Run your own

The default demo.silt.run room is great for trying things out, but you can run the reference room server yourself. It’s a small pure relay written in Go: no game logic, no CRDT, no durable state — just membership, the join snapshot, and relaying the two lanes between peers.

This is the v0 reference server

The reference server runs a single warm room at /room/graveyard. The managed Silt platform — many rooms, scale-to-zero, wake-on-packet on Firecracker microVMs — is built on the same wire protocol. This page covers the local relay.

What it does

• Serves one WebTransport room at /room/graveyard.
• Relays presence datagrams and reliable events between peers (see the wire protocol).
• Tracks membership: sends each newcomer a snapshot, broadcasts join / leave, and distinguishes a clean bye ("left") from a dead session ("timeout").
• Generates a fresh ECDSA P-256 certificate at boot (validity ≤ 14 days, as required for serverCertificateHashes) and prints its SHA-256 hash.

Prerequisites

• Go (to build the server).
• A secure context for the browser: serve your page from https:// or http://127.0.0.1 / http://localhost. WebTransport refuses to connect from an insecure origin.

Build and run

1. Build the server

   cd room-server
   go build -o /tmp/silt-room-server .

2. Run it

   By default it binds 127.0.0.1:4433. Override with the WT_BIND env var.

   WT_BIND=127.0.0.1:4433 /tmp/silt-room-server

   On boot it prints the certificate hash and the listen address:

   CERT-SHA256-HEX: 9f86d081884c7d659a2feaa0c55ad015...
   silt room server listening on 127.0.0.1:4433  (room: /room/graveyard)

3. Connect with the cert hash

   Because the dev certificate is self-signed, pin it with the certHash option (the CERT-SHA256-HEX value the server printed). The room URL is your bind address plus the room path.

   import { joinRoom } from "@silt/client";
   
   const room = await joinRoom("https://127.0.0.1:4433/room/graveyard", {
     id: "alice",
     certHash: "9f86d081884c7d659a2feaa0c55ad015...", // CERT-SHA256-HEX from the log
   });

The cert hash changes on every boot

The server generates a new short-lived certificate each time it starts, so the certHash changes on every restart. For a real deployment behind a stable public hostname with a CA-issued cert, you connect by URL alone — no certHash needed.

The two-tab proof

The repo ships a local harness that builds the client and server, boots the server, scrapes the cert hash, and serves a demo page on a secure-context localhost port:

demo/run.sh
# then open in two browser tabs (set ?id=...):
#   http://127.0.0.1:8780/page.html?id=alice
#   http://127.0.0.1:8780/page.html?id=bob
demo/stop.sh

Move one peer and watch its presence sync to the other tab — two peers in one room, at zero box spend.

Next

• Wire protocol — exactly what the relay sends and receives.
• API reference — the certHash and other join options.