in reply to Re: two-way socket works once only?
in thread two-way socket works once only?

Here's a example server and socket:

server.pl

use strict;
use warnings;

use IO::Socket ();

my $listen_fh = IO::Socket->new(
    Domain    => IO::Socket::AF_INET(),
    Proto     => 'tcp',
    LocalAddr => '127.0.0.1',
    Listen    => 1,
) or die("Unable to create listening socket: $!$/");

print('Listening on port ', $listen_fh->sockport(), '.', $/);

my $client_fh = $listen_fh->accept()
or die("Unable to accept a connection: $!$/");

print('Accepted a connection from ', $client_fh->peerhost(), ':', $cli
+ent_fh->peerport(), '.', $/);

while (<$client_fh>) {
   print $client_fh uc($_);
}

print('Connection closed by client or by error.', $/);

[download]

client.pl


use strict;
use warnings;

use IO::Socket ();

my $peer_port = shift(@ARGV)
or die("Specify the port on the command line.$/");

my $server_fh = IO::Socket->new(
    Domain   => IO::Socket::AF_INET(),
    Proto    => 'tcp',
    PeerAddr => '127.0.0.1',
    PeerPort => $peer_port,
) or die("Unable to connect to server: $!$/");

print('Connected to ', $server_fh->peerhost(), ':', $server_fh->peerpo
+rt(), '.', $/);

print('Type stuff to be uppercased by server. Blank line to exit.', $/
+);

for (;;) {
   last if (!defined($_ = <STDIN>) || $_ eq $/);
   print $server_fh $_;
   last if (!defined($_ = <$server_fh>));
   print;
}

print('Connection closed by server or by error or by request.', $/);

[download]

Replies are listed 'Best First'.
Re^3: two-way socket works once only?
by wolfger (Deacon) on Nov 23, 2004 at 19:35 UTC
    I'm going over your code for clues that may help me. In the meantime, here is the code I am working on. Server.pl works fine as is, but if I try to put the code inside a while loop (I have tried both inside the socket open/close calls and outside) it quits working.

    edit: I changed my server.pl a bit based on what I saw in your example. This does not work. The while loop goes through the first iteration fine, and hangs up the second time through with a (error|warning) message of "Use of uninitialized value in substitution (s///) at /clocal/mptsgrp/user/mptsuser/scripts/guipartner.pl line 24, <GEN1> line 2."
    The print statements I included for debug show that $incoming matched /.+/ even after it was set to "" on the first iteration, but it did fail the $command[0] eq "check" test. The killer, though, is that the while loop stopped there. "Hi" was never printed a third time. :-( 
    #!/usr/bin/perl
use strict;
use warnings;
use IO::Socket;
my $incoming;
my $check;
my @check;
my @command;
my $new_sock;

my $sock = new IO::Socket::INET (
                LocalPort => '8888',
                Proto => 'tcp',
                Listen => 1,
                Reuse => 1,
                );
die "Could not create socket: $!\n" unless $sock;
$new_sock = $sock->accept();
while ($incoming = <$new_sock>){
    print "hi";
        if ($incoming =~ m/.+/){
        print $incoming;
        @command = split / /,$incoming;
        $command[1] =~ s/\W+//g;
        $incoming = "";
        if ($command[0] eq "check"){
                $check = @check = `ps -ef |grep $command[1]`;
                print "$check\n@check\n";
                if ($check >= 12) {
                        print $new_sock "up";
                } else {
                        print $new_sock "down";
                }
        }else{
                print"did not work\n";
        }
    }
}
close $sock;

    [download]


    Likewise, the client works, so long as I don't duplicate the code to send a second request to the server.
    #!/usr/bin/perl
use strict;
use warnings;
use IO::Socket;
use Fcntl;

my $input;
my $sock;
my $cs2;
my $mqpcx;
my $mpts;
my $EOL = "\015\012";
my $BLANK = $EOL x 2;
my $command;

open OUT, "> testpage.html" or die "unable to write testpage";
### OUT is temporary until I get cgi working.
open FILE1, "< 1.html" or die;
while (<FILE1>){print OUT}
close FILE1;
$sock = new IO::Socket::INET (
        PeerAddr => '53.230.116.97',
        PeerPort => '8888',
        Proto => 'tcp',
        );
if ($sock){
    print "Connection established\n";
    $command = "check cs2" . $BLANK;
    print $sock $command;
    while ($cs2 = <$sock>){
        last if ($cs2 =~ m/.+/);
    }
    if ($cs2 eq "up") {
        print OUT "<img src=\"./cs2up.gif\">\n";
        $mpts++;
        print"so far, so good\n";
    } elsif ($cs2 eq "down") {
        print OUT "<img src=\"./cs2down.gif\">\n";
    } else {
        print "error getting data from other box";
    }
}else{
    print OUT "<img src=\"./cs2down.gif\">\n";
    print "no connection to other box";
}

close($sock);
close OUT;
print "goodbye\n";

    [download]

    --
    Believe nothing, no matter where you read it, or who said it - even if I have said it - unless it agrees with your own reason and your own common sense.
    (Buddha)
[reply]
[d/l]
[select]

      Well, if I look at the server, it goes:

      • Get a bunch of text from the client.
      • Run ps, etc
      • Send response to client.
      • Close client.

      Shouldn't that be:

      • While the client is still connected,
        • Get a command from the client.
        • Run ps, etc
        • Send response to client.
[reply]
        You beat me to my edit... Please recheck my previous post, just updated.

        --
        Believe nothing, no matter where you read it, or who said it - even if I have said it - unless it agrees with your own reason and your own common sense.
        (Buddha)
[reply]

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