e event loop
will not be blocked by this procedure even if only individual
characters or part characters are available at any one time (although
if &rsquo;port&rsquo; references a socket, it should be non-blocking for this to
be guaranteed).  It is intended to be called in a waitable procedure
invoked by a-sync, and this procedure is implemented using
a-sync-glib-read-watch.  If an end-of-file object is encountered which
terminates a line of text, a string containing the line of text will
be returned (and f