JAVASCRIPT

socketio connect websockets

var ws = new WebSocket('ws://localhost/socket.io/?EIO=3&transport=websocket');
ws.send('42' + JSON.stringify(['hello', 'there']));
// ws.onmessage will get a MessageEvent object with the data property being encoded in the similar way.

socketio connect websockets

var socket = io('http://localhost');
socket.emit('hello', 'there');

socket io websocket connection

const socket = new WebSocket("ws://localhost:3000");

socket.addEventListener("open", () => {
  // send a message to the server
  socket.send(JSON.stringify({
    type: "hello from client",
    content: [ 3, "4" ]
  }));
});

// receive a message from the server
socket.addEventListener("message", ({ data }) => {
  const packet = JSON.parse(data);

  switch (packet.type) {
    case "hello from server":
      // ...
      break;
  }
});