Star

Ever wanted to play a local game with a friend who is far away? Star makes local multiplayer games playable remotely!

Warning

This project is a work in progress.

How to Start

Deploy a Server

1. Build the server:

   make build registar

2. Copy the server binary to the target machine.

3. Run the server:

   sudo SECRET=my-secret CERT_DOMAINS=my-domain.com ./registar

   This will start a relay server named "registar", which listens on ports 80 and 443. See more about registar here.

Game Host

1. Host the game.
2. Run the client, click "Start a server" -> "Advanced settings."
3. Select the game port on which the game runs.
4. Enter the server's secret.
5. Enter the server's URL.
6. Click "Start".
7. Share the invite code with your friend.

Game Peer

1. Enter the invite code provided by the host.
2. Connect to the game.

Registar Server

The registar server is a relay server that relays UDP traffic over HTTP/3 using DATAGRAMs.

Features

• Automatic TLS certificate management with Let's Encrypt.
• Automatic redirects to HTTPS.
• HTTP/3 advertisement.

Configuration

The server can be configured using the following environment variables:

• SECRET - A secret to prevent unauthorized connections to the server (required).
• LISTEN_ADDRESS - The address to listen for HTTP traffic.
• LISTEN_TLS_ADDRESS - The address to listen for HTTPS and HTTP/3 traffic.
• LOG_LEVEL - The logging level (INFO, DEBUG).
• CERT_SELF_SIGNED - If set to true, enerates and uses a self-signed certificate instead of Let's Encrypt. Useful for testing.
• CERT_DIR - The path to the directory where certificates are stored.
• CERT_DOMAINS - A comma-separated list of domains for which to issue certificates (required).
• CERT_IP_ADDRESS - A comma-separated list of IP addresses for which to issue certificates.

Clients

Client is a simple WebView application that dynamically renders HTML pages using Go templates, served by a local HTTP server. See screenshots for a preview.

How It Works

In summary, it is a relay server with two types of clients: host and peer. The host and peer connect to each other via this relay server. It operates on top of HTTP/3 and relays UDP traffic using HTTP/3 DATAGRAMs.

Diagram

The mermaid diagram illustrates how the connection is established:

1. The Host Forwarder registers itself with the Server and issues a new invite key.
2. The Peer Forwarder waits for the Game Client to connect. On the first packet, it connects to the Server using the invite code.
3. The Server then asks the Host Forwarder to initiate a new connection to the Game Host.
4. The Host Forwarder and Peer Forwarder relay data between the Game Host and Game Client via the Server.

sequenceDiagram
  participant Game Host as Game Host
  participant Host Forwarder as Host Forwarder
  participant Server as Server
  participant Peer Forwarder as Peer Forwarder
  participant Game Client as Game Client

  Note left of Game Host: Game Host initiates connection
  Host Forwarder ->> Server: CONNECT Register Game
  Server ->>+ Host Forwarder: HTTP OK
  rect rgb(191, 223, 255, 0.3)
    Note right of Peer Forwarder: Game Client initiates connection
    Game Client ->> Peer Forwarder: Connect Game
    rect rgb(200, 150, 255, 0.3)
      Peer Forwarder ->>+ Server: CONNECT Connect Game
      
      Server ->> Host Forwarder: CONNECT

      Host Forwarder ->> Game Host: Dial
      Host Forwarder ->> Server: CONNECT
      Server ->> Host Forwarder: OK
      Server <<-->> Host Forwarder: DATAGRAM stream

      Server ->>- Peer Forwarder: HTTP OK
      Server <<-->> Peer Forwarder: DATAGRAM stream
    end

  end
  Note over Host Forwarder, Peer Forwarder: Server forwards data between two clients
  Peer Forwarder ->> Game Client: Forward
  Host Forwarder ->> Game Host: Forward

Loading

Development

Cross-Compilation for Windows:

To compile webview for Windows, mingw-w64 is required:

brew install mingw-w64

On Linux:

apt install binutils-mingw-w64 

Then build the app:

make build-webview-win

Testing HTTP API

Run the API:

SECRET=registar_secret LOG_LEVEL=DEBUG CERT_SELF_SIGNED=true go run ./cmd/registar/...

Here we tell our app to use a generated self-signed certificate: a certificate created by a self-signed Certificate Authority (CA).

During initialization, the app will also create a ca.crt file: a self-signed CA certificate. Use it to verify the server's certificate.

HTTP/1 or HTTP/2

Run in another terminal:

curl -Lv --cacert ca.crt http://localhost/-/health

HTTP/3

You can use a pre-built curl with HTTP/3 support from https://github.com/stunnel/static-curl.

Run in another terminal:

curl -Lv --cacert ca.crt --http3 http://localhost/-/health