BINDRESVPORT(3)

NAME
bindresvport, bindresvport_sa - bind a socket to a reserved privileged IP port

LIBRARY
libc

SYNOPSIS
#include <sys/types.h>
#include <rpc/rpc.h>
int
bindresvport(int sd, struct sockaddr_in *sin);
int
bindresvport_sa(int sd, struct sockaddr *sa);

DESCRIPTION
bindresvport() and bindresvport_sa() are used to bind a socket descriptor to a reserved privileged 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 errno set to reflect the cause of the error.

If sin is a pointer to a struct sockaddr_in then the appropriate fields in the structure should be defined. Note that sin->sin_family must be initialized to the address family of the socket, passed by sd. If sin->sin_port is ‘0’ then a port (in the range 600-1023) will be chosen, and if bind(2) is successful, the sin->sin_port will be updated to contain the allocated port.

If sin is the NULL pointer, a port will be allocated (as above). However, there is no way for bindresvport() to return the allocated port in this case. getsockname(2) can be used to determine the assigned port.

Only root can bind to a privileged port; this call will fail for any other users.

Function prototype of bindresvport() is biased to AF_INET socket. bindresvport_sa() acts exactly the same, with more neutral function prototype. Note that both functions behave exactly the same, and both support AF_INET6 sockets as well as AF_INET sockets.

RETURN VALUES
If the bind is successful, a 0 value is returned. A return value of -1 indicates an error, which is further specified in the global errno.

ERRORS

[EPFNOSUPPORT]
    If second argument was supplied, and address family did not match between arguments.

bindresvport() may also fail and set errno for any of the errors specified for the calls bind(2), getsockopt(2), or setsockopt(2).

SEE ALSO
bind(2), getsockname(2), getsockopt(2), setsockopt(2), ip(4)