Visual FoxPro

WebSocket through SSH Tunnel

See more WebSocket Examples

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

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

lnSuccess = 0

* 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.

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 = 0) 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 = 0) 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 SshNewChannel.
loChannel = CreateObject('Chilkat.Socket')
lnSuccess = loTunnel.SshNewChannel("some-websocket-server.com",lnPort,lnBTls,lnMaxWaitMs,loChannel)
IF (lnSuccess = 0) THEN
    ? loTunnel.LastErrorText
    RELEASE loTunnel
    RELEASE loChannel
    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.
loRest = CreateObject('Chilkat.Rest')
lnSuccess = loRest.UseConnection(loChannel,0)
IF (lnSuccess = 0) THEN
    ? loRest.LastErrorText
    RELEASE loTunnel
    RELEASE loChannel
    RELEASE loRest
    CANCEL
ENDIF

* Finally, tell our WebSocket object to use the Rest object..
loWs = CreateObject('Chilkat.WebSocket')

* Tell the WebSocket to use this connection.
lnSuccess = loWs.UseConnection(loRest)
IF (lnSuccess = 0) THEN
    ? loWs.LastErrorText
    RELEASE loTunnel
    RELEASE loChannel
    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 = 0) THEN
    ? loRest.LastErrorText
    RELEASE loTunnel
    RELEASE loChannel
    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 loChannel
    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 = 0) THEN
    ? loWs.LastErrorText
    RELEASE loTunnel
    RELEASE loChannel
    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 loChannel
RELEASE loRest
RELEASE loWs