handle network connection issues

Ought to close and reopen the `dgram` socket on network disconnect/reconnect.

Could be an optional feature:
```js
sACN.on('close', sACN.tryReopen);
```

Start by locating the `dgram` socket and the `sACN` close handling, including the proposed `sACN.tryReopen` entry point. Confirm the intended behavior for network disconnect and reconnect, then verify that the socket closes and reopens successfully without disrupting sACN operation.

Written by the indexing model from the issue text.