sockaddr(3type)                                                sockaddr(3type)

NAME
       sockaddr, sockaddr_storage, socklen_t - socket address

LIBRARY
       Standard C library (libc)

SYNOPSIS
       #include <sys/socket.h>

       struct sockaddr {
           sa_family_t     sa_family;      /* Address family */
           char            sa_data[];      /* Socket address */
       };

       struct sockaddr_storage {
           sa_family_t     ss_family;      /* Address family */
       };

       typedef /* ... */ socklen_t;
       typedef /* ... */ sa_family_t;


DESCRIPTION
       sockaddr
              Describes a socket address.

       sockaddr_storage
              A structure at least as large as any other sockaddr_* address
              structures.  It's aligned so that a pointer to it can be cast as
              a pointer to other sockaddr_* structures and used to access its
              fields.

       socklen_t
              Describes the length of a socket address.  This is an integer
              type of at least 32 bits.

       sa_family_t
              Describes a socket's protocol family.  This is an unsigned
              integer type.

   Internet domain sockets
       See sockaddr_in(3type) and sockaddr_in6(3type).

   UNIX domain sockets
       See sockaddr_un(3type).

STANDARDS
       POSIX.1-2024.

HISTORY
       POSIX.1-2001.

       socklen_t was invented by POSIX.  See also accept(2).

       These structures were invented before modern ISO C strict-aliasing
       rules.  If aliasing rules are applied strictly, these structures would
       be extremely difficult to use without invoking undefined behavior.
       POSIX.1-2024 fixed this by requiring that implementations make sure
       that these structures can be safely used as they were designed.

NOTES
       socklen_t is also defined in <netdb.h>.

       sa_family_t is also defined in <netinet/in.h> and <sys/un.h>.

SEE ALSO
       accept(2), bind(2), connect(2), getpeername(2), getsockname(2),
       getsockopt(2), sendto(2), setsockopt(2), socket(2), socketpair(2),
       getaddrinfo(3), gethostbyaddr(3), getnameinfo(3), htonl(3), ipv6(7),
       socket(7)

Linux man-pages 6.17              2026-02-08                   sockaddr(3type)