TcpSocketServer

TcpSocketServer is different from the TcpSocket library because of the inbound/waiting nature of a TCP server. TcpSocket generally allows Q-SYS to establish outgoing TCP client sessions to remote TCP servers. The TcpSocketServer library enables a script to create a TCP "listener" on a specific TCP port. This listener isn't the individual TCP socket itself – it "emits" a unique TcpSocket instance whenever a remote TCP client connects to the listen port. Thus, the TcpSocketServer instance's EventHandler is where the specific incoming TCP socket connection is granted a unique socket instance (the argument of the TcpSocketServer's EventHandler function). The EventHandler target function for this new socket instance will be defined as an anonymous function or (more likely) as a reference to a separate socket event handling function.

Note: If multiple incoming socket connections are made, a separate socket instance (and EventHandler) are created by the Lua runtime engine for each connection and all socket transactions are handled by each socket connection's separate EventHandler instances (which are assigned only as necessary). The IP address of the connecting device will be available in each sock instance, see .PeerAddress for more information.

Note: The EventHandler arguments and function names in this example were chosen to assist in understanding what is happening when a TCP socket connection occurs. These names are not special and can be changed in your own scripts.

server = TcpSocketServer.New()

-- table to store connected client sockets
-- this is required so the sockets don't
-- get garbage collected since there aren't
-- any other references to them in the script
sockets = {}

function RemoveSocketFromTable(sock)
  for k,v in pairs(sockets) do
    if v == sock then 
      table.remove(sockets, k) 
      return
    end
  end
end
 

function SocketHandler(sock, event) -- the arguments for this EventHandler are documented in the EventHandler definition of TcpSocket Properties
  print( "TCP Socket Event: "..event )
  if event == TcpSocket.Events.Data then
    print( sock, sock:Read(sock.BufferLength) )
  elseif event == TcpSocket.Events.Closed or
         event == TcpSocket.Events.Error or
         event == TcpSocket.Events.Timeout then
    -- remove reference of socket from table so
    -- it's available for garbage collection
    RemoveSocketFromTable(sock)
  end
end
 
server.EventHandler = function(SocketInstance) -- the properties of this socket instance are those of the TcpSocket library
  SocketInstance.ReadTimeout = 10
  print( "Got connect", SocketInstance )
  table.insert(sockets, SocketInstance)
  SocketInstance.EventHandler = SocketHandler
end

server:Listen(1720) -- This listen port is opened on all network interfaces