(Visual FoxPro) WebSocket through SSH Tunnel

This example shows how to establish a WebSocket connection through an SSH tunnel. The WebSocket protocol communications will be encapsulated within an SSH tunnel.

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LOCAL loTunnel
LOCAL lcSshHostname
LOCAL lnSshPort
LOCAL lnSuccess
LOCAL loChannel
LOCAL lnBTls
LOCAL lnPort
LOCAL lnMaxWaitMs
LOCAL loRest
LOCAL loWs
LOCAL lcResponseBody
LOCAL lnStatusCode

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

* --------------------------------------------------
* This example borrows the code from the REST through SSH Tunnel example.
* We first use the Chilkat Socket object to establish a connection to the WebSocket server through an SSH Tunnel.
* Next, the Rest object uses the Socket object for its connection.
* Finally, the WebSocket object uses the Rest object for its connection.  
* 
* Hopefully the flexibility of this architecture is easy to see.  All of the HTTP functionality of the Rest object,
* such as HTTP authentication, custom headers, etc. is available to the WebSocket.  Likewise, all of the advanced functionality
* of the Socket object is in turn available to the Rest object.  

* The high-level steps for accomplishing the task of running the WebSocket protocol through an SSH accomplished as follows:
* 1) Create the SSH tunnel using Chilkat Socket.
* 2) Open a port-forwarding channel (to the WebSocket server) within the tunnel.
* 2) Tell Rest to use the Socket object.
* 3) Tell WebSocket to use the Rest object.

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Socket')
loTunnel = CreateObject('Chilkat.Socket')

lcSshHostname = "sftp.example.com"
lnSshPort = 22

* Connect to an SSH server and establish the SSH tunnel:
lnSuccess = loTunnel.SshOpenTunnel(lcSshHostname,lnSshPort)
IF (lnSuccess <> 1) THEN
    ? loTunnel.LastErrorText
    RELEASE loTunnel
    CANCEL
ENDIF

* Authenticate with the SSH server via a login/password
* or with a public key.
* This example demonstrates SSH password authentication.
lnSuccess = loTunnel.SshAuthenticatePw("mySshLogin","mySshPassword")
IF (lnSuccess <> 1) THEN
    ? loTunnel.LastErrorText
    RELEASE loTunnel
    CANCEL
ENDIF

*  OK, the SSH tunnel is setup.  Now open a channel within the tunnel.

lnBTls = 1
lnPort = 443
lnMaxWaitMs = 5000

* This returns a socket object that is a single channel within the SSH tunnel.
* The SSH channel is our logical port-forwarded connection through the SSH tunnel.
* Note: This example establishes a TLS connection to the target WebSocket server.
* (The TLS protocol will run on the logical channel within the SSH tunnel.)
* Your application can just as easily make a non-TLS connection by changing the arguments
* passed to SshOpenChannel.
loChannel = loTunnel.SshOpenChannel("some-websocket-server.com",lnPort,lnBTls,lnMaxWaitMs)
IF (loTunnel.LastMethodSuccess <> 1) THEN
    ? loTunnel.LastErrorText
    RELEASE loTunnel
    CANCEL
ENDIF

* Create a REST object and tell it to use the SSH channel.
* This connection is a TLS running on an SSH channel through an SSH tunnel.
* In other words, TLS is wrapped within the SSH tunnel.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Rest')
loRest = CreateObject('Chilkat.Rest')
lnSuccess = loRest.UseConnection(loChannel,0)
IF (lnSuccess <> 1) THEN
    ? loRest.LastErrorText
    RELEASE loChannel
    RELEASE loTunnel
    RELEASE loRest
    CANCEL
ENDIF

* Finally, tell our WebSocket object to use the Rest object..
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.WebSocket')
loWs = CreateObject('Chilkat.WebSocket')

* Tell the WebSocket to use this connection.
lnSuccess = loWs.UseConnection(loRest)
IF (lnSuccess <> 1) THEN
    ? loWs.LastErrorText
    RELEASE loTunnel
    RELEASE loRest
    RELEASE loWs
    CANCEL
ENDIF

* Add the standard WebSocket open handshake headers that will be needed.
* (This adds the required HTTP request headers to the rest object.)
loWs.AddClientHeaders()

* Add any additional headers that might be desired.
* Two common WebSocketSpecific headers are "Sec-WebSocket-Protocol" and "Origin".
loRest.AddHeader("Sec-WebSocket-Protocol","x-some-websocket-subprotocol")
loRest.AddHeader("Origin","http://some-websocket-server.com")

* Do the open handshake.
lcResponseBody = loRest.FullRequestNoBody("GET","/something")
IF (loRest.LastMethodSuccess <> 1) THEN
    ? loRest.LastErrorText
    RELEASE loTunnel
    RELEASE loRest
    RELEASE loWs
    CANCEL
ENDIF

* If successful, the HTTP response status code should be 101,
* and the response body will be empty. (If it failed, we'll have a look
* at the response body..)
lnStatusCode = loRest.ResponseStatusCode
? "Response status code: " + STR(lnStatusCode)

IF (lnStatusCode <> 101) THEN
    ? lcResponseBody
    ? "-- Failed because of unexpected response status code."
    RELEASE loTunnel
    RELEASE loRest
    RELEASE loWs
    CANCEL
ENDIF

* We have the expected 101 response, so let's now validate the 
* contents of the response, such as the value sent by the server in the
* Sec-WebSocket-Accept header. 
lnSuccess = loWs.ValidateServerHandshake()
IF (lnSuccess <> 1) THEN
    ? loWs.LastErrorText
    RELEASE loTunnel
    RELEASE loRest
    RELEASE loWs
    CANCEL
ENDIF

? "WebSocket connection successful."

* The application may now begin sending and receiving frames on the WebSocket connection.
* (At this point, we're done with the rest object...)

RELEASE loTunnel
RELEASE loRest
RELEASE loWs