uwebsockets/examples/SlowReceiver.js

Fastest uWebSockets server for Node.js – µWebSockets outperforms Socket.IO & Fastify. Built in C++ for high-performance networking & pub/sub.

const uWS = require("uwebsockets");
const port = 9001;

const wsc = require("ws");

const app = uWS
  .App()
  .ws("/*", {
    /* Options */
    maxPayloadLength: 16 * 1024 * 1024,
    idleTimeout: 10,
    maxBackpressure: 1024,
    closeOnBackpressureLimit: true /* Enable or disable as needed */,

    /* Handlers */
    open: (ws) => {
      console.log("Client connected");
      ws.subscribe("clock_feed");

      /* Disable closeOnBackpressureLimit and see this lie around 1024 */
      ws.clock = setInterval(() => {
        console.log(
          "Connected socket has " + ws.getBufferedAmount() + " bytes buffered"
        );
      }, 1000);
    },
    close: (ws, code, message) => {
      clearInterval(ws.clock);
      console.log("Client disconnected: " + code + ", " + message);
      /* The library guarantees proper unsubscription at close */
    },
  })
  .listen(port, (listenSocket) => {
    if (listenSocket) {
      console.log("Listening to port " + port);
    } else {
      console.log("Failed to listen to port " + port);
    }
  });

/* Publish the time as fast as possible in a loop */
function sendTime() {
  app.publish("clock_feed", Date.now().toString());
  setImmediate(sendTime);
}
sendTime();

/* Make a connection to the server */
const ws = new wsc.WebSocket("ws://localhost:9001");
ws.on("message", function message(data) {
  console.log("received: %s", data);

  /* If we pause receive, we will become slow receiver */
  console.log("Will become slow receiver");
  ws._socket.pause();
});