Lua

WebSocket Send/Receive Binary Data

See more WebSocket Examples

Demonstrates how to send and receive binary data on a websocket. 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.

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 sends a small JPG file (about 7KB) in a websocket frame.
local jpgData = chilkat.BinData.new()
success = jpgData:load_file("qa_data/jpg/starfish.jpg")

print("Number of bytes to send = " .. jpgData.num_bytes)

-- Send a frame containing the JPG image data.
-- This will be the first and final frame, and therefore this constitutes the entire message.
local finalFrame = true
success = ws:send_frame_bd(jpgData, finalFrame)
if not success then
    print(ws.last_error_text)
    return
end

-- Read the echoed binary frame(s).
-- (We sent the JPG file in a single frame, but we may receive the echo in multiple frames, but it will be one message.)
-- Read an incoming frames until we receive the final frame.
local receivedFinalFrame = false
while not receivedFinalFrame do
    -- The ws object is accumulating the received data internally.  Once we get the final frame, we'll get the
    -- accumulated data which should constitute the entire JPG.
    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

-- Get the accumulated received data.
local jpgReceivedData = chilkat.BinData.new()
ws:get_frame_data_bd(jpgReceivedData)
print("Received " .. jpgReceivedData.num_bytes .. " bytes")

-- Save the received JPG to a file so we can check it..
jpgReceivedData:write_file("qa_output/starfish_ws.jpg")

-- 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.")