React Native: Could not connect to development server

Question

I have a very simple React Native project that I am trying to get working. It is an iOS project that simply adds a RCTRootView to a UIViewController. When I run the app from Xcode I get a red screen with the error:

Could not connect to development server.

Ensure the following:
- Node server is running and available on the same network - run 'npm start' from react-native root
- Node server URL is correctly set in AppDelegate

AppDelegate.h

@property (strong, nonatomic) RCTRootView *rootView;

AppDelegate.m in application: didFinishLaunchingWithOptions:

NSURL *jsCodeLocation = [NSURL URLWithString:@"http://localhost:8081/index.ios.bundle?platform=ios"];
self.rootView = [[RCTRootView alloc] initWithBundleURL:jsCodeLocation moduleName:@"HelloReact" initialProperties:nil launchOptions:launchOptions];

ViewController.m in viewDidAppear:

AppDelegate *delegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
[self.view addSubview:delegate.rootView];

I am at a loss on how to resolve this. I have tried all of the following:

• npm start
• npm start --reset-cache
• Deleted node_modules directory and reinstalled
• Uninstalled and reinstalled node, watchman, react-native, and npm
• Tried on physical device and simulator

Does anyone see anything that is wrong in my code or know what the issue might be? I'd be willing to converse over email or phone to solve this. I am getting desperate.

I was having simultaneous issues. Here is the other question I asked which may contain some info: React Native: Unable to Resolve Module

Solution

Running a React Native app on an iOS device requires specifying the host machine's IP address instead of localhost:

jsCodeLocation = [NSURL URLWithString:@"http://DEV_SERVER_URI:8081/index.ios.bundle?platform=ios&dev=true"];

More specific instructions can be found in this answer.