Tcl

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. Tcl

load ./chilkat.dll

set success 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.

set tunnel [new_CkSocket]

set sshHostname "sftp.example.com"
set sshPort 22

# Connect to an SSH server and establish the SSH tunnel:
set success [CkSocket_SshOpenTunnel $tunnel $sshHostname $sshPort]
if {$success == 0} then {
    puts [CkSocket_lastErrorText $tunnel]
    delete_CkSocket $tunnel
    exit
}

# Authenticate with the SSH server via a login/password
# or with a public key.
# This example demonstrates SSH password authentication.
set success [CkSocket_SshAuthenticatePw $tunnel "mySshLogin" "mySshPassword"]
if {$success == 0} then {
    puts [CkSocket_lastErrorText $tunnel]
    delete_CkSocket $tunnel
    exit
}

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

set bTls 1
set port 443
set maxWaitMs 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.
set channel [new_CkSocket]

set success [CkSocket_SshNewChannel $tunnel "some-websocket-server.com" $port $bTls $maxWaitMs $channel]
if {$success == 0} then {
    puts [CkSocket_lastErrorText $tunnel]
    delete_CkSocket $tunnel
    delete_CkSocket $channel
    exit
}

# 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.
set rest [new_CkRest]

set success [CkRest_UseConnection $rest $channel 0]
if {$success == 0} then {
    puts [CkRest_lastErrorText $rest]
    delete_CkSocket $tunnel
    delete_CkSocket $channel
    delete_CkRest $rest
    exit
}

# Finally, tell our WebSocket object to use the Rest object..
set ws [new_CkWebSocket]

# Tell the WebSocket to use this connection.
set success [CkWebSocket_UseConnection $ws $rest]
if {$success == 0} then {
    puts [CkWebSocket_lastErrorText $ws]
    delete_CkSocket $tunnel
    delete_CkSocket $channel
    delete_CkRest $rest
    delete_CkWebSocket $ws
    exit
}

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

# Add any additional headers that might be desired.
# Two common WebSocketSpecific headers are "Sec-WebSocket-Protocol" and "Origin".
CkRest_AddHeader $rest "Sec-WebSocket-Protocol" "x-some-websocket-subprotocol"
CkRest_AddHeader $rest "Origin" "http://some-websocket-server.com"

# Do the open handshake.
set responseBody [CkRest_fullRequestNoBody $rest "GET" "/something"]
if {[CkRest_get_LastMethodSuccess $rest] == 0} then {
    puts [CkRest_lastErrorText $rest]
    delete_CkSocket $tunnel
    delete_CkSocket $channel
    delete_CkRest $rest
    delete_CkWebSocket $ws
    exit
}

# 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..)
set statusCode [CkRest_get_ResponseStatusCode $rest]
puts "Response status code: $statusCode"

if {$statusCode != 101} then {
    puts "$responseBody"
    puts "-- Failed because of unexpected response status code."
    delete_CkSocket $tunnel
    delete_CkSocket $channel
    delete_CkRest $rest
    delete_CkWebSocket $ws
    exit
}

# 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. 
set success [CkWebSocket_ValidateServerHandshake $ws]
if {$success == 0} then {
    puts [CkWebSocket_lastErrorText $ws]
    delete_CkSocket $tunnel
    delete_CkSocket $channel
    delete_CkRest $rest
    delete_CkWebSocket $ws
    exit
}

puts "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...)

delete_CkSocket $tunnel
delete_CkSocket $channel
delete_CkRest $rest
delete_CkWebSocket $ws