is procedure will
start a read watch in the event loop passed in as an argument, or if
none is passed (or #f is passed), in the default event loop.  The
&rsquo;proc&rsquo; callback should take a single argument, and when called this
will be set to &rsquo;in or &rsquo;excpt.  The same port or file descriptor can
also be passed to event-loop-add-write-watch, and if so and the
descriptor is also available for writing, the write callback will also
be called with its argument set to &rsquo;out.  If there is alre