Handle EADDRINUSE event

```
events.js:71
          throw arguments[1]; // Unhandled 'error' event
                         ^
  Error: listen EADDRINUSE
      at errnoException (net.js:770:11)
      at Server._listen2 (net.js:910:14)
      at listen (net.js:932:10)
      at Server.listen (net.js:1006:9)
      at asyncCallback (dns.js:68:16)
      at Object.onanswer [as oncomplete] (dns.js:121:9)
```
