Open a direct-tcpip Channel (SSH Port Forwarding)

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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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    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.

    ssh := chilkat.NewSsh()

    sshPort := 22
    success = ssh.Connect("ssh.example.com",sshPort)
    if success == false {
        fmt.Println(ssh.LastErrorText())
        ssh.DisposeSsh()
        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.
    password := "mySshPassword"

    success = ssh.AuthenticatePw("mySshLogin",password)
    if success == false {
        fmt.Println(ssh.LastErrorText())
        ssh.DisposeSsh()
        return
    }

    //  The target name is resolved by the SSH server, not by this computer, so it must be
    //  reachable from the server's network.
    targetHostname := "db.internal.example.com"
    targetPort := 5432
    channelNum := ssh.OpenDirectTcpIpChannel(targetHostname,targetPort)
    if channelNum < 0 {
        fmt.Println(ssh.LastErrorText())
        ssh.DisposeSsh()
        return
    }

    fmt.Println("Opened direct-tcpip channel: ", channelNum)

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

    ssh.Disconnect()

    ssh.DisposeSsh()