Cannot connect to Firebase Realtime Database (Node.js)

Question

My app cannot connect to Firebase Realtime Database. When I run the code below, the log 'not connected' is always printed. Moreover, the code ref.once('value', snapshot =>...) not return any result, nor error (hanging-up forever). Please tell me what is the problem with my code, and how to solve it. Thanks.

const firebase = require('firebase/app');
require('firebase/auth');
require('firebase/database');

const config = {
  apiKey: "...",
  authDomain: "...",
  databaseURL: "...",
  projectId: "...",
  storageBucket: "...",
  messagingSenderId: "...",
  appId: "..."
};
firebase.initializeApp(config);

function test() {
  //Test connnection (https://firebase.google.com/docs/database/web/offline-capabilities#section-connection-state)
  const connectedRef = firebase.database().ref('.info/connected');
  connectedRef.on('value', (snap) => {
    if (snap.val() === true) {
      console.log('connected');
    } else {
      console.error('not connected');
    }
  });

  //Test retrieve data.
  const ref = firebase.database().ref('/');
  ref.once('value', snapshot => {
    const data = snapshot.val();
    console.log(data);
  }).catch(error => {
    console.error(error);
  })
}
test();

PS: This is not duplicate of Cannot connect to Firebase Realtime Database

Answer 1

The issue maybe related to your Firewall settings, or Certification issue. For example, if your computer use an self-signed certificate, Node.js may throw an exception self signed certificate in certificate chain (and surprisingly Firebase client will silently ignore it without throwing up any exception, so try/catch won't work). You can check it by adding process.env["NODE_TLS_REJECT_UNAUTHORIZED"] = 0; to the very first code-line of your project (note that it's for testing only, since that code may cause security problem if used in production).