C++

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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C++

#include <CkSshTunnel.h>

void ChilkatSample(void)
    {
    bool success = false;

    //  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.

    CkSshTunnel tunnel;

    //  The fixed destination that accepted connections are forwarded to.
    tunnel.put_DestHostname("db.internal.example.com");
    tunnel.put_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.put_ListenBindIpAddress("127.0.0.1");

    int sshPort = 22;
    success = tunnel.Connect("ssh.example.com",sshPort);
    if (success == false) {
        std::cout << tunnel.lastErrorText() << "\r\n";
        return;
    }

    //  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.
    const char *password = "mySshPassword";

    success = tunnel.AuthenticatePw("mySshLogin",password);
    if (success == false) {
        std::cout << tunnel.lastErrorText() << "\r\n";
        return;
    }

    //  Pass 0 to let the operating system choose an available port.  After BeginAccepting succeeds,
    //  ListenPort contains the actual port that was bound.
    success = tunnel.BeginAccepting(0);
    if (success == false) {
        std::cout << tunnel.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "Listening on 127.0.0.1 port " << tunnel.get_ListenPort() << "\r\n";

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

    bool waitForThreadExit = true;
    success = tunnel.CloseTunnel(waitForThreadExit);
    if (success == false) {
        std::cout << tunnel.lastErrorText() << "\r\n";
        return;
    }
    }