(JavaScript) TCP Socket through SSH Tunnel (Port Forwarding)

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.

Note: This example requires Chilkat v11.0.0 or greater.

Note

This example is intended for running within a Chilkat.Js embedded JavaScript engine. All Chilkat JavaScript examples require Chilkat v11.4.0 or greater.

var success = false;

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

var tunnel = new CkSocket();

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

// Connect to an SSH server and establish the SSH tunnel:
success = tunnel.SshOpenTunnel(sshHostname,sshPort);
if (success == false) {
    console.log(tunnel.LastErrorText);
    return;
}

// Authenticate with the SSH server via a login/password
// or with a public key.
// This example demonstrates SSH password authentication.
success = tunnel.SshAuthenticatePw("mySshLogin","mySshPassword");
if (success == false) {
    console.log(tunnel.LastErrorText);
    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
var maxWaitMs = 4000;
var useTls = false;
var channel = new CkSocket();
success = tunnel.SshNewChannel("time-c.nist.gov",37,useTls,maxWaitMs,channel);
if (success == false) {
    console.log(tunnel.LastErrorText);
    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.
var bigEndian = true;
success = channel.ReceiveInt32(bigEndian);
if (success == false) {
    console.log(channel.LastErrorText);
    return;
}

var dt = new CkDateTime();
dt.SetFromNtpTime(channel.ReceivedInt);

// Show the current local date/time
var bLocalTime = true;
console.log("Current local date/time: " + dt.GetAsRfc822(bLocalTime));

// Close the SSH channel.
success = channel.Close(maxWaitMs);
if (success !== true) {
    console.log(channel.LastErrorText);
    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 = tunnel.SshNewChannel("time-a.nist.gov",37,useTls,maxWaitMs,channel);
if (success == false) {
    console.log(tunnel.LastErrorText);
    return;
}

// Review the LastErrorText to see that the connection was made via the SSH tunnel:
console.log(tunnel.LastErrorText);

// 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 = channel.Close(maxWaitMs);
if (success !== true) {
    console.log(channel.LastErrorText);
    return;
}

// Finally, close the SSH tunnel.
success = tunnel.SshCloseTunnel();
if (success == false) {
    console.log(tunnel.LastErrorText);
    return;
}

console.log("TCP SSH tunneling example completed.");