React Native Access mysql db using express - mysql

Question

I need to access my Data from my mysql Database using express, on my server the data is as a json, but when i try to access it i always get 'undefined' and my express server crash
the json i have on the server :
[{"idProjet":1,"nomProjet":"test","dateDebut":"2021-05-18T22:00:00.000Z","nomAuteur":"mathieu","prenomAuteur":"jean","organisme":"idmc"}]
fetching code :
let id = 'id :';
const [data, setData] = useState([]);
useEffect(() => {
fetch('http://localhost:3000/projets')
.then(response => {return response.json()})
.then((json => {console.log(json);setData(json);}))
.catch(error => console.error(error));
console.log(data);
}, []);
Route.js code :
const express = require('express');
const bodyParser = require('body-parser');
const mysql = require('mysql');
const connection = mysql.createPool({
host : 'localhost',
user : 'root',
password : '',
database : 'agora'
});
// Starting our app.
const app = express();
// Creating a GET route that returns data from the 'users' table.
app.get('/projets', function (req, res) {
// Connecting to the database.
connection.getConnection(function (err, connection) {
// Executing the MySQL query (select all data from the 'users' table).
connection.query('SELECT * FROM projet', function (error, results, fields) {
// If some error occurs, we throw an error.
if (error) throw error;
// Getting the 'response' from the database and sending it to our route. This is were the data is.
res.send(results)
});
});
});
// Starting our server.
app.listen(3000, () => {
console.log('Go to http://localhost:3000/projets so you can see the data.');
});

Answer 1

The most common problem for this type of behavior is that you are using react-native on an android emulator. Android Emulator is using an IP-address different from localhost on windows machine. For more information, check here the official documentation.
So you can forward your port on the same port used by the android emulator (10.0.2.2) or you can change the port to 80 so you won't have any problem
You can go check this answer here