[iOS][Improvement] RCTWebSocketExecutor method could guess the devtools host via the ip.txt file

[yuriy-yarosh]

Is this a bug report?

Yes (Mostly)

Have you read the Contributing Guidelines?

Yes

Environment

1. react-native -v: 0.48.3
2. node -v: v8.4.0
3. npm -v: 5.3.0
4. yarn --version: 0.23.4

• Target Platform: iOS11

• Development Operating System: macOS 10.12.6 (16G29)

• Build tools: XCode 9 beta

Steps to Reproduce

1. Want to automate the RCTWebSocketExecutor react-devtools host detection.
2. sed -i '' it all the way... Anyways, I'm using ngrok, so, it's a bit bothersome.
3. Well, if RCTBundleURLProvider already has guessPackagerHost method which uses ip.txt file in the main bundle, we could use that to pass the hostname for the RCTWebSocketExecutor.

Expected Behavior

Less regex's and manual RCTWebSocketExecutor patching.

Actual Behavior

Official documentation states explicitly to patch the RCTWebSocketExecutor.m file which isn't a great way of handling such things.

[radko93]

@facebook-github-bot bugfix

[facebook-github-bot]

Hey @yuriy-yarosh, if you're sure this is a bug, can you send a pull request with a fix?

[yuriy-yarosh]

I've fixed it myself, will be making a PR today after looking into the Android counterpart.
Made some amends to docs.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Maybe the issue has been fixed in a recent release, or perhaps it is not affecting a lot of people. If you think this issue should definitely remain open, please let us know why. Thank you for your contributions.