[ReactNative] Better error message for EADDRINUSE

packager/packager.js

@@ -23,6 +23,7 @@ if (!fs.existsSync(path.resolve(__dirname, '..', 'node_modules'))) {
   process.exit();
 }
 
+var chalk = require('chalk');
 var connect = require('connect');
 var ReactPackager = require('./react-packager');
 var blacklist = require('./blacklist.js');
@@ -88,13 +89,35 @@ console.log('\n' +
 ' ===============================================================\n'
 );
 
-console.log('Looking for JS files in\n  ', options.projectRoots.join('\n   '));
+console.log(
+  'Looking for JS files in\n  ',
+  chalk.dim(options.projectRoots.join('\n   ')),
+  '\n'
+);
 
 process.on('uncaughtException', function(e) {
-  console.error(e);
+  if (e.code === 'EADDRINUSE') {
-  console.error(e.stack);
+    console.log(
-  console.error('\n  >>> ERROR: could not create packager - please shut down ' +
+      chalk.bgRed.bold(' ERROR '),
-                'any existing instances that are already running.\n\n');
+      chalk.red('Packager can\'t listen on port', chalk.bold(options.port))
+    );
+    console.log('Most likely another process is already using this port');
+    console.log('Run the following command to find out which process:');
+    console.log('\n  ', chalk.bold('lsof -n -i4TCP:' + options.port), '\n');
+    console.log('You can either shut down the other process:');
+    console.log('\n  ', chalk.bold('kill -9 <PID>'), '\n');
+    console.log('or run packager on different port.');
+  } else {
+    console.log(chalk.bgRed.bold(' ERROR '), chalk.red(e.message));
+    var errorAttributes = JSON.stringify(e);
+    if (errorAttributes !== '{}') {
+      console.error(chalk.red(errorAttributes));
+    }
+    console.error(chalk.red(e.stack));
+  }
+  console.log('\nSee', chalk.underline('http://facebook.github.io/react-native/docs/troubleshooting.html'));
+  console.log('for common problems and solutions.');
+  process.exit(1);
 });
 
 var server = runServer(options, function() {
@@ -151,13 +174,13 @@ function getDevToolsLauncher(options) {
 }
 
 // A status page so the React/project.pbxproj build script
-// can verify that packager is running on 8081 and not 
+// can verify that packager is running on 8081 and not
 // another program / service.
 function statusPageMiddleware(req, res, next) {
   if (req.url === '/status') {
     res.end('packager-status:running');
   } else {
-    next();   
+    next();
   }
 }