Messaging with XMPP

Send and receive FCM messages directly between devices & your server with a XMPP server.

Introduction

This is a reference for using the Firebase Messaging service to send and receive messages directly between devices. Although methods (e.g. sendMessage()) are provided for sending and receiving message, additional configuration is needed to ensure a working solution for direct messaging from devices.

A custom solution is only required if plan to exchange messages directly between devices (including the message sender device) please ensure a solution from this article has been configured to successfully send and receive messages from a device.

The following describes how to set up a server to handle messages, including...

• A custom XMPP server with XCS for receiving messages.
• Firebase admin for sending messages.

So what are we going to do?

• Send a message from a client device.
• Intercept using a custom XMPP server.
• Push the message to Firebase using firebase-admin
• Receive the message and acknowledge on other connected devices.

Why can't I send and receive messages?

A common instance involves an implementation similar to the following.

firebase.messaging().onMessage(message => {
  console.log('Received a message');
});

firebase.messaging().onMessageSent(message => {
  console.log('Sent a message');
});

firebase.messaging().onSendError(message => {
  console.log('Received an Error');
});

firebase.messaging().sendMessage({
  data: {
    foo: 'bar',
  },
});

Although correct, none of the listeners will acknowledge a message or error.

Permissions are limited on the client meaning an additional solution is required to communicate between FCM and any connected devices.

How do I receive messages?

This is where you will need to deploy a custom server based, for example one based on Node XCS

Below is an example of how to configure a custom XMPP server using node-xcs.

const Sender = require('node-xcs').Sender;

async function operation() {
  return () => {
    console.log('Listening >>>');

    // Enter firebase credentials here. {SenderID, ServerKey}
    var xcs = new Sender('XXXXXXXX', 'XXXXXXXX');

    xcs.start();

    xcs.on('message', function (messageId, from, data, category) {
      console.log('received message', messageId, from, data, category);
    });

    xcs.on('receipt', function (messageId, from, data, category) {
      console.log('received receipt', arguments);
    });

    xcs.on('error', e => console.warn('XMPP error.', e));
  };
}

async function app() {
  await operation();
}

app();

How do I send messages?

For sending messages we can use the Firebase Admin SDK.

const admin = require('firebase-admin');
const serviceAccount = require('./service-account.json');

(async () => {
  admin.initializeApp({
    credential: admin.credential.cert(serviceAccount),
    databaseURL: 'XXXXXXXX',
  });

  await admin.messaging().send({
    token: 'XXXXXXX',
    data: {
      foo: 'bar',
    },
  });
})();