cb firing multiple times

Near line 178, this code doesn't set cbFired to true:

``` javascript
onError = function(reason) {
        if (!cbFired && typeof cb === 'function') {
          cb(new Error(reason));
        }
      },
      onClose = function() {
        if (!cbFired && typeof cb === 'function') {
          cb();
        }
      },
```

If a TCP error occurs, the callback is called twice.
