Common Perl Net:: Applications
Perl Net:: is one of the standard methods for IP application interface in Perl. It is more fully documented in the
book - Network Programming with Perl by Lincoln B. Stein.
Telnet
Telnet (Telecommunication network) is used for command line access to a remote system - UNIX, Windows,
router, switch etc - to execute system commands remotely on that system. Because of security issues with
Telnet (like no encryption), use of SSH has increased for remote access.
Telnet can open interactive raw-TCP sessions on any port for diagnosing network problems or manually "talk"
to other services as a simple way to send commands to the server and examine the responses. Other software
such as nc (netcat) on Unix (or PuTTY on Windows) are increasingly used for this as they can be called with
arguments not to send any terminal control handshaking data unlike standard Telnet client software
.
You can run telnet without parameters in order to enter the telnet command prompt (telnet>). From the Telnet
prompt, use the following commands to manage a computer running Telnet Client.
Telnet commands:
telnet [RemoteServer] [port#]
Without parameters, telnet provides a Telnet Client prompt:
Telnet prompt commands:
quit or q.
open or o [RemoteServer] [Port] Default port 23 is assumed.
close or c [RemoteServer]
.set [RemoteServer] [ntlm] [localecho] [term {ansi | vt100 | vt52 | vtnt}] [escape Character] [logfile FileName] [logging]
[bsasdel] [crlf] [delasbs] [mode {console | stream}] [?]
unset [Option]: To turn off an option that was previously set
To send Telnet Client commands
send [RemoteServer] [ao: Abort] [ayt: "Are you there?" ] [esc] [ip: Interrupts the process] [synch] [?]
Display: To view the current settings for the Telnet client
Net::Telnet
The new() method creates a new Net::Telnet object with a single argument containing the name of the host to
connect to, or with a series of option/value pairs that provide finer control over the session:
$telnet = Net::Telnet->new($host)
$telnet = Net::Telnet->new(Option1=>$value1,Option2=>$value2 ..)
Add’l Options: Host, Port (default 23), Timeout (10 seconds), Binmode (Suppress CRLF translation-
true/false), Cmd_remove_mode, Errmode ("die"), Input_log, Fhopen, Prompt (/[\$%#>] $/)
Exercise160 (Telnet example):
#!/usr/bin/perl
use strict;
use Net::Telnet;
use constant HOST => '("63.164.54.114)';
use constant USER => 'testuser';
use constant PASS => 'testuser;
my $telnet = Net::Telnet->new(HOST);
$telnet->login(USER,PASS);
my @lines = $telnet->cmd('ps -ef');
print @lines;
