With React-Native, SSE aka EventSource does not receive Events on Android

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Description

I am trying to use rn-eventsource and react-native-event-source and they always get 200 status when sending a request to the server. However! I am able to receive Events on:

• iOS emulator
• my iOS device

but not from:

• Android emulator
• my Android device

I can get webpages with the browser provided EventSource to work on Chrome on ios and on Android.

It seems like this is an issue with React-Native on Android.

React Native version:

react-native info
info Fetching system and libraries information...
System:
    OS: macOS 10.15.4
    CPU: (8) x64 Intel(R) Core(TM) i7-4870HQ CPU @ 2.50GHz
    Memory: 62.51 MB / 16.00 GB
    Shell: 3.2.57 - /bin/bash
  Binaries:
    Node: 13.3.0 - ~/.nvm/versions/node/v13.3.0/bin/node
    Yarn: 1.22.4 - /usr/local/bin/yarn
    npm: 6.13.1 - ~/.nvm/versions/node/v13.3.0/bin/npm
    Watchman: 4.9.0 - /usr/local/bin/watchman
  Managers:
    CocoaPods: 1.9.1 - /usr/local/bin/pod
  SDKs:
    iOS SDK:
      Platforms: iOS 13.4, DriverKit 19.0, macOS 10.15, tvOS 13.4, watchOS 6.2
    Android SDK: Not Found
  IDEs:
    Android Studio: 3.6 AI-192.7142.36.36.6241897
    Xcode: 11.4.1/11E503a - /usr/bin/xcodebuild
  Languages:
    Java: 11.0.2 - /usr/bin/javac
    Python: 2.7.16 - /usr/bin/python
  npmPackages:
    @react-native-community/cli: Not Found
    react: 16.11.0 => 16.11.0
    react-native: ^0.62.2 => 0.62.2
  npmGlobalPackages:
    *react-native*: Not Found

Steps To Reproduce

Provide a detailed list of steps that reproduce the issue.

1. Install rn-eventsource or react-native-event-source
2. Setup a simple EventSource("https://..../sse_listen")
3. setup .onmessage, .onopen and .onerror which do console.log
4. Look at the logs emitted by .onmessage .onopen and .onerror
5. Notice that logs appear for iOS but not for Android

Expected Results

Events appear on Android

More details: I’m pasting the comments I added to this thread : https://github.com/react-native-community/discussions-and-proposals/issues/99 ::

I'm having trouble getting this to work at all on my Android device and on my Android emulator. The server does receive the GET request, but the client never receives any messages. I'm not sure how to troubleshoot or debug this at all.

It works on ios and ios emulator, it works in Chrome App on ios and Android. I tried using mitmweb but that didn't show the returned Events.

In the Android Studio Network Traffic Monitoring tool, the returned events do not show up.

tail -f /var/log/nginx/error.log doesn't seem to show any issues.

Here are the differences in the headers sent in the request:

Android
{
"x-forwarded-for":"ip",
"host":"mysite.com",
"connection":"close",
"cache-control":"no-store",
"accept":"text/event-stream",
"user-agent":"okhttp/3.14.1"
"accept-encoding":"gzip",
}

iphone:
{
"x-forwarded-for":"ip",
"host":"mysite.com",
"connection":"close",
"cache-control":"no-store"
"accept":"text/event-stream",
"user-agent":"AppName/1 CFNetwork/1121.2.2 Darwin/19.3.0",
"accept-encoding":"gzip, deflate, br",
"accept-language":"en-us",

}

I'm not sure if the issue is with RCTNetworking or with rn-eventsource. My guess is that since this is failing with both rn-eventsource and with simple xhr, that the issue is in RCTNetworking?