.\"	$OpenBSD: bindresvport.3,v 1.6 1997/07/01 17:42:03 dm Exp $
.\"
.Dd November 22, 1987
.Dt BINDRESVPORT 3
.Os
.Sh NAME
.Nm bindresvport
.Nd bind a socket to a privileged IP port
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <netinet/in.h>
.Ft int
.Fn bindresvport "int sd" "struct sockaddr_in *sin"
.Sh DESCRIPTION
.Fn bindresvport
is used to bind a socket descriptor to a privileged
.Tn IP
port, that is, a
port number in the range 0-1023.
The routine returns 0 if it is successful,
otherwise -1 is returned and
.Va errno
set to reflect the cause of the error.
.Pp
Only root can bind to a privileged port; this call will fail for any
other users.
.Pp
If the value of sin->sin_port is non-zero
.Fn bindresvport
otherwise it attempts to use the specified port.  If that fails, it
chooses another privileged port number automatically.