Perl

Open a direct-tcpip Channel (SSH Port Forwarding)

Demonstrates the Chilkat Ssh.OpenDirectTcpIpChannel method, which opens a direct-tcpip channel through the SSH server to a target host and port. The first argument is the target hostname and the second is the target port. It returns the channel number, or -1 on failure.

Background: This is SSH local port forwarding at the API level: the channel carries ordinary TCP traffic to a service that may be reachable only from the SSH server's network — a database, an internal web app, a message broker. The key detail is that the server resolves the target name, not your machine, so it must resolve and be reachable there. Supplying a numeric IPv4 address avoids remote DNS resolution entirely.

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use strict;
use warnings;
use Chilkat2;

# Demonstrates the Ssh.OpenDirectTcpIpChannel method, which opens a direct-tcpip channel
# through the SSH server to a target host and port.  The 1st argument is the target hostname
# and the 2nd is the target port.  It returns the channel number, or -1 on failure.

my $ssh = Chilkat2::Ssh->new;

my $sshPort = 22;
my $success = $ssh->Connect('ssh.example.com', $sshPort);
if (!$success) {
    print $ssh->LastErrorText, "\n";
    exit;
}

# Normally you would not hard-code the password in source.  You should instead obtain it
# from an interactive prompt, environment variable, or a secrets vault.
my $password = 'mySshPassword';

$success = $ssh->AuthenticatePw('mySshLogin', $password);
if (!$success) {
    print $ssh->LastErrorText, "\n";
    exit;
}

# The target name is resolved by the SSH server, not by this computer, so it must be
# reachable from the server's network.
my $targetHostname = 'db.internal.example.com';
my $targetPort = 5432;
my $channelNum = $ssh->OpenDirectTcpIpChannel($targetHostname, $targetPort);
if ($channelNum < 0) {
    print $ssh->LastErrorText, "\n";
    exit;
}

print 'Opened direct-tcpip channel: ', $channelNum, "\n";

# The channel now carries ordinary TCP data to the target, tunneled over SSH.

$ssh->Disconnect();