It only sleeps if the connection is not active and the writing and transmission across the wire fails (which would only be possible in a non-blocking mode but it should be a blocking action).

Also, an until block will not execute the blocks contents if the condition returns true on the first call. You can test this like so:

```ruby
> def test
>   until true
>     puts 'hi'
>   end
> end
> test
```

If the block executes, hi will be printed, otherwise nothing (I had to confirm this for myself to make sure I wasn't crazy). This is also how it is running on nbuild.