How to Connect to localhost with React Native

Описание: Struggling to connect your React Native app to a locally hosted API? This comprehensive guide shows you how to effectively connect to `localhost` using Android emulators and provides simple solutions for common issues.
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This video is based on the question https://stackoverflow.com/q/67083014/ asked by the user 'Avinash Sivaraman' ( https://stackoverflow.com/u/15627224/ ) and on the answer https://stackoverflow.com/a/67083262/ provided by the user 'Vinicius Petrachin' ( https://stackoverflow.com/u/6791214/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Connecting to localhost with React Native

If you are working with React Native and trying to connect to a locally hosted Express API, you might encounter some perplexing issues related to network requests. One such common problem is when your app fails to fetch data from localhost, resulting in a frustrating "Network request failed" error. Don’t worry; this guide will break down how to successfully connect your React Native application to your local development server.

Understanding the Problem

When you attempt to fetch data from your Express API using the following piece of React Native code:

[[See Video to Reveal this Text or Code Snippet]]

You may see errors similar to this:

[[See Video to Reveal this Text or Code Snippet]]

This occurs because Android emulators do not recognize localhost as your machine's local server. Instead, they treat localhost as the emulator’s own internal server.

Solutions to Connect to Localhost

To solve this problem effectively, follow the two provided solutions:

Solution 1: Use adb reverse

To redirect the network traffic from the emulator to your local server, you can use the command-line tool adb. Open your terminal or command prompt and run the following command while your emulator is running:

[[See Video to Reveal this Text or Code Snippet]]

This command tells the Android emulator to send requests made to localhost:5000 to your computer's localhost:5000. Now, you should be able to access your API using the original request:

[[See Video to Reveal this Text or Code Snippet]]

Solution 2: Use the IP Address 10.0.2.2

If for some reason the first solution did not work for you, you can bypass the issue by using a special IP address that Android emulators recognize. Instead of using localhost, replace it in your code with:

[[See Video to Reveal this Text or Code Snippet]]

This IP address (10.0.2.2) maps to localhost on your development machine when using an Android emulator.

Why These Solutions Work

adb reverse: This command effectively redirects your requests from the emulator port to your local machine’s port, allowing seamless communication between the two.

Using 10.0.2.2: This IP is a built-in loopback address for Android emulators, directing calls made using it to your local machine's server, bypassing the need for the adb reverse command.

Additional Notes

If you are developing on a Mac, you might not encounter this issue, as macOS recognizes localhost without any troubles, unlike Android emulators.

Ensure your local server is running and accessible, as connectivity issues unrelated to code might occur.

Conclusion

Connecting your React Native app to a locally hosted Express API can initially seem complicated due to issues like the one discussed. However, utilizing the right commands and IP addresses can effectively resolve these problems. With these solutions, you can retrieve your data seamlessly and move forward with your development process.

If you encounter any further issues or have questions regarding this topic, feel free to ask!