Add troubleshooting section

README.md

@@ -13,6 +13,20 @@ Pre-built files can be found in either [roslib.js](build/roslib.js) or [roslib.m
 
 Alternatively, you can use the current release via the Robot Web Tools CDN: ([full](http://cdn.robotwebtools.org/roslibjs/current/roslib.js)) | ([min](http://cdn.robotwebtools.org/roslibjs/current/roslib.min.js))
 
+### Troubleshooting
+
+1. Check that connection is established. You can listen to error and
+   connection events to report them to console. See
+   examples/simple.html for a complete example:
+
+    ros.on('error', function(error) { console.log( error ); });
+    ros.on('connection', function() { console.log('Connection made!'); });
+
+1. Check that you have the websocket server is running on
+   port 9090. Something like this should do:
+
+    netstat -a | grep 9090
+
 ### Dependencies
 roslibjs depends on: