C++

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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C++

#include <CkSsh.h>

void ChilkatSample(void)
    {
    bool success = false;

    //  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.

    CkSsh ssh;

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

    //  The target name is resolved by the SSH server, not by this computer, so it must be
    //  reachable from the server's network.
    const char *targetHostname = "db.internal.example.com";
    int targetPort = 5432;
    int channelNum = ssh.OpenDirectTcpIpChannel(targetHostname,targetPort);
    if (channelNum < 0) {
        std::cout << ssh.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "Opened direct-tcpip channel: " << channelNum << "\r\n";

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

    ssh.Disconnect();
    }