title: NodeMCU lua function "conn"
body: <p>I have maybe a weird question but I need to know this. Im creating a lua script to connect esp8266 and my mqtt broker. The example script is very straight forward.</p>
  
  <pre><code>m = mqtt.Client("clientid", 120, "user", "password")
  
  m:lwt("/lwt", "offline", 0, 0)
  
  m:on("connect", function(con) print ("connected") end)
  m:on("offline", function(con) print ("offline") end)
  
  m:on("message", function(conn, topic, data) 
    print(topic .. ":" ) 
    if data ~= nil then
      print(data)
    end
  end)
  
  m:connect("192.168.11.118", 1880, 0, function(conn) 
      print("connected") 
  end)
  
  m:subscribe("/topic",0, function(conn) 
      print("subscribe success") 
  end)
  
  m:publish("/topic","hello",0,0, function(conn) 
      print("sent") 
  end)
  
  m:close();
  </code></pre>
  
  <p>But... there is one thing I can't get over. That is the "con" and "conn" parameter? It looks like an instance or something, but there is no such a thing defined. Can somebody explain this to me?</p>