Bug Report: RNFS.downloadFile crashes with null pointer when server sends TCP RST (connection reset)

[Yakovyakov]

Bug Report: RNFS.downloadFile crashes with null pointer when server sends TCP RST (connection reset)

Problem Description

When RNFS.downloadFile() attempts to download from a server that sends a TCP RST (reset packet), the app crashes with a null pointer exception in native code instead of properly rejecting the promise with a network error.

Environment

• react-native-fs: 2.20.0
• React Native: 0.82.1

• Bug Report: RNFS.downloadFile crashes with null pointer when server sends TCP RST (connection reset)

Problem Description

When RNFS.downloadFile() attempts to download from a server that sends a TCP RST (reset packet), the app crashes with a null pointer exception in native code instead of properly rejecting the promise with a network error.

Environment

• react-native-fs: 2.20.0
• React Native: 0.72.0
• Platform: Android
• Device: Multiple Android devices

Steps to Reproduce

1. Set up a server that rejects connections with TCP RST (e.g., port closed, firewall blocking)
2. Attempt to download using RNFS.downloadFile()
3. Observe app crash instead of graceful error handling

Code to Reproduce

import RNFS from 'react-native-fs';

async function testDownload() {
  try {
    // Server that will send TCP RST (e.g., port 81 on a server that only has port 80 open)
    const result = await RNFS.downloadFile({
      fromUrl: 'https://example.com:81/nonexistent.apk',
      toFile: `${RNFS.DocumentDirectoryPath}/test.apk`,
      readTimeout: 30000,
      connectionTimeout: 30000,
    }).promise;
    
    console.log('Success:', result); // Never reached
  } catch (error) {
    console.log('Error caught:', error); // Never reached - app crashes
  }
}

### Steps to Reproduce
1. Set up a server that rejects connections with TCP RST (e.g., port closed, firewall blocking)
2. Attempt to download using `RNFS.downloadFile()`
3. Observe app crash instead of graceful error handling

### Code to Reproduce
```javascript
import RNFS from 'react-native-fs';

async function testDownload() {
  try {
    // Server that will send TCP RST (e.g., port 81 on a server that only has port 80 open)
    const result = await RNFS.downloadFile({
      fromUrl: 'https://example.com:81/nonexistent.apk',
      toFile: `${RNFS.DocumentDirectoryPath}/test.apk`,
      readTimeout: 30000,
      connectionTimeout: 30000,
    }).promise;
    
    console.log('Success:', result); // Never reached
  } catch (error) {
    console.log('Error caught:', error); // Never reached - app crashes
  }
}

[sahinboga]

./node_modules/react-native-fs/android/src/main/java/com/rnfs/RNFSManager.java

promise.reject(null, ex.getMessage()); => promise.reject("RNFS_GENERIC_ERROR", ex.getMessage());

This solved my problem

[marf]

Yes it need to changed in that way, can some mantainer release a new version?

[sahinboga]

@marf @dr.pogodin/react-native-fs Have you tried this package?

[marf]

@dr.pogodin/react-native-fs

Thank you for sharing, trying right now, seems it is fixed there!

[Yakovyakov]

Thank you both, @marf and @sahinboga. It's great to have a concrete solution and an alternative.

My plan is as follows:

1. Apply the fix you suggested (promise.reject("RNFS_GENERIC_ERROR", ...)) locally in my node_modules to verify that it resolves the NullPointerException when a RST is received.
2. Evaluate migrating to the @dr.pogodin/react-native-fs package as a long-term solution, as it seems more actively maintained.

I will share the outcome of both tests to contribute to the thread. I'll update this thread with my findings once I've completed the tests.

[Hemantkml]

react-native-fs+2.20.0.patch
Use this patch for

[chichilatte]

react-native-fs+2.20.0.patch Use this patch for

Thanks for the patch but it's gigantic (445KB) for a one-liner. Here's a small version...

diff --git a/node_modules/react-native-fs/android/src/main/java/com/rnfs/RNFSManager.java b/node_modules/react-native-fs/android/src/main/java/com/rnfs/RNFSManager.java
index 351ac06..fbfec13 100755
--- a/node_modules/react-native-fs/android/src/main/java/com/rnfs/RNFSManager.java
+++ b/node_modules/react-native-fs/android/src/main/java/com/rnfs/RNFSManager.java
@@ -975,7 +975,7 @@ public class RNFSManager extends ReactContextBaseJavaModule {
       return;
     }
 
-    promise.reject(null, ex.getMessage());
+    promise.reject("RNFS_GENERIC_ERROR", ex.getMessage());
   }
 
   private void rejectFileNotFound(Promise promise, String filepath) {

react-native-fs+2.20.0.patch

Note: I get this app crash happening when i call RNFS.downloadFile() with the device in airplane mode (RN 0.81, Android 16). So all in all a devastating bug!