---
name: "bindresvport_sa"
section: "3"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/bindresvport"
---

# bindresvport\_sa(3)

bind a socket to a privileged IP port

Part of [bindresvport(3)](/bindresvport/3.md).

## NAME

**bindresvport**, **bindresvport\_sa** – bind a socket to a privileged IP port

## LIBRARY

Standard C Library (libc, -lc)

## 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

The **bindresvport**() and **bindresvport\_sa**() functions are used to bind a socket descriptor to a privileged IP port, that is, a port number in the range 0-1023.

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 an anonymous port (in the range 600-1023) will be chosen, and if [bind(2)](/bind/2.md) is successful, the *sin-\>sin\_port* will be updated to contain the allocated port.

If *sin* is the NULL pointer, an anonymous port will be allocated (as above). However, there is no way for **bindresvport**() to return the allocated port in this case.

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. The **bindresvport\_sa**() function 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

The **bindresvport()** function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

## ERRORS

- \[EPFNOSUPPORT\]

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

The **bindresvport**() function may also fail and set *errno* for any of the errors specified for the calls [bind(2)](/bind/2.md), [getsockopt(2)](/getsockopt/2.md), or [setsockopt(2)](/setsockopt/2.md).

## SEE ALSO

[bind(2)](/bind/2.md), [getsockopt(2)](/getsockopt/2.md), [setsockopt(2)](/setsockopt/2.md), [ip(4)](/ip/4.md)