% Copyright (c) 1988 Massachusetts Institute of Technology
%	$Source: /mit/zephyr/repository/zephyr/doc/progman/own-socket.tex,v $
%	$Author: jtkohl $
%	$Header: /mit/zephyr/repository/zephyr/doc/progman/own-socket.tex,v 2.0 1989/04/05 15:55:09 jtkohl Exp $
%
\subsection{Using Your Own Socket}
\label{own-socket}

Applications normally use the socket which is bound
by ZOpenPort.  However, in some cases it may be desirable to
make the \Zephyr\ library to use a socket that the application has
already bound.  The following functions facilitate this.

\subsubsection{ZGetFD}
\label{ZGetFD}

\template{int}{ZGetFD}{}
\etemplate
\prereq{ZInitialize or ZSetFD}
\errors{-1 = No current file descriptor}

The ZGetFD function returns file descriptor that the
\Zephyr\ library is currently using for the bound socket.  If no file
descriptor has been assigned yet, -1 is returned.

\subsubsection{ZSetFD}
\label{ZSetFD}

\template{Code_t}{ZSetFD}{fd}
\tline{int}{fd}
\etemplate
\prereq{None}
\errors{None}

The ZSetFD function first closes any port that was opened by ZOpenPort
(\myref{ZOpenPort}) and then sets the file descriptor that the
\Zephyr\ library will use for all communication to {\bf fd}.  This may
be useful in an application that needs to open and perform operations
on its own port ({\it e.g.\/} binding a specific port number) before making it
available to the \Zephyr\ library.