On Unix wait-for-input-available is just an interface into
the select() function.   The description of the function 
using read-char and read-byte is just a way of describing
its behavior in Common Lisp terms (and sockets aren't part of Common Lisp).
 
 If you've got an fd for a socket on which you expect a connection you can
also use wait-for-input-available.   

 If you're encountering problems doing this, please send a message
to <franz.com at bugs> so we can go through the process of getting
all the information we need about your particular version of lisp
so that we can help you get it up and running.