Network request failed (device and emulator)

Hello,

I am getting the error “Network request failed” (device and emulator) while accessing the URL https://reqweb.cast.com.br:5443/RequerimentoRest/req/login via fetch (). I can access this link via Postman or browser normally.

I wonder if there is a solution for this.

My code is:

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

export default class App extends React.Component {
    componentDidMount(){
        return fetch('https://reqweb.cast.com.br:5443/RequerimentoRest/req/login')
            .then((response) => response.json())
            .then((responseJson) => {
                console.log(responseJson);
            }).catch((error) =>{
                console.error(error);
                alert(error);
            });
    }

    render() {
        return (
            <View style={{flex: 1, paddingTop:20}}>
                <Text>Test Rest</Text>
            </View>
        );
    }
}

Thank you very much in advance.

[aprilmintacpineda]

@viniciuscastelano @ljtijhuis @ide

After going to sleep and upon waking up, I figured out what the answer was. I seem to have forgotten networking fundamentals.

What’s going on here?

I’m pretty new to expo and how it managed to push my app on my phone with wireless connection was a magic at first until I remembered networking. Basically expo pushes the app using the “lan” connection (in my case), your PC and the mobile you are using must be connected to the same network for this to work. Don’t get me wrong I don’t fully understand how expo works on the foundation level though I’d love to know the secret spell for its magic. (LOLS).

My computer is running the localhost server (nodejs) on localhost port 3000 (localhost:3000), so I need to make a request to the computer’s port 3000 in order for this to work, unfortunately for me, I was getting my IP thru https://duckduckgo.com/?q=what’s+my+ip%3F&atb=v113-7_y which didn’t work because I’m running on LAN so it needs to be the IP on the LAN network. So what you need is LANIP:3000/path/to/request for this network request to work.

Find out what your IP is: https://www.wikihow.com/Check-the-IP-Address-in-Linux

Now that you know your IP address, instead of doing http://localhost:3000/a-request do http://TheIpGoesHere:3000/a-request, in this case, your phone will make a request to your PC’s port 3000 where the localhost is running. Example: http://192.168.1.2:3000/login.

If someone can explain this better or can add more information as to why the other works and why the other ones don’t, please mention me.

BTW, I’m using the terminal so to run expo in LAN mode you should do: exp start --lan add a -c to clear the cache. More info at https://docs.expo.io/versions/v27.0.0/workflow/exp-cli. After running in LAN mode you should a url that’s something like this: 11:46:00 [exp] Your URL is: exp://192.168.1.2:19000

I hope this helps.

[aprilmintacpineda]

I think it would be good to add these kind of info to the docs. “Making network requests to your localhost”. Then add “Using an emulator.” and “Using your phone.”.