nehal119 / go-udp-holepunch

UDP hole punch example in golang

UDP Hole Punching

This is a very simple repo to help demonstrate how UDP hole punching works in Go and Node. It includes the signal server and a client.

Using http rendezvous server

1. rendezvous server runs on http exposing /register route.
2. For http to work one has to send their public ip address and thier udp port in the /register route to work.
3. When two clients are connected, each get others udp ip address and port to start hole punching.

  node rendezvous/server.js # <- Signalling Server
  ./hp A # <-- client 1
  ./hp B # <-- client 2

• Note: For automatic IP and port detection, an HTTP signaling server cannot be used because it would identify the correct IP but the wrong port number. This is due to the UDP port on the client machine being different from the TCP port. To resolve this issue, the signaling server must be written exclusively for UDP. The functional signaling server code is available in server1.go for UDP and in rendezvous/publicserver.js for UDP combined with WebSocket.

Build

1. Build using golang 1.17

  go build -o hp .
  ./hp s  # <-- signaling server
  ./hp c1 # <-- client 1
  ./hp c2 # <-- client 2

Start background process

nohup ./hp s > output.txt 2>&1 < /dev/null & nohup node server.js > output.txt 2>&1 < /dev/null &

Usage

1. Set up signal server on a publicly accessible server.

./hp s :9595

2. Run client from a machine behind a firewall:

./hp c ip-address-of-signal:9595 :4545

3. Run client from a different machine behind a different firewall:

./hp c ip-address-of-signal:9595 :4545

After doing this the two machines behind firewalls should start sending Hello! back and forth to each other via UDP. You can shut off the signal server and they will still be able to communicate peer to peer.

API

For both the server and the client you can specify the local address and port. You may exclude the local address and specify just the port. This is what most use cases would do. Leaving this off entirely will use :9595 which is to say any local address on port :9595.

Server

./hp s [local-address:port]

Client

./hp c [signal-host:port] [local-address:port]

You may exclude the local address and specify just the port. This is what most use cases would do. Leaving this off entirely will use :9595

Notes

https://en.wikipedia.org/wiki/UDP_hole_punching

Peer-to-Peer Communication Across Network Address Translators