CODEWITHSUNDEEP
javascriptnode.jswebsocket
quartaela
quartaela

Reputation: 2757

websockets - get message from a websocket server and send it to client

I am trying to learn how websockets work. I am able to get trading data from a websocket server and print it on the console. However, I am trying to understand how I can pass that message into my websocket server so that I can send it to my websocket clients. Basically, I want to print each message on browser.

"use strict";

const WebSocket = require("ws");

const binanceWS = new WebSocket("wss://stream.binance.com:9443/ws/stratbtc@trade");

binanceWS.on("open", function open() {
    console.log("open action");
});

binanceWS.on("message", function incoming(data) {
    console.log(data);
});

Now this binanceWS will print data when it recieves one. The thing I am trying to do is how I can pass to the send eventlistener of my WebSocket.Server object. As you can see an example from https://github.com/websockets/ws wss itself takes a websocket object when there is a connection.

const wss = new WebSocket.Server({ port: 8080 });

wss.on('connection', function connection(ws) {
  ws.on('message', function incoming(message) {
    console.log('received: %s', message);
  });

  ws.send('something');
});

Thanks!

NOTE: The structure I am talking about is like this. Basically, I will have websocket consumers to get trade data. And within same host (localhost for now) there will be a websocket server. This websocket server will send data to each client websockets.

enter image description here

SUCCESS: Ok I made it by defining consumer websocket (binanceWS) message listener in websocket server connection. I am not sure if this is a good way though

"use strict";

const WebSocket = require("ws");

const binanceWS = new WebSocket("wss://stream.binance.com:9443/ws/stratbtc@trade");

binanceWS.on("open", function open() {
    console.log("open action");
});

const wss = new WebSocket.Server({ port: 8080 });

wss.on('connection', function connection(ws) {
  ws.on('message', function incoming(message) {
    console.log('received: %s', message);
  });

  binanceWS.on("message", function incoming(data) {
      ws.send(data);
  });
});

Upvotes: 4

Views: 35638

Answers (2)

quartaela
quartaela

Reputation: 2757

I achieved this my keeping a global list for websocket clients. And when consumer websocket message event is triggered, it sends every client by traversing list.

"use strict";

const WebSocket = require("ws");

const binanceWS = new WebSocket("wss://stream.binance.com:9443/ws/eosbtc@trade");

var websocketList = [];

binanceWS.on("open", function open() {
    console.log("open action");
});

binanceWS.on("message", function incoming(data) {
    console.log(data);

    // send data to every websocket client
    websocketList.forEach(ws => {
        ws.send(data);
    });
});

const wss = new WebSocket.Server({ port: 8080 });

wss.on("connection", function connection(ws) {

    // add ws handle to websocket list.
    websocketList.push(ws);

    ws.on("close", function close() {
        console.log("Disconnected");
    });
});

Upvotes: 3

edkeveked
edkeveked

Reputation: 18371

single websocket

//websocket connection event will return a socket you can later use
binanceWS.on("connection", function(socket) {
    socket.on("message", function incoming(data) {
    console.log(data);
    // if you want to send that message back to the client who sent it, 
    // you can use send method on the socket
     socket.send(data)
    });
});

Nesting websocket

//websocket connection event will return a socket you can later use
binanceWS.on("connection", function(socket) {
    // create another websocket here
    const wss = new WebSocket.Server({ port: 8080 });

    // connect the second websocket
     wss.on("connection", function(ws) {
      // start listening to first websocket incoming messages 
      // if second communication has successully been instantiated 
      socket.on("message", function incoming(data) {
      // send the data using the second websocket
      ws.send(data)
      })
    });
});

Then you need to have this minimum code in your client and you will see the interaction between the server and your client

client

const socket = new WebSocket('server_url'); // Connection opened 
socket.addEventListener('message', function (event) { socket.send('send message'); });

Note: Since you will use the incoming data of a websocket into another, it is best to open the second websocket only if the first one has successfully been opened

Upvotes: 1

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