IO::Socket and Term::Readline

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

Hi folks, I am trying to write an tcp server, which listens on a port and provides telnet clients a "command line". I love readline, but the readline prompt is getting displayed on the server side not to the client, not to mention the inpossibility to edit the line. does any of you have experience with this? I'm attaching the script, it's short and after running it you can telnet to localhost:8081

use IO::Socket;
use Term::ReadLine;
#####################################
# Server Script:
# Copyright 2003 (c) Philip Yuson
# this program is distributed according to
# the terms of the Perl license
# Use at your own risk
#####################################

$local = IO::Socket::INET->new(
                Proto     => 'tcp',             # protocol
                LocalAddr => 'localhost:8081',  # Host and port to lis
+ten to
                                                # Change the port if 8
+081 is being used
                Reuse     => 1
                ) or die "$!";

#####################################
# Server Script:
# Copyright 2003 (c) Philip Yuson
# this program is distributed according to
# the terms of the Perl license
# Use at your own risk
#####################################

$local = IO::Socket::INET->new(
                Proto     => 'tcp',             # protocol
                LocalAddr => 'localhost:8081',  # Host and port to lis
+ten to
                                                # Change the port if 8
+081 is being used
                Reuse     => 1
                ) or die "$!";

        $local->listen();       # listen
$local->autoflush(1);
# To send response immediately

print "At your service. Waiting...\n";
my $addr;       # Client handle
while ($addr = $local->accept() ) {
    # receive a request
        print   "Connected from: ", $addr->peerhost();  # Display mess
+ages
        print   " Port: ", $addr->peerport(), "\n";

    my $result;         # variable for Result
    #while (<$addr>) {  # Read all messages from client
        ## (Assume all valid numbers)
        #last if m/^end/gi;     # if message is 'end'
        ## then exit loop
        #print "Received: $_";  # Print received message
        #print $addr $_;                # Send received message back
        ## to verify
        #$result += $_;         # Add value to result
        #}
$term = new Term::ReadLine('Simple Perl calc');
$prompt = "Enter your arithmetic expression: ";
#$OUT = $term->OUT || STDOUT;

while ( defined ($_ = $term->readline($prompt)) )
{
$res = eval($_), "\n";
warn $@ if $@;
print $OUT $res, "\n" unless $@;
$term->addhistory($_) if /\S/;
}

    chomp;                      # Remove the <CR>

        if (m/^end/gi) {        # You need this. Otherwise if
                                # the client terminates abruptly
                                # The server will encounter an
                                # error when it sends the result back
                                # and terminate
                my $send = "result=$result";    # Format result messag
+e
                print $addr "$send\n";          # send the result mess
+age
                print "Result: $send\n";        # Display sent message
        }
        print "Closed connection\n";    # Inform that connection
                                        # to client is closed
        close $addr;    # close client
        print "At your service. Waiting...\n";  # Wait again for next 
+request
}
[download]

Comment on IO::Socket and Term::Readline Download Code

Replies are listed 'Best First'.
Re: IO::Socket and Term::Readline by pbeckingham (Parson) on Mar 13, 2004 at 18:14 UTC
The following line is using $OUT, which is not declared anywhere: `print $OUT $res, "\n" unless $@;` [download] The `\n` is ignored here, and that comma should probably be a concat operator: `$res = eval($_), "\n";` [download] Both of these were found by `use strict`, and the `-w` flag on the shebang. Please use it. The program then runs, or at least runs well enough to begin the real debugging.	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re: IO::Socket and Term::Readline
by pbeckingham (Parson) on Mar 13, 2004 at 18:14 UTC

The following line is using $OUT, which is not declared anywhere:

    print $OUT $res, "\n" unless $@;
[download]

The \n is ignored here, and that comma should probably be a concat operator:

    $res = eval($_), "\n";
[download]

Both of these were found by use strict, and the -w flag on the shebang. Please use it. The program then runs, or at least runs well enough to begin the real debugging.

[reply]
[d/l]
[select]