B4X Requires Chilkat v11.0.0+

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. B4X

Dim success As Boolean = False

'  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.

Dim tunnel As ChilkatSocket
tunnel.Initialize("tunnel")

Dim sshHostname As String = "sftp.example.com"
Dim sshPort As Int = 22

'  Connect to an SSH server and establish the SSH tunnel:
success = tunnel.SshOpenTunnel(sshHostname, sshPort)
If success = False Then
    Log(tunnel.LastErrorText)
    Return
End If


'  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 Then
    Log(tunnel.LastErrorText)
    Return
End If


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

Dim bTls As Boolean = True
Dim port As Int = 443
Dim maxWaitMs As Int = 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.
Dim channel As ChilkatSocket
channel.Initialize("channel")
success = tunnel.SshNewChannel("some-websocket-server.com", port, bTls, maxWaitMs, channel)
If success = False Then
    Log(tunnel.LastErrorText)
    Return
End If


'  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.
Dim rest As ChilkatRest
rest.Initialize("rest")
success = rest.UseConnection(channel, False)
If success = False Then
    Log(rest.LastErrorText)
    Return
End If


'  Finally, tell our WebSocket object to use the Rest object..
Dim ws As ChilkatWebSocket
ws.Initialize("ws")

'  Tell the WebSocket to use this connection.
success = ws.UseConnection(rest)
If success = False Then
    Log(ws.LastErrorText)
    Return
End If


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

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

'  Do the open handshake.
Dim responseBody As String = rest.FullRequestNoBody("GET", "/something")
If rest.LastMethodSuccess = False Then
    Log(rest.LastErrorText)
    Return
End If


'  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..)
Dim statusCode As Int = rest.ResponseStatusCode
Log("Response status code: " & statusCode)

If statusCode <> 101 Then
    Log(responseBody)
    Log("-- Failed because of unexpected response status code.")
    Return
End If


'  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. 
success = ws.ValidateServerHandshake
If success = False Then
    Log(ws.LastErrorText)
    Return
End If


Log("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...)