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GETPEERNAME(2)                System Calls Manual               GETPEERNAME(2)

NAME
     getpeername - get name of connected peer

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <sys/socket.h>

     int
     getpeername(int s, struct sockaddr * restrict name,
         socklen_t * restrict namelen);

DESCRIPTION
     The getpeername() function returns the name of the peer connected to the
     socket s.  One common use occurs when a process inherits an open socket,
     such as TCP servers forked from inetd(8).  In this scenario,
     getpeername() is used to determine the connecting client's IP address.

     The function takes three parameters:

           s        contains the file descriptor of the socket whose peer
                    should be looked up.

           name     points to a sockaddr structure that will hold the address
                    information for the connected peer.  Normal use requires
                    one to use a structure specific to the protocol family in
                    use, such as sockaddr_in (IPv4) or sockaddr_in6 (IPv6),
                    cast to a (struct sockaddr *).

                    For greater portability, especially with the newer
                    protocol families, the new struct sockaddr_storage should
                    be used.  sockaddr_storage is large enough to hold any of
                    the other sockaddr_* variants.  On return, it can be cast
                    to the correct sockaddr type, based on the protocol family
                    contained in its ss_family field.

           namelen  indicates the amount of space pointed to by name, in
                    bytes.

     If address information for the local end of the socket is required, the
     getsockname(2) function should be used instead.

     If name does not point to enough space to hold the entire socket address,
     the result will be truncated to namelen bytes.

RETURN VALUES
     If the call succeeds, a 0 is returned and namelen is set to the actual
     size of the socket address returned in name.  Otherwise, errno is set and
     a value of -1 is returned.

ERRORS
     The call succeeds unless:

     [EBADF]            The argument s is not a valid descriptor.

     [EFAULT]           The name parameter points to memory not in a valid
                        part of the process address space.

     [ENOBUFS]          Insufficient resources were available in the system to
                        perform the operation.

     [ENOTCONN]         The socket is not connected.

     [ENOTSOCK]         The argument s is a file, not a socket.

SEE ALSO
     accept(2), bind(2), getsockname(2), socket(2)

STANDARDS
     The function conforms to IEEE Std 1003.1-2008 ("POSIX.1").

HISTORY
     The getpeername() function call appeared in 4.2BSD.

NetBSD 10.99                     June 3, 2011                     NetBSD 10.99