ESP8266 Community Forum

Posted: **Thu Sep 12, 2019 5:29 pm**

I want to use NodeMCU to act as a websocket server to 1 or more browser clients.

Luckily, there is code to do this here:
https://github.com/moononournation/nodemcu-webide/blob/master/bin/httpserver-websocket.lua
(courtesy of @creationix and/or @moononournation)

This works as described and I am able to send a message from the client to the NodeMCU server, which then responds based on the received message. Great.

My questions are:

1: How can I send messages to the client without it having to be sent as a response to a client request (standalone sending of data)? When I try to call socket.send() socket is not found as a variable, which I understand, but cannot work out how to do it!

Maybe it's because socket = {} is declared locally?

2: Why does the decode() function output the extra variable? What is this for? I'm assuming it will be for packet overflow, but I can never seem to make it return anything, regardless of my message length.

3: In the listen method, why has the author added a queuing system? is this essential or for applications that perhaps may receive multiple simultaneous messages? Ideally, I'd like to remove it.

I have simplified the code as below:

(excluding the decode() and encode() functions - please see the link above for the full script)

Code: Select all

net.createServer(net.TCP):listen(80, function(conn)

  local buffer = false
  local socket = {}
  local queue = {}
  local waiting = false

  local function onSend()
    if queue[1] then
      local data = table.remove(queue, 1)
      return conn:send(data, onSend)
    end
    waiting = false
  end

  function socket.send(...)
    local data = encode(...)
    if not waiting then
      waiting = true
      conn:send(data, onSend)
    else
      queue[#queue + 1] = data
    end
  end

  conn:on("receive", function(_, chunk)

    if buffer then
      buffer = buffer .. chunk
      while true do
        local extra, payload, opcode = decode(buffer)

        if opcode==8 then
          print("Websocket client disconnected")
        end

        --print(type(extra), payload, opcode)
        if not extra then return end
        buffer = extra
        socket.onmessage(payload, opcode)
      end
    end

    local _, e, method = string.find(chunk, "([A-Z]+) /[^\r]* HTTP/%d%.%d\r\n")
    local key, name, value

    for name, value in string.gmatch(chunk, "([^ ]+): *([^\r]+)\r\n") do
      if string.lower(name) == "sec-websocket-key" then
        key = value
        break
      end
    end

    if method == "GET" and key then

      acceptkey=crypto.toBase64(crypto.hash("sha1", key.."258EAFA5-E914-47DA-95CA-C5AB0DC85B11"))

      conn:send(
        "HTTP/1.1 101 Switching Protocols\r\n"..
        "Upgrade: websocket\r\nConnection: Upgrade\r\n"..
        "Sec-WebSocket-Accept: "..acceptkey.."\r\n\r\n",
        function () 

          print("New websocket client connected")

          function socket.onmessage(payload,opcode)
            socket.send("GOT YOUR DATA", 1)
            print("PAYLOAD = "..payload)
            --print("OPCODE = "..opcode)
          end

        end)
      buffer = ""
    else
      conn:send(
        "HTTP/1.1 200 OK\r\nContent-Type: text/plain\r\nContent-Length: 12\r\n\r\nHello World!",
        conn.close)
    end

  end)
end)

Any help would be much appreciated! Thanks

ESP8266 Community Forum

Pushing data to websocket browser client in Lua

Pushing data to websocket browser client in Lua