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Defold networking examples

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# DefNet
Defold Networking modules and examples, provided as a Defold library project.

## Preface
I often get questions about networking in Defold from our forum users. Sometimes it is as easy as "How do I make an HTTP call?" and I can point to the documentation for [http.request()](http://www.defold.com/ref/http/#http.request:url-method-callback--headers---post_data---options-) and everyone is happy. Other times the questions are more complex (often relating to socket connections) and in those cases the Defold documentation isn't enough.

Luckily for us Defold comes bundles with the excellent [LuaSocket](http://w3.impa.br/~diego/software/luasocket/home.html) library. With LuaSocket it is fairly trivial to create TCP and UDP sockets. Here's a bare-bones TCP socket example:

```
local client = socket.tcp()
client:connect(server_ip, server_port)
client:settimeout(0) -- non blocking socket
client:send(data) -- send data like this
local response = client:receive("*l") -- receive a "line" of data like this
```

The above snippet of code, some reading of the LuaSocket documentation and perhaps a couple of Google searches will get you quite far, but some concepts like peer to peer discovery is a bit trickier. The goal with this project is to collect some useful Lua networking modules that can be used either as-is or modified to suit your needs.

## Requirements

## Installation
You can use the modules from this project in your own project by adding this project as a [Defold library dependency](http://www.defold.com/manuals/libraries/). Open your game.project file and in the `dependencies` field under `project` add:

https://github.com/britzl/defnet/archive/master.zip

Or point to the ZIP file of a [specific release](https://github.com/britzl/defnet/releases).

## Peer to peer discovery
The `defnet/p2p_discovery` module can be used to perform peer to peer discovery using UDP sockets. The basic idea is that an app sets itself up as discoverable and starts sending a broadcast message on the network. Other clients can listen for broadcasted messages and get the IP of the app that wishes to be discovered. This is how an app can set itself up as discoverable:

```
local p2p_discovery = require "defnet.p2p_discovery"
local PORT = 50000

function init(self)
	self.p2p = p2p_discovery.create(PORT)
	self.p2p.broadcast("findme")
end

function update(self, dt)
	self.p2p.update()
end
```

And this is how another app would discover it:

```
local p2p_discovery = require "defnet.p2p_discovery"
local PORT = 50000

function init(self)
	self.p2p = p2p_discovery.create(PORT)
	self.p2p.listen("findme", function(ip, port, message)
		print("Found server", ip, port)
		print("Message", message)
		self.p2p.stop()
	end)
end

function update(self, dt)
	self.p2p.update()
end
```

Once discovery has been completed communication can take place over a socket of some kind.

NOTE: While it may be possible to test with two or more clients running on the same machine it is not always guaranteed to work. It is recommended to test P2P discovery on multiple machines for the most accurate results.

## TCP socket server
The `defnet/tcp_server` module can be used to create a TCP socket server that accepts incoming TCP client connections and can send and receive data. Example:

```
local function on_data(data, ip, port, client)
	print("Received", data, "from", ip)
	return "My response\n"
end

local function on_client_connected(ip, port, client)
	print("Client", ip, "connected")
end

local function on_client_disconnected(ip, port, client)
	print("Client", ip, "disconnected")
end

function init(self)
	self.server = tcp_server.create(8190, on_data, on_client_connected, on_client_disconnected)
	self.server.start()
end

function final(self)
	self.server.stop()
end

function update(self, dt)
	self.server.update()
end
```

## TCP socket client
The `defnet/tcp_client` module can be used to create a TCP socket client and connect it. Example:

```
local tcp_client = require "defnet.tcp_client"
local IP = "localhost" -- perhaps get IP from P2P discovery?
local PORT = 9189

function init(self)
	self.client = tcp_client.create(IP, PORT, function(data)
		print("TCP client received data " .. data)
	end,
	function()
		print("On disconnected")
		self.client = nil
	end)
end

function update(self, dt)
	if self.client then
		self.client.update()
	end
end

function on_input(self, action_id, action)
	-- on some condition do:
	self.client.send("Sending this to the server\n")
end
```

## UDP client
The `defnet/udp` module can be used to create an UDP connection. The connection can either be unconnected and send and receive data from any IP and port or connected and bound to a specific port and/or send only to a specific IP and port.

The module will simply forward any incoming data to a callback function. Example:

```
local udp = require "defnet.udp"

function init(self)
	self.udp_server = udp.create(function(data, ip, port)
		print("Received data", data, ip, port)
	end, 9999)

self.udp1 = udp.create(function(data, ip, port)
		print("Received data", data, ip, port)
	end, nil, "127.0.0.1", 9999)
	self.udp1.send("foobar to server")

self.udp2 = udp.create(function(data, ip, port)
		print("Received data", data, ip, port)
	end)
	self.udp2.send("foobar to server", "127.0.0.1", 9990)
end

function final(self)
	self.udp_server.destroy()
	self.udp1.destroy()
	self.udp2.destroy()
end

function update(self, dt)
	self.udp_server.update()
	self.udp1.update()
	self.udp2.update()
end
```

## HTTP server
Since it's possible to create a TCP socket it's also possible to build more advanced things such as HTTP servers. The `defnet/http_server` module can be used to create a simple HTTP server with basic page routing support. Example:

```
local http_sever = require "defnet.http_server"
local PORT = 9189

function init(self)
	self.hs = http_server.create(PORT)
	self.hs.router.get("/foo/(.*)$", function(matches)
		return self.http_server.html("boo" .. matches[1])
	end)
	self.hs.router.get("^/$", function()
		return self.http_server.html("Hello World")
	end)
	self.hs.router.get("^/stream$", function(matches, stream)
		return function()
			stream("some data")
		end
	end)
	self.hs.router.unhandled(function(method, uri)
		return self.http_server.html("Oops, couldn't find that one!", http_server.NOT_FOUND)
	end)
	self.hs.start()
end

function update(self, dt)
	self.hs.update()
end
```

## WebSockets
The WebSocket implementation for Defold has been [moved to a separate project](https://github.com/britzl/defold-websocket).

## Example
There's a few example projects in the examples folder.

## Found a bug? Made an improvement?
There are probably bugs. Please report them!

Did you improve some of the code? Please create a Pull Request!

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