Receive and send data over TCP communication with LM

Example: Receive and send data over TCP communication with LM

One of possibilities how to exchange the data with external servers is by using TCP requests.

Logic Machine as a client

Source code     
  1. -- init socket
  2. if not sock then
  3.   require('socket')
  4.  
  5.   sock, err = socket.connect('192.168.1.1', 12345)
  6.  
  7.   -- set timeout to 1 second
  8.   if sock then
  9.     sock:settimeout(1)
  10.   -- error opening connection, log error and wait before reconnecting  
  11.   else
  12.     error(err)
  13.     sleep(5)
  14.   end
  15. end
  16.  
  17. -- socket handler
  18. if sock then
  19.   -- send data to socket
  20.   sock:send('1234567890')
  21.  
  22.   -- get 10 bytes of data from socket or wait for timeout
  23.   data = sock:receive(10)
  24.   -- got data, log it
  25.   if data then
  26.     log(data)
  27.   end
  28. end

Logic Machine as a server

  • LM can handle multiple TCP connections on the same port. A handler function should be defined which will be called for each connection established.
  • Broken connections can be traced using keep-alive packets (enabled using single function call). If connection is broken then usually you just have to close the connection and exit the handler functions.
  • Handler example:
Source code     
  1. -- server init
  2. if no server then
  3.   -- handler function
  4.   function handler(sock)
  5.     -- enable keep-alive check
  6.     sock:setoption('keepalive', true)
  7.  
  8.     local ip, port = sock:getpeername()
  9.     alert('connection from ' .. ip .. ':' .. port)
  10.  
  11.     -- main reader loop
  12.     while true do
  13.       -- wait for 10 bytes of data
  14.       local data, err = copas.receive(sock, 10)
  15.  
  16.       -- error, stop handler for this connection
  17.       if err then
  18.         list[ meta.id ] = nil
  19.         return
  20.       end
  21.  
  22.       -- do something with data and send reply to socket
  23.       result = dosomething(data)
  24.       copas.send(sock, result)
  25.     end
  26.   end
  27.  
  28.   require('copas')
  29.   -- bind on port 12345
  30.   server, err = socket.bind('*', 12345)
  31.  
  32.   -- cannot bind to port, wait and return error
  33.   if not server then
  34.     sleep(5)
  35.     error(err)
  36.   end
  37.  
  38.   copas.addserver(server, handler)
  39. end
  40.  
  41. -- handle communication for 1 second
  42. copas.step(1)