How to receive UDP messages in Cordova application on mobile device?

Question

I have been programming for 2 months now and I want to make a mobile app, which will comunicate with a server on a PC in the same LAN. I am using NodeJS Dgram module and Socket.io. I am broadcasting messages on a server and I want to see those messages on my mobile device, so that when I start an app on a device, I will listen for messages and then make a socket connection to the address, where the message was sent from. I have seen a couple of examples/solutins on web, but I still do not understand and it just gets me more confused. Currently it works well because I broadcast from one PC and on another PC I run node client.js and then listen for those messages, but I would like to do the same, just on mobile device (Cordova platform).

The goal is that I will click a button and start listening for a broadcast messages if this is even possible.

Code for broadcasting - on the server:

const dgram = require('dgram');
            const broadcasts = this.getBroadcastAddresses();
            _broadcasting = setInterval(
                function (broadcasts, dgram, options) {
                    broadcasts.forEach(function (broadcast) {
                        const message = Buffer.from(options.data);
                        console.log(message);
                        const client = dgram.createSocket({ type: 'udp4', reuseAddr: true });
                        client.bind(8080, function () {
                            client.setBroadcast(true);
                            client.send(message, 0, message.length, 8080, broadcast, function (err, bytes) {
                                if (err) {
                                    console.error(err);
                                }
                                client.close();
                                if (options.hasOwnProperty('callback')) {
                                    options.callback(broadcast, err, bytes);
                                }
                                return;
                            });
                        });
                    });
                },
                options.timer * 1000,
                broadcasts,
                dgram,
                options
            );

Code for Client to listen for messages:

    if (util.platform === 'webkit') {
            var dgram = require('dgram');
            _socket = socket = dgram.createSocket({ type: 'udp4', reuseAddr: true });
            _socket.on('message', function (message, rinfo) {
                console.log('Message: ' + rinfo.address + ':' + rinfo.port + ' - ' + message);
            });
            _socket.on('listening', () => {
                options.bind_callback(socket.address());
            });

            _socket.bind(8080, '0.0.0.0');
        } else if (util.platform === 'cordova') {
            _socket = window.dgram.createSocket('udp4', 8080);
            _socket.on('message', (msg, remote) => {
                options.message_callback(msg.toString(), remote);
            });
            _socket.on('listening', () => {
                options.bind_callback(socket.address());
            });
            _socket.bind();
        }

score 0 · Answer 1 · answered Aug 07 '20 at 12:44

I solved it by installing Cordova plugin which can work with UDP protocol and it works like a charm.

The plugin is called cordova-plugin-datagram4 and it is version 1.0.2. You can find it on this link: https://www.npmjs.com/package/cordova-plugin-datagram4/v/1.0.2

Here is how I did it on the client-side:

getMaster: async () => {
            const datagram = cordova.require('cordova-plugin-datagram4.datagram');
            const _socket = datagram.createSocket('multicast-udp4');
            _socket.bind(port);
            _socket.on('listening', () => {
                let address = socket.address();
                console.log('UDP _socket listening on ' + address.address + ':' + address.port);
            });
            _socket.on('message', function (message, rinfo) {
                console.log('Message from: ' + rinfo.address + ':' + rinfo.port + ' - ' + message);
                document.getElementById('master-ip-field').value = rinfo.address;
                data.host = rinfo.address.trim();
                _socket.close();
                app.settings._makeConnection(rinfo.address);
            });
            return senderAddress;
        },

I call app.getMaster() to start listening to the UDP packets, sent from server-side(NodeJS server) in the same LAN.

How to receive UDP messages in Cordova application on mobile device?

1 Answers1