React native staging environment setup... http://www.brysgo.com/development/tools/2015/07/26/react-native-on-heroku.html

AppDelegate.m

#import "AppDelegate.h"
#import "RCTRootView.h"

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    NSDictionary *env = [NSDictionary dictionaryWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"environment" ofType:@"plist"]];
    NSString *serverURLString = [NSString stringWithFormat:@"http://%@/index.ios.bundle", [env objectForKey:@"hostname"]];
    NSURL *codeURL = [NSURL URLWithString:serverURLString];
    RCTRootView *rootView = [[RCTRootView alloc] initWithBundleURL:codeURL
                                             moduleName:@"ChatApp"
                                          launchOptions:launchOptions];

  self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
  UIViewController *rootViewController = [[UIViewController alloc] init];
  rootViewController.view = rootView;
  self.window.rootViewController = rootViewController;
  [self.window makeKeyAndVisible];
  return YES;
}

@end

proxy.js

// server/proxy.js
var httpProxy = require('http-proxy');

var proxy = httpProxy.createProxyServer();

module.exports = function(http) {
  return http.createServer(function(req, res) {
    if (req.url.indexOf('index.ios') != -1) {
      proxy.web(req, res, { target: 'http://localhost:8081' });
    }
  });
}

server.js

// server/server.js
require('react-native/packager/packager.js');
var http = require('./proxy')(require('http'));
var io = require('socket.io')(http);
var port = process.env.PORT || 3000;

io.on('connection', function(socket){
  socket.on('chat message', function(msg){
    io.emit('chat message', msg);
  });
});

http.listen(port, function(){
  console.log('listening on *:' + port);
});

WebAPIUtils.js

// js/utils/WebAPIUtils.js
window.navigator.userAgent = "react-native";
var ServerActionCreators = require('../actions/ServerActionCreators');
var io = require('../../node_modules/socket.io/node_modules/socket.io-client/socket.io');
var React = require('react-native');
var EnvironmentManager = require('react-native-env');

var socket;
var serverUrl;

EnvironmentManager.get('hostname')
.then((val) => {
  serverUrl = 'http://' + val;

  socket = io(serverUrl, {jsonp: false});

  socket.on('connect', function(){
    socket.on('chat message', function(msg) {
      ServerActionCreators.receiveMessage(msg);
    });
  });
})

module.exports = {
  sendMessage: function(msg) {
    socket.emit('chat message', msg);
  }
};