React Native Post Request via Fetch throws Network Request Failed

Question

I´ve came across the following error. At the moment I developing an Android App with React Native therefore I´m planning to use fetch for doing a post request for me.

fetch("https://XXreachable-domainXX.de/api/test", {
            method: "post",

            body: JSON.stringify({
                param: 'param',
                param1: 'param',

            })
        }
    )
        .then((response) = > response.json()
    )
    .
    then((responseData) = > {
        ToastAndroid.show(
        "Response Body -> " + JSON.stringify(responseData.message), ToastAndroid.SHORT
    )
})
    .
    catch((error) = > {
        console.warn(error);
})
    ;

The app now throws an error:

TypeError: Network request failed

When I change the code to a GET-Request it´s working fine, in the browser with a window.alert() as a return it´s cool and also the chrome extension Postman returns data correctly.

Solution 1

This React Native's error is rather useless, so you need to get the actual underlying error first. The most straightforward way is to write a small native program that would just perform the same query using HttpsURLConnection.

For me the actual error was java.security.cert.CertPathValidatorException: Trust anchor for certification path not found. which has a well known solution: https://developer.android.com/training/articles/security-ssl.html#MissingCa

This is quite likely your case also, given that the browsers and Postman have no problem with the request. To check it run openssl s_client -connect XXreachable-domainXX.de:443 -showcerts. If there are certificate errors, fix them first, it could spare you time writing the native program.

Edit: actually the easiest way to see all underlying android errors for react native is simply running 'adb logcat' in terminal

Solution 2

Developing with Windows OS/PHP built-in server/react-native Android on device:

• check server local IP address (ipconfig), e.g. 172.16.0.10
• in react-native fetch use this URL and proper port (fetch('http://172.16.0.10:8000/api/foo))
• run PHP built-in server with this specific IP instead of the localhost: php -S 172.16.0.10:8000 ...
• turn off Windows firewall for the private networks

That fixed the connection problem between Android phone and the local server for me.

Solution 3

None of above answers were helped me. the problem was headers:

Old header:

fetch(API_HOST, {
                method: 'POST',
                headers: {
                    Accept: 'application/json'
                },
                body: JSON.stringify(data),

Updated header:

fetch(config.API_HOST, {
                method: 'POST',
                headers: {
                    Accept: 'application/json',
                    'Content-Type': 'application/json'  // I added this line
                },
                body: JSON.stringify(data),

Solution 4

If you have had this error and you are sure everything works well and you are running an emulator, simply close your emulator and fire it up again.

It should run now.

This usually happens after you have hibernated your system for a while

Solution 5

step1> add android:usesCleartextTraffic="true" line in AndroidManifest.xml like:

// add this line ... step2> Delete all debug folder from your android folder..

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