HTTP server: WebSockets
An example of a HTTP server that handles websocket requests.
To start the server on the default port, call `Deno.serve` with the handler.
Deno.serve((req) => {First, we verify if the client is negotiating to upgrade to websockets. If not, we can give a status of 501 to specify we don't support plain http requests.
if (req.headers.get("upgrade") != "websocket") {
return new Response(null, { status: 501 });
}We can then upgrade the request to a websocket
const { socket, response } = Deno.upgradeWebSocket(req);We now have access to a standard websocket object. Let's handle the "open" event
socket.addEventListener("open", () => {
console.log("a client connected!");
});We can also handle messages in a similar way. Here we set up a simple ping / pong example.
socket.addEventListener("message", (event) => {
if (event.data === "ping") {
socket.send("pong");
}
});Lastly we return the response created from upgradeWebSocket.
return response;
});Run this example locally using the Deno CLI:
deno run --allow-net https://docs.deno.com/examples/scripts/http_server_websocket.ts