Golang WebRTC Signaling Server

WebRTC signal server with SSL support written in Go. Supports hosting and joining lobbies. Includes Godot client. I built this to allow WebRTC connections from web builds in Godot which requires SSL. It also works with other build types.

Note: Non-web builds require installing additional WebRTC libraries. See webrtc.html#using-webrtc-in-godot

Note: Currently, it is assumed this will be run somewhere on your LAN and that IPs can be resolved locally. I may extend this in the future for WAN usage.

Project Architecture

• /client (SignalWsClient class) - Godot client code. Provides a SignalLobby node via a Godot plugin.
  • SignalLobby node (signal_lobby_node.gd and signal_lobby_node.tscn) - Handles signals from SignalWsClient class and creates a WebRTC mesh using Godot's multiplayer apis
  • SignalWsClient class (scripts/client.gd) - manages the client websocket connection and a SignalWsPeer instance
  • SignalWsMsg class (scripts/msg.gd) - defines message types and handles serialization / deserialization of messages.
  • SignalWsPeer class (scripts/peer.gd) -
• /server - Golang signaling server

Messages

The server and client communicate over a websocket connection to establish a peer to peer WebRTC connection. Messages are identified by a numeric enum type:

enum Type {
	INVALID = 0,
	CONNECTED,
	HOST,
	JOIN,
	PEER_CONNECT,
	PEER_DISCONNECT,
	OFFER,
	ANSWER,
	CANDIDATE,
	SEAL
}

Messages are passing in a simple serialized format in the form of type|pid|data:

• type - numeric string for the msg type
• pid - peer id identifiying a peer in the WebRTC mesh
• data - optional data used by some message type

Client

The client code can be installed as a Godot plugin

1. Copy the /client folder to the /addons folder in a Godot project

2. Enable the Godot Golang WebRTC Signal plugin in the Plugins tab of Project settings

   

3. The plugin provides a SignalLobby node that can be added to a scene

   

4. After adding the node to a scene, you can right-click on the node and select % Access as Unique Name. The node should now show a % character.

   

5. You can now connect to the player_added and lobby_sealed signals:

   @onready var signal_lobby = %SignalLobby # SignalLobby node set to "% Access as Unique Name"
   
   func _ready() -> void:
      signal_lobby.player_added.connect(_on_player_added)
      signal_lobby.lobby_sealed.connect(_on_lobby_sealed)

Server

Running Locally

In the /server directory, you can start the server by running:

go run cmd/main.go

To use an SSL cert, you'll need to place a .crt and .key file in the /server directory with the same base name. e.g. ssl.crt and ssl.key

Then use the -cert flag to provide the cert base name.

go run cmd/main.go -cert ssl

Deployment

1. To build the server run:

scripts/build.sh

1. This will build an executable build/signalserver
2. Copy the executable to wherever you want to run it

To use an SSL cert, you'll need to place a .crt and .key file in the same directory as the executable with the same base name. e.g. ssl.crt and ssl.key

Then use the -cert flag to provide the cert base name.

./signalserver -cert ssl

Systemd Config

The server can be configured via systemd on a linux server such as a Raspberry Pi.

1. Open a new config file for the service:

   sudo nano /etc/systemd/system/gowebrtcsignal.service

2. Copy / paste the following template filling in and placeholders

   [Unit]
   Description = Go WebRTC Signaling Server
   
   [Service]
   Type             = simple
   Restart          = always
   RestartSec       = 5s
   StandardOutput   = append:<APPDIR>/stdout.log
   StandardError    = append:<APPDIR>/stderr.log
   ExecStart        = <APPDIR>/signalserver
   WorkingDirectory = <APPDIR>
   User             = <USER>
   
   [Install]
   WantedBy = multi-user.target

3. Enable and start the service

sudo systemctl enable gowebrtcsignal.service
sudo systemctl start gowebrtcsignal.service
sudo systemctl status gowebrtcsignal.service