PHP

SSH Tunnel Static (Fixed-Destination) Port Forwarding

Demonstrates fixed-destination port forwarding with the DestHostname, DestPort, ListenBindIpAddress, and ListenPort properties. Every local connection accepted by the listener is forwarded to the same fixed destination through the SSH server.

Background: This is the classic ssh -L scenario: expose a single remote service — a database, an internal web app — at a local port. Binding the listener to 127.0.0.1 keeps the tunnel private to the local machine, whereas 0.0.0.0 would let other hosts route through it. Passing 0 to BeginAccepting lets the OS pick a free port, which ListenPort then reports — handy when a fixed port might already be in use.

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<?php

use Chilkat2\SshTunnel;

// Demonstrates fixed-destination (static) port forwarding with the SshTunnel properties
// DestHostname, DestPort, ListenBindIpAddress, and ListenPort.
//
// Every local connection accepted by the listener is forwarded to the same fixed destination
// through the SSH server.

$tunnel = new SshTunnel();

// The fixed destination that accepted connections are forwarded to.
$tunnel->DestHostname = 'db.internal.example.com';
$tunnel->DestPort = 5432;

// Bind the listener to loopback so only local processes can use the tunnel.  Use "0.0.0.0" to
// accept connections from other machines (less secure).
$tunnel->ListenBindIpAddress = '127.0.0.1';

$sshPort = 22;
try {
    $tunnel->Connect('ssh.example.com', $sshPort);

    // 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.
    $password = 'mySshPassword';

    $tunnel->AuthenticatePw('mySshLogin', $password);

    // Pass 0 to let the operating system choose an available port.  After BeginAccepting succeeds,
    // ListenPort contains the actual port that was bound.
    $tunnel->BeginAccepting(0);
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

echo 'Listening on 127.0.0.1 port ', $tunnel->ListenPort, "\n";

// Applications now connect to 127.0.0.1:ListenPort as if it were the database server.

$waitForThreadExit = true;
try {
    $tunnel->CloseTunnel($waitForThreadExit);
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}