 at any one
time.  It is intended to be called within a waitable procedure invoked
by a-sync (which supplies the &rsquo;await&rsquo; and &rsquo;resume&rsquo; arguments), and
this procedure is implemented using await-put-bytevector!.  If an
exceptional condition (&rsquo;excpt) is encountered, #f will be returned,
otherwise #t will be returned (but an exceptional condition should
never be encountered on an output port).  The &rsquo;loop&rsquo; argument is
optional: this procedure operates on the event loop pa