bockman has asked for the wisdom of the Perl Monks concerning the following question:

Hello. I'm having trouble with perl sockets. I want to 'use Socket' and not IO::Socket, but whatever I did won't produce the correct output. Here is what I'm feeding to my server:

$ printf "\x05\x01\x00" | nc server port

Which doesn't produce any output on my server. Here's the code: 
#!/usr/bin/perl
use strict;
use integer;
use Socket;

my $port = 50000; # Port to bind to
my $FORK = 0;     # Do we fork?

my $proto = getprotobyname('tcp');
socket(SERVER, PF_INET, SOCK_STREAM, $proto) or die "socket:$!";
setsockopt(SERVER, SOL_SOCKET, SO_REUSEADDR, pack("l", 1)) or die
"setsockopt: $!";
bind(SERVER, sockaddr_in($port, INADDR_ANY)) or die "bind: $!";
listen(SERVER, SOMAXCONN) or die "listen: $!";

if($FORK)
{
        my $pid = fork();
        die "fork: $!" if $pid < 0;
        exit if $pid;
}

for(;my $paddr=accept(CLIENT, SERVER); close CLIENT) {
        my ($ver,$nm,$methods) = ();
        recv(CLIENT,$ver,1,0);
        recv(CLIENT,$nm,1,0);
        if($ver == 0x05 && $nm)
        {
                print "Okay, getting $nm methods\n";
                recv(CLIENT,$methods,$nm,0);
        }
}

exit;

[download]
What's wrong?

Replies are listed 'Best First'.
Re: Socket troubles
by serf (Chaplain) on Jan 22, 2006 at 19:35 UTC
    If you add use warnings; to the top of your code after use strict; you will find you get this error: 
     Argument "^E" isn't numeric in integer eq (==) at ./try.pl line 40.

    [download]
    When you do your connect. This could be a big clue for you :o)

    use warnings; is your friend!

    I think this should do what you want it to: 

        if ( $ver =~ /\x05/ && $nm ) {

    [download]
    or even: 
    my $x05 = sprintf "\x05"; # hex 05 as a raw character for ver test.

for ( ; my $paddr = accept( CLIENT, SERVER ); close CLIENT ) {

    my ( $ver, $nm, $methods ) = ();

    recv( CLIENT, $ver, 1, 0 );
    recv( CLIENT, $nm,  1, 0 );

    if ( $ver eq $x05 && $nm ) {
        print "Okay, getting $nm methods\n";
        recv( CLIENT, $methods, $nm, 0 );
    }

}

    [download]
    PS: your debugging could also be easier if you format your die statements more helpfully: 
    socket( SERVER, PF_INET, SOCK_STREAM, $proto ) ||
    die "Can't create socket: $!\n";

setsockopt( SERVER, SOL_SOCKET, SO_REUSEADDR, pack( "l", 1 ) ) ||
    die "Can't set socket option: $!\n";

bind( SERVER, sockaddr_in( $port, INADDR_ANY ) ) ||
    die "Can't bind to socket: $!\n";

listen( SERVER, SOMAXCONN ) ||
    die "Can't set max connections (listen): $!\n";

    [download]
[reply]
[d/l]
[select]
      Why isn't 5 numeric? 5 is a number.
[reply]

        Uhh, no x05 is not a number. It's a control character, ^E. If you want a number expressed, change the printf you are piping to netcat, e.g.,

        printf "510" | netcat 127.0.0.1 50000

        [download]

        Scott

[reply]
[d/l]

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