Unicode 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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Unicode C

#include <C_CkSshW.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkSshW ssh;
    int sshPort;
    const wchar_t *password;
    const wchar_t *targetHostname;
    int targetPort;
    int channelNum;

    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 = CkSshW_Create();

    sshPort = 22;
    success = CkSshW_Connect(ssh,L"ssh.example.com",sshPort);
    if (success == FALSE) {
        wprintf(L"%s\n",CkSshW_lastErrorText(ssh));
        CkSshW_Dispose(ssh);
        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 = L"mySshPassword";

    success = CkSshW_AuthenticatePw(ssh,L"mySshLogin",password);
    if (success == FALSE) {
        wprintf(L"%s\n",CkSshW_lastErrorText(ssh));
        CkSshW_Dispose(ssh);
        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 = L"db.internal.example.com";
    targetPort = 5432;
    channelNum = CkSshW_OpenDirectTcpIpChannel(ssh,targetHostname,targetPort);
    if (channelNum < 0) {
        wprintf(L"%s\n",CkSshW_lastErrorText(ssh));
        CkSshW_Dispose(ssh);
        return;
    }

    wprintf(L"Opened direct-tcpip channel: %d\n",channelNum);

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

    CkSshW_Disconnect(ssh);


    CkSshW_Dispose(ssh);

    }