Lua

Send and Receive WebSocket Messages

See more WebSocket Examples

This example how to send and receive websocket messages.

A WebSocket message can be composed of one or more frames. The simple case is where a single frame is both the first and last frame in a message. This is the case where the 1st frame in the message has the "final frame" bit set.

This example demonstrates sending and receiving multi-frame messages.

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.

Lua

local chilkat = require("chilkat")

-- This example requires the Chilkat API to have been previously unlocked.
-- See Global Unlock Sample for sample code.

local ws = chilkat.WebSocket.new()

-- 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.

local rest = chilkat.Rest.new()
-- 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.
local success = rest:connect("websockets.chilkat.io", 80, false, false)
ws:use_connection(rest)
ws:add_client_headers()
local responseBodyIgnored = rest:full_request_no_body("GET", "/wsChilkatEcho.ashx")
success = ws:validate_server_handshake()
if not success then
    print(ws.last_error_text)
    return
end

-- This example demonstrates sending and receiving a multi-frame message.

-- The websocket message will be composed of three text lines, each frame will contain a single line.

-- Send the 1st frame in the message.
local finalFrame = false
success = ws:send_frame("This is the 1st frame\r\n", finalFrame)
if not success then
    print(ws.last_error_text)
    return
end

-- Send the 2nd frame in the message.
success = ws:send_frame("This is the 2nd frame\r\n", finalFrame)
if not success then
    print(ws.last_error_text)
    return
end

-- Send the 3rd and final frame in the message.
finalFrame = true
success = ws:send_frame("This is the 3rd frame\r\n", finalFrame)
if not success then
    print(ws.last_error_text)
    return
end

-- Read an incoming frames until we receive the final frame.
-- Note: It may be that the echo server (websockets.chilkat.io) responds with
-- the full message in a single final frame.
local receivedFinalFrame = false
while not receivedFinalFrame do
    success = ws:read_frame()
    if not success then
        print("Failed to receive a frame")
        print("ReadFrame fail reason = " .. ws.read_frame_fail_reason)
        print(ws.last_error_text)
        return
    end

    receivedFinalFrame = ws.final_frame

    -- Show the opcode and final frame bit for the frame just received:
    print("Frame opcode: " .. ws.frame_opcode)
    print("Final frame: " .. tostring(receivedFinalFrame))
end

-- Return the message accumulated in the above calls to ReadFrame.
local receivedMsg = ws:get_frame_data()
print("Received: " .. receivedMsg)

-- Close the websocket connection.
success = ws:send_close(true, 1000, "Closing this websocket.")
if not success then
    print(ws.last_error_text)
    return
end

-- Read the Close response.
success = ws:read_frame()
if not success then
    print("ReadFrame fail reason = " .. ws.read_frame_fail_reason)
    print(ws.last_error_text)
    return
end

-- Should receive the "Close" opcode.
print("Received opcode: " .. ws.frame_opcode)
-- Should be the same status code we sent (1000)
print("Received close status code: " .. ws.close_status_code)
-- The server may echo the close reason.  If not, this will be empty.
print("Echoed close reason: " .. ws.close_reason)

print("Success.")