Tcl

Send and Receive WebSocket Frame

See more WebSocket Examples

Demonstrates how to send a websocket text frame to a websocket echo server. This example uses Chilkat's websocket test echo server at ws://websockets.chilkat.io/wsChilkatEcho.ashx

Note: The websockets.chilkat.io server imposes the following limitations:
Messages must be 16K or less, and each connection is limited to a max of 16 echoed messages.

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.

set ws [new_CkWebSocket]

# For brevity, this example does not check for errors when etablishing the WebSocket connection.
# See Establish WebSocket Connection for more complete sample code for making the connection.

set rest [new_CkRest]

# Connect to websockets.chilkat.io
# IMPORTANT: websockets.chilkat.io accepts frames of up to 16K in size and echoes them back.
# IMPORTANT: The websockets.chilkat.io server imposes the following limitations: 
# ---------- Messages must be 16K or less, and each connection is limited to a max of 16 echoed messages.
set success [CkRest_Connect $rest "websockets.chilkat.io" 80 0 0]
CkWebSocket_UseConnection $ws $rest
CkWebSocket_AddClientHeaders $ws
set responseBodyIgnored [CkRest_fullRequestNoBody $rest "GET" "/wsChilkatEcho.ashx"]
set success [CkWebSocket_ValidateServerHandshake $ws]
if {$success != 1} then {
    puts [CkWebSocket_lastErrorText $ws]
    delete_CkWebSocket $ws
    delete_CkRest $rest
    exit
}

# This example demonstrates sending a frame and receiving a text frame.

# Send a frame containing the string "Hello World!"
# This will be the first and final frame, and therefore this constitutes the entire message.
set finalFrame 1
set success [CkWebSocket_SendFrame $ws "Hello World!" $finalFrame]
if {$success != 1} then {
    puts [CkWebSocket_lastErrorText $ws]
    delete_CkWebSocket $ws
    delete_CkRest $rest
    exit
}

# Read an incoming frame.
set success [CkWebSocket_ReadFrame $ws]
if {$success != 1} then {
    puts "Failed to receive a frame"
    puts "ReadFrame fail reason = [CkWebSocket_get_ReadFrameFailReason $ws]"
    puts [CkWebSocket_lastErrorText $ws]
    delete_CkWebSocket $ws
    delete_CkRest $rest
    exit
}

# Show the string that was received.
set receivedStr [CkWebSocket_getFrameData $ws]
puts "Received: $receivedStr"

# Close the websocket connection.
set success [CkWebSocket_SendClose $ws 1 1000 "Closing this websocket."]
if {$success != 1} then {
    puts [CkWebSocket_lastErrorText $ws]
    delete_CkWebSocket $ws
    delete_CkRest $rest
    exit
}

# Read the Close response.
set success [CkWebSocket_ReadFrame $ws]
if {$success != 1} then {
    puts "ReadFrame fail reason = [CkWebSocket_get_ReadFrameFailReason $ws]"
    puts [CkWebSocket_lastErrorText $ws]
    delete_CkWebSocket $ws
    delete_CkRest $rest
    exit
}

# Should receive the "Close" opcode.
puts "Received opcode: [CkWebSocket_frameOpcode $ws]"
# Should be the same status code we sent (1000)
puts "Received close status code: [CkWebSocket_get_CloseStatusCode $ws]"
# The server may echo the close reason.  If not, this will be empty.
puts "Echoed close reason: [CkWebSocket_closeReason $ws]"

puts "Success."

delete_CkWebSocket $ws
delete_CkRest $rest