clarifications

when the “second api” says it’s similar to the net interface, it means it’s a reliable stream, right? https://github.com/mafintosh/utp-native#socketonconnection-connection

this doesn’t mention how to do NAT hole punching, is there a module for that?

[mafintosh]

Yea! You’d basically only use a single utp instance in your entire app. Interesting idea about connecting to the known server using secret-handshake over utp as well. That would work great!

[mafintosh]

You need a central known server to distribute the external udp port of two peers to the corresponding peers. Here a quick gist of what this could look like.

// server.js
var dgram = require('dgram')
var server = dgram.createSocket('udp4')
var otherRinfo = null

server.on('message', function (message, rinfo) {
  if (otherRinfo) {
    send(otherRinfo, rinfo)
    send(rinfo, otherRinfo)
  }
  otherRinfo = rinfo
})

server.bind(10000)

function send (rinfo, to) {
  var buf = Buffer(JSON.stringify({host: rinfo.address, port: rinfo.port}))
  server.send(buf, 0, buf.length, to.port, to.address)
}

The clients

var utp = require('utp-native')

var socket = utp()

socket.on('message', function (message) {
  // server send us a peer, try and connect
  var otherPeer = JSON.parse(message)
  var connection = socket.connect(otherPeer.port, otherPeer.host)

  connection.write('hello world')
})

// emitted when a new utp connection is established
socket.on('connection', function (connection) {
  console.log('new peer')
  connection.pipe(process.stdout)
})

// send udp message to known-server.com
socket.bind(0, function () {
  socket.send(Buffer('hello'), 0, 5, 10000, 'known-server.com')
})

This is probably the minimum needed for hole punching