C

TCP Socket through SSH Tunnel (Port Forwarding)

See more Socket/SSL/TLS Examples

Demonstrates using Chilkat Socket to communicate to a TCP service through an SSH tunnel. This example will connect to an NIST time server and (using the old Time Protocol (RFC 868)), will read the current GMT time.

Note: This is not necessarily a recommended means for getting the current date/time. The most commonly used time protocol is the Network Time Protocol (RFC-1305). The intent of this example is to show how TCP communications can occur through an SSH tunnel.

C

#include <C_CkSocket.h>
#include <C_CkDateTime.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkSocket tunnel;
    const char *sshHostname;
    int sshPort;
    int maxWaitMs;
    BOOL useTls;
    HCkSocket channel;
    BOOL bigEndian;
    HCkDateTime dt;
    BOOL bLocalTime;

    success = FALSE;

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    tunnel = CkSocket_Create();

    sshHostname = "sftp.example.com";
    sshPort = 22;

    // Connect to an SSH server and establish the SSH tunnel:
    success = CkSocket_SshOpenTunnel(tunnel,sshHostname,sshPort);
    if (success == FALSE) {
        printf("%s\n",CkSocket_lastErrorText(tunnel));
        CkSocket_Dispose(tunnel);
        return;
    }

    // Authenticate with the SSH server via a login/password
    // or with a public key.
    // This example demonstrates SSH password authentication.
    success = CkSocket_SshAuthenticatePw(tunnel,"mySshLogin","mySshPassword");
    if (success == FALSE) {
        printf("%s\n",CkSocket_lastErrorText(tunnel));
        CkSocket_Dispose(tunnel);
        return;
    }

    // OK, the SSH tunnel is setup.  Now open a channel within the tunnel.
    // Once the channel is obtained, the Socket API may
    // be used exactly the same as usual, except all communications
    // are sent through the channel in the SSH tunnel.
    // Any number of channels may be created from the same SSH tunnel.
    // Multiple channels may coexist at the same time.

    // Connect to an NIST time server and read the current date/time
    maxWaitMs = 4000;
    useTls = FALSE;
    channel = CkSocket_Create();
    success = CkSocket_SshNewChannel(tunnel,"time-c.nist.gov",37,useTls,maxWaitMs,channel);
    if (success == FALSE) {
        printf("%s\n",CkSocket_lastErrorText(tunnel));
        CkSocket_Dispose(tunnel);
        CkSocket_Dispose(channel);
        return;
    }

    // The time server will send a big-endian 32-bit integer representing
    // the number of seconds since since 00:00 (midnight) 1 January 1900 GMT.
    // The ReceiveInt32 method will receive a 4-byte integer, but returns
    // TRUE or FALSE to indicate success.  If successful, the integer
    // is obtained via the ReceivedInt property.
    bigEndian = TRUE;
    success = CkSocket_ReceiveInt32(channel,bigEndian);
    if (success == FALSE) {
        printf("%s\n",CkSocket_lastErrorText(channel));
        CkSocket_Dispose(tunnel);
        CkSocket_Dispose(channel);
        return;
    }

    dt = CkDateTime_Create();
    CkDateTime_SetFromNtpTime(dt,CkSocket_getReceivedInt(channel));

    // Show the current local date/time
    bLocalTime = TRUE;
    printf("Current local date/time: %s\n",CkDateTime_getAsRfc822(dt,bLocalTime));

    // Close the SSH channel.
    success = CkSocket_Close(channel,maxWaitMs);
    if (success != TRUE) {
        printf("%s\n",CkSocket_lastErrorText(channel));
        CkSocket_Dispose(tunnel);
        CkSocket_Dispose(channel);
        CkDateTime_Dispose(dt);
        return;
    }

    // It is possible to create a new channel from the existing SSH tunnel for the next connection:
    // Any number of channels may be created from the same SSH tunnel.
    // Multiple channels may coexist at the same time.
    success = CkSocket_SshNewChannel(tunnel,"time-a.nist.gov",37,useTls,maxWaitMs,channel);
    if (success == FALSE) {
        printf("%s\n",CkSocket_lastErrorText(tunnel));
        CkSocket_Dispose(tunnel);
        CkSocket_Dispose(channel);
        CkDateTime_Dispose(dt);
        return;
    }

    // Review the LastErrorText to see that the connection was made via the SSH tunnel:
    printf("%s\n",CkSocket_lastErrorText(tunnel));

    // Close the connection to time-a.nist.gov.  This is actually closing our channel
    // within the SSH tunnel, but keeps the tunnel open for the next port-forwarded connection.
    success = CkSocket_Close(channel,maxWaitMs);
    if (success != TRUE) {
        printf("%s\n",CkSocket_lastErrorText(channel));
        CkSocket_Dispose(tunnel);
        CkSocket_Dispose(channel);
        CkDateTime_Dispose(dt);
        return;
    }

    // Finally, close the SSH tunnel.
    success = CkSocket_SshCloseTunnel(tunnel);
    if (success == FALSE) {
        printf("%s\n",CkSocket_lastErrorText(tunnel));
        CkSocket_Dispose(tunnel);
        CkSocket_Dispose(channel);
        CkDateTime_Dispose(dt);
        return;
    }

    printf("TCP SSH tunneling example completed.\n");


    CkSocket_Dispose(tunnel);
    CkSocket_Dispose(channel);
    CkDateTime_Dispose(dt);

    }