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GETPEERNAME(2)              BSD System Calls Manual             GETPEERNAME(2)

NAME
     getpeername -- get name of connected peer

SYNOPSIS
     #include <&lt;sys/socket.h>&gt;

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

DESCRIPTION
     getpeername() returns the address information of the peer connected to
     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.

     getpeername() 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 informa-
     tion 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 con-
     tained 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
     On failure, errno is set to one of the following:

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

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

     [ENOTCONN]         The socket is not connected.

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

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

SEE ALSO
     accept(2), bind(2), getsockname(2), socket(2), getpeereid(3)

STANDARDS
     The getpeername() function conforms to IEEE Std 1003.1-2008
     (``POSIX.1'').

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

BSD                             April 29, 2017                             BSD