CODEWITHSUNDEEP
node.jsserver
MoeSattler
MoeSattler

Reputation: 6904

How can a server (node) let a client know that there are updates to fetch?

I am currently learning my way around a nodeJS server. I do client side rendering with ReactJS.

One thing I am wondering about is, when I have new data I need the client to fetch, how do I let the Client know? And what is the best way to do that?

For instance for some sort of chat or similar things.

Upvotes: 0

Views: 232

Answers (2)

Joey
Joey

Reputation: 203

Take a look at http://socket.io/

I can only offer an example.

server.js

io.sockets.on('connection', function(socket) {
  console.log(__dirname);
  // watching file
  fs.watchFile(__dirname + '/example.txt', function(curr, prev) {
    // on file change we can read the new file
    fs.readFile(__dirname + '/example.txt', function(err, data) {
      if (err) throw err;
      // parsing the new txt and make it json just my preference
      var json = parser.toJson(data);
      // send the new data to the client
      socket.volatile.emit('notification', json);
    });
  });

frontend.html 

<script src="socket.io/socket.io.js"></script>
    <script src="http://code.jquery.com/jquery-1.7.1.min.js"></script>
    <script>
    // creating a new websocket
    var socket = io.connect('http://localhost:8000');
    // on every message recived we print the new datas inside div
    socket.on('notification', function (data) {
        // json string into a valid javascript object
        var _data = JSON.parse(data);

        $('#container').html(_data.test.sample);
        $('time').html('Last Update:' + new Date());
    });
    </script>

So basically when my file of data was updated on the server, I used a websocket to keep a connection active between my server and client. It would update the clientside with new data from the file each time it was changed.

Upvotes: 1

ralh
ralh

Reputation: 2574

HTTP is a request - response protocol that can only be initiated client-side. So you need to look into workarounds like comet or long-polling, or into alternative technologies such as websockets, which allow two way communication in the browser.

http://www.pubnub.com/blog/http-long-polling/

http://socket.io/

Upvotes: 1

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