NPLTCPServer

NPL TCP Server

One can send or receive any custom messages on a NPL TCP connection. This is usually when the NPL client needs to communicate with a server with custom TCP protocol like google protocol buffer. Or one wants to write a server that is able to handle requests in custom TCP protocol rather than the default NPL protocol. Please note, the default NPL protocol is always recommended when communicating between two NPL nodes. We can dynamically switch between three protocols on the same TCP connections, namely NPL, WebSocket and custom TCP. This section is mainly about writing custom TCP client/server applications.

Writing Custom TCP server

• Registering a npl file to receive custom TCP message

-- -30 is a predefined file id for web socket. this is need on both client and server
NPL.AddPublicFile("script/test/network/tcp_server.lua", -30);
-- a server that listen on 8099 for all IP addresses
NPL.StartNetServer("0.0.0.0", "8099");

• Receiving message

--script/test/network/tcp_server.lua
local function activate()
	local user_id = msg.tid or msg.nid;
    local binary_data = msg[1];
    echo("partial data received:"..binary_data);
	if(math.random() < 0.5) then
		-- this is how server can send a message back to client
		NPL.activate(format("%s:tcp", user_id), "replied"..binary_data);
	end
end
NPL.this(activate)

Writing Custom TCP Client

	-- this only needs to called once to name a remote TCP server
	-- -30 is a predefined file id for web socket. this is need on both client and server
	NPL.AddPublicFile("script/test/network/tcp_server.lua", -30);
	NPL.StartNetServer("0.0.0.0", "0");
	local server_nid = "myserver01";
	NPL.AddNPLRuntimeAddress({host="127.0.0.1", port="8099", nid=server_nid})
	

	local server_addr = string.format("%s:tcp",server_nid);

	-- connect with 2 seconds timeout
	-- if the first message begins with \0 or non-char character, we will automatically use a custom TCP connection
	if(NPL.activate_with_timeout(2, server_addr, "\0first_binary_message") == 0) then
		-- now let us send some arbitrary binary message
		for i=1,10 do
			NPL.activate(server_addr, "i=\0"..i);
		end
	end