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

i have a client/server tcp socket script that works but i would like to send stdout from server back to client. for example i send ls /tmp to server i would like to see the ls output on the client. any help would be great

Client code:

    

#!/usr/bin/env perl 
 
use IO::Socket; 
use strict; 
 
my $socket = new IO::Socket::INET ( 
                                  PeerAddr => $_, 
                                  PeerPort => '7071', 
                                  Proto => 'tcp', 
                               ); 
 
die "Coudn't open socket" unless $socket; 
 
$socket->autoflush(1); 
 
my $dir = "/tmp"; 
 
print $socket "ls:$dir\n"; 
 
close($socket);

[download]

server code:

        

#!/usr/bin/env perl  
 
# perl modules 
use IO::Socket; 
use POSIX qw(:sys_wait_h); 
use Sys::Hostname; 
 
my $hostname = hostname; 
 
my $port = "7071"; 
 
$SIG{CHLD} = 'IGNORE'; 
 
# make socket connection 
my $socket = new IO::Socket::INET ( 
        LocalHost => "$hostname", 
        LocalPort => "$port", 
        Proto => 'tcp', 
        Reuse => 1, 
        Listen => SOMAXCONN, 
); die "Could not create socket: $!\n" unless $socket; 
 
while ($client = $socket->accept()) { 
 
        $client->autoflush(1); 
 
        while (<$client>) { 
                chomp; 
 
                my ($command,@var2) = split(":", $_); 
                my $cmd; 
 
                $pid = fork; 
                if ($pid == 0){ 
                } else { 
                                `kill $pid 2>/dev/null`; 
                } 
 
                unless ( $pid ){ 
 
                        if ($command eq 'ls'){ 
                                $cmd = sprintf("ls -s @var"); 
                        }  
 
                        $run_cmd = system($cmd); 
 
        } 
        } 
 
        close($client); 
 
} 
 
close($socket);

[download]

Replies are listed 'Best First'.
Re: socket help
by ikegami (Patriarch) on Feb 14, 2011 at 02:44 UTC 
    use IPC::Open3 qw( open3 );

while (my $client = $socket->accept()) { 
   while (<$client>) { 
      chomp; 
      my ($cmd, @args) = split(/:/, $_); 

      my @cmd;
      if ($cmd eq 'ls') {
         @cmd = ( 'ls', '-s', '--', @args );
      }

      if (@cmd) {
         open(local *C_STDIN,  '<', '/dev/null') or die;
         open(local *C_STDOUT, '>&, $client) or die;
         my $pid = open3('<C_STDIN', '>C_STDOUT', '>C_STDOUT', @cmd);
         waitpid($pid, 0);
      }
   }
}

    [download]
[reply]
[d/l]
      I tried the suggestion and still got nothing back.
      client code: 
      #!/usr/bin/env perl

use IO::Socket;
$remote_port=7071;
$remote_host="localhost ";
$socket = IO::Socket::INET->new(PeerAddr => $remote_host,
                                PeerPort => $remote_port,
                                Proto    => "tcp",
                                Type     => SOCK_STREAM)
    or die "Couldn't connect to $remote_host:$remote_port : $@\n";

$socket->autoflush(1);

# ... do something with the socket
print $socket "ls:/tmp\n";

while (<$socket>) {
        print "$_\n";
}

# and terminate the connection when we're done
close($socket);

      [download]

      Server code: 
      #!/usr/bin/env perl

# perl modules
use IO::Socket;
use POSIX qw(:sys_wait_h);
use Sys::Hostname;
use IPC::Open3 qw( open3 );

# get hostname
my $hostname = hostname;

# Port
my $port = "7071";

$SIG{CHLD} = 'IGNORE';

# make socket connection
my $socket = new IO::Socket::INET (
        LocalHost => "$hostname",
        LocalPort => "$port",
        Proto => 'tcp',
        Reuse => 1,
        Listen => SOMAXCONN,
); die "Could not create socket: $!\n" unless $socket;

# allow server to accept clients
while ($client = $socket->accept()) {

        # flush input
        $client->autoflush(1);

        # input from client
        while (<$client>) {
                chomp;

                # read command and put rest in array
                my ($command,@var2) = split(":", $_);
                my $cmd;

                        if ($command eq 'ls'){
                                @cmd = ( 'ls', '-s', '--', @var2 );
                        }

                        # run command
                        if (@cmd) {
                                open(local *C_STDIN, '<', '/dev/null')
+ or die;
                                open(local *C_STDIN, '>&', $client) or
+ die;
                                my $pid = open3('C_STDIN', '>C_STDOUT'
+, 'C_STDOUT', @cmd);
                                waitpid($pid, 0);
                        }
        }

        # close client
        close($client);

        
}

# close socket so it can reused
close($socket);

      [download]
[reply]
[d/l]
[select]
        That's not the code I posted at all, and you're hiding potential error messages by not using use strict; use warnings;.
[reply]
[d/l]
Re: socket help
by snoopy (Curate) on Feb 14, 2011 at 02:30 UTC
    The implicit use of global $_ in the client code seems a bit odd. This variable is not set explicitly from the command line without careful invocation: 
    echo myarg | perl -nle 'print "ARG=<$_>\n"'
ARG=<myarg>

    [download]

    You're better off, at least, fetching from ARGV: 

    my ($hostname) = @ARGV;
die "usage: $0 hostname" unless $hostname;
my $socket = new IO::Socket::INET ( 
                                  PeerAddr => $hostname, 
                                  PeerPort => '7071', 
                                  Proto => 'tcp', 
                               );

    [download]
    ...or however you want to parse the command line arguments in @ARGV.
[reply]
[d/l]
[select]
      $_ is supposed to be $ARGV[0]. 
      PeerAddr => $ARGV[0],

      [download]
      I've also tried using backticks 
      chomp(my $output = `ls /tmp 2>&1`);

      [download]
      It's like the client isn't waiting for the server to finish
[reply]
[d/l]
[select]
Re: socket help
by Anonymous Monk on Feb 14, 2011 at 00:44 UTC
    use backticks/qx instead of system to capture the output of ls, then print it back to the client
[reply]
      i've tried using backticks and still get nothing. I also just tried sending the output from the server to a file and having the client read the file. This would work as long as the client didn't have to wait for the server. The client would not wait for the server to finish before it read the file.
[reply]
        i've tried using backticks and still get nothing.

        Show what you tried

[reply]

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