#!/usr/bin/perl

use Socket;

$addr = shift;
$port = shift;
die "Usage; $0 <ip address> <port number>\n" unless ($addr and $port);

$proto = getprotobyname('tcp');
print "proto=[$proto]\n";
print "AF_INET=[", AF_INET, "]\n";
print "SOCK_STREAM=[", SOCK_STREAM, "]\n";

#*******************************************************************
print "\nConnect using sockaddr_in method...\n";
$paddr = sockaddr_in($port, pack('C4', split('\.', $addr)));
printf "paddr=[%d, %d, %d.%d.%d.%d]\n", unpack('S n C4', $paddr);

socket(SOCK, AF_INET, SOCK_STREAM, $proto) || die "socket: $!\n";
connect(SOCK, $paddr) || die "connect: $!\n";

print "Connection to $addr:$port established\n";
close (SOCK) || die "close: $!";

#*******************************************************************
print "\nConnect using pack method...\n";
$paddr = pack('S n C4 x8', AF_INET, $port, split('\.', $addr));
printf "paddr=[%d, %d, %d.%d.%d.%d]\n", unpack('S n C4', $paddr);

socket(SOCK, AF_INET, SOCK_STREAM, $proto) || die "socket: $!\n";
connect(SOCK, $paddr) || die "connect: $!\n";

print "Connection to $addr:$port established\n";
close (SOCK) || die "close: $!\n";

exit;
[download]

I've run this test script on a variety of systems (Solaris, HP-UX, Redhat, RHEL, OS X 10.3/10.4) and both "connection methods" work fine... all EXCEPT for OS X 10.5/9A527 (aka Leopard). When I run the above test script on my MacBook Pro running OS X Leopard, I get the following results.

$ connect_test 127.0.0.1 22
proto=[6]
AF_INET=[2]
SOCK_STREAM=[1]

Connect using sockaddr_in method...
paddr=[512, 22, 127.0.0.1]
Connection to 127.0.0.1:22 established

Connect using pack method...
paddr=[2, 22, 127.0.0.1]
connect: Address family not supported by protocol family
[download]

My first thought, when I see the decoded value of $paddr after the sockaddr_in() call, is that AF_INET is supposed to be 512 on Leopard, but if that's true, why does AF_INET return 2?

Looking at /usr/include/sys/socket.h, where AF_INET is defined, the value is 2... the same thing AF_INET returns.

Also, looking in Socket.xs, in the pack_sockaddr_in() function, near the bottom, it sets sin.sin_family = AF_INET. So how is that sockaddr_in() eventually encodes 512? Am I decoding $paddr incorrectly?

I've tried this test on Leopard using the perl that comes with the OS (perl-5.8.8) and I've compiled 5.8.0, 5.8.6 and 5.8.8 myself (using "Configure -ds -e") and the results are the same.