(Lianja) 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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//  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("CkSocket")

lcSshHostname = "www.my-ssh-server.com"
lnSshPort = 22

//  Connect to an SSH server and establish the SSH tunnel:
llSuccess = loTunnel.SshOpenTunnel(lcSshHostname,lnSshPort)
if (llSuccess <> .T.) then
    ? loTunnel.LastErrorText
    release loTunnel
    return
endif

//  Authenticate with the SSH server via a login/password
//  or with a public key.
//  This example demonstrates SSH password authentication.
llSuccess = loTunnel.SshAuthenticatePw("mySshLogin","mySshPassword")
if (llSuccess <> .T.) then
    ? loTunnel.LastErrorText
    release loTunnel
    return
endif

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

llBTls = .T.
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,llBTls,lnMaxWaitMs)
if (loTunnel.LastMethodSuccess <> .T.) then
    ? loTunnel.LastErrorText
    release loTunnel
    return
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("CkRest")
llSuccess = loRest.UseConnection(loChannel,.F.)
if (llSuccess <> .T.) then
    ? loRest.LastErrorText
    release loChannel
    release loTunnel
    release loRest
    return
endif

//  Finally, tell our WebSocket object to use the Rest object..
loWs = createobject("CkWebSocket")

//  Tell the WebSocket to use this connection.
llSuccess = loWs.UseConnection(loRest)
if (llSuccess <> .T.) then
    ? loWs.LastErrorText
    release loTunnel
    release loRest
    release loWs
    return
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 <> .T.) then
    ? loRest.LastErrorText
    release loTunnel
    release loRest
    release loWs
    return
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
    return
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.
llSuccess = loWs.ValidateServerHandshake()
if (llSuccess <> .T.) then
    ? loWs.LastErrorText
    release loTunnel
    release loRest
    release loWs
    return
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