[SOLVED] Node.js server on raspberry Pi 3B unreachable from React Native app after few succesful iterations

Issue

I'm currently working on a simple React Native which sends to a Node.js server hosted on a Raspberry Pi3B an order to switch on or off a led.

React Native code :

import React from 'react';
import {StyleSheet, Text, View, Button} from 'react-native';

export default class App extends React.Component {
  constructor(props){
        super(props);};

  led(couleur){
    fetch('http://XXX.XXX.XXX.XXX:XXX/switchOnOff', {
      method: 'POST',
      headers: {
      Accept: 'application/json',
      'Content-Type': 'application/json',
      },body: JSON.stringify({'couleur': couleur}),
      }).catch((error) => {
        console.error(error);
      });
  }
  render() {
    return (
      <View>

        <View style={styles.bleu}>
            <Button title="Bleu" color='blue' onPress={() => this.led('bleu')}/>
        </View>

      </View>
    );
  }

 }

On the Raspberry, I have the following for my Node.js server :

var express = require('express');
var fs = require("fs");
var bodyParser = require('body-parser'); 

var Gpio = require('onoff').Gpio,
led14 = new Gpio(14, 'out');     

var app = express();
app.use(bodyParser.json());

var allumer = false;

app.post('/switchOnOff', function (req, res) {
coul = req.body['couleur'];
console.log('working!');

var val = !allumer ? 1 : 0;

if (coul == 'bleu'){
led14.writeSync(val);}


led14.watch((err, mess) => {
    if (err){throw err }})
allumer = !allumer;
}
   });


var server = app.listen(8000, function () {
   var host = server.address().address
   var port = server.address().port
   console.log("Example app listening at http://%s:%s", host, port)
})

strangely, this is working 5 times in a row (I get in the server console "working!" printed five times, and the led is toggled on/off).

But then I get the following error :

From then, I'm not able to send data to the server using the React Native app...

Has anyone any idea ?

Thanks

Solution

Actually I got it :

the error was coming from the server side: I was missing one line of code res.end() which ends each request

Modified server side code :

app.post('/switchOnOff', function (req, res) {
   coul = req.body['couleur'];
   console.log('working!');

   var val = !allumer ? 1 : 0;

   if (coul == 'bleu'){
       led14.writeSync(val);}


   led14.watch((err, mess) => {
      if (err){throw err }})
   allumer = !allumer;
   }

  //#########solving line##########
  res.end
  });

Answered By - ere