quo; while waiting for
input and will return a pair, normally comprising as its car a
bytevector of length &rsquo;size&rsquo; containing the data, and as its cdr the
number of bytes received (which will be the same as &rsquo;size&rsquo; unless an
end-of-file object was encountered part way through receiving the
data).  The event loop will not be blocked by this procedure even if
only individual bytes are available at any one time (although if
&rsquo;port&rsquo; references a socket, it should be non-blocking