demo · v143

Sub-protocol router

The use case ALPN was added for: one WebTransport endpoint, multiple application protocols (game state, chat, telemetry). Pick the client's offered list and the server's supported list; see which protocol gets negotiated and what the dispatched code does next.

1. client offers

2. server supports

handshake


      

      

        
after open: code that runs

        

      

    


    

  


  

    
the call


const wt = new WebTransport("https://game.example/connect", {
  protocols: ["game-v3", "game-v2", "chat-v1"],
});
await wt.ready;

switch (wt.protocol) {
  case "game-v3": runV3StateMachine(wt); break;
  case "game-v2": runV2StateMachine(wt); break;
  case "chat-v1": runChat(wt); break;
}

  


  

    
why this angle

    
The other concept tests the construction. This shows the router pattern the spec authors had in mind — one endpoint, many sub-protocols, branching on wt.protocol. It's the same pattern WebSocket sub-protocols established years ago.

  


  

    
see also