virginia.EDU>
Reply-To: lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall)
Organization: Jet Propulsion Laboratory, Pasadena, CA
Lines: 65

In article <1990Aug6.144416.29167@uvaarpa.Virginia.EDU> worley@compass.com writes:
: Is there any way to communicate with a server that use UDP (rather than
: TCP) using Perl?

Yes, but it's unreliable.   :-)

I do it regularly.  Here's a client that will send to a UDP echo port.
You can either use a connected socket or a send with the optional "to"
argument.  You should also be able to substitute a recv for the read.

Larry

#!/usr/bin/perl

($host) = @ARGV;
die "usage: $0 hostname\n" unless $host;

$pat = 'S n C4 x8';

$stream = 1;
$datagram = 2;

$inet = 2;

$tcp = 6;
$udp = 17;

($name,$aliases,$port) = getservbyname('echo','udp');

$SIG{'INT'} = 'dokill';

if ($host =~ /^\d+\./) {
    @bytes = split(/\./,$host);
}
else {
    ($name,$aliases,$addrtype,$length,@addrs) = gethostbyname($host);
    die "Can't lookup $host\n" unless $name;
    @bytes = unpack("C4",$addrs[0]);
}

$this = pack($pat,$inet,0,    0,0,0,0);
$that = pack($pat,$inet,$port,@bytes);

socket(S,2,$datagram,$udp) || die "socket: $!\n";
bind(S,$this) || die "bind: $!\n";
connect(S,$that) || die "connect: $!\n";

select(S); $| = 1; select(stdout); $| = 1;

if ($child = fork) {
    print "Remote $host# ";
    while (<STDIN>) {
	print S;
    }
    sleep 2;
    do dokill();
}
else {
    while (read(S, $_, 32767)) {
	print;
	print "Remote $host# ";
    }
}

sub dokill { kill 9,$child if $child; }