A simple example using websockets that sends data and receives a response:

let url = "wss://echo.websocket.org"
let ws = new WebSocket(url);

ws.onmessage = function (event) {
    console.log("Received message:" + event.data);
}

ws.onopen = function (event) {
    console.log("Sent data over websocket");
    ws.send("Test");
}