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+.\" Copyright (c) 1983, 1991 The Regents of the University of California.
+.\" All rights reserved.
+.\"
+.\" SPDX-License-Identifier: BSD-4-Clause-UC
+.\"
+.\"     @(#)getpeername.2	6.5 (Berkeley) 3/10/91
+.\"
+.\" Modified Sat Jul 24 16:37:50 1993 by Rik Faith <faith@cs.unc.edu>
+.\" Modified Thu Jul 30 14:37:50 1993 by Martin Schulze <joey@debian.org>
+.\" Modified Sun Mar 28 21:26:46 1999 by Andries Brouwer <aeb@cwi.nl>
+.\" Modified 17 Jul 2002, Michael Kerrisk <mtk.manpages@gmail.com>
+.\"	Added 'socket' to NAME, so that "man -k socket" will show this page.
+.\"
+.TH getpeername 2 2023-04-03 "Linux man-pages 6.05.01"
+.SH NAME
+getpeername \- get name of connected peer socket
+.SH LIBRARY
+Standard C library
+.RI ( libc ", " \-lc )
+.SH SYNOPSIS
+.nf
+.B #include <sys/socket.h>
+.PP
+.BI "int getpeername(int " sockfd ", struct sockaddr *restrict " addr ,
+.BI "                socklen_t *restrict " addrlen );
+.fi
+.SH DESCRIPTION
+.BR getpeername ()
+returns the address of the peer connected to the socket
+.IR sockfd ,
+in the buffer pointed to by
+.IR addr .
+The
+.I addrlen
+argument should be initialized to indicate the amount of space pointed to
+by
+.IR addr .
+On return it contains the actual size of the name returned (in bytes).
+The name is truncated if the buffer provided is too small.
+.PP
+The returned address is truncated if the buffer provided is too small;
+in this case,
+.I addrlen
+will return a value greater than was supplied to the call.
+.SH RETURN VALUE
+On success, zero is returned.
+On error, \-1 is returned, and
+.I errno
+is set to indicate the error.
+.SH ERRORS
+.TP
+.B EBADF
+The argument
+.I sockfd
+is not a valid file descriptor.
+.TP
+.B EFAULT
+The
+.I addr
+argument points to memory not in a valid part of the
+process address space.
+.TP
+.B EINVAL
+.I addrlen
+is invalid (e.g., is negative).
+.TP
+.B ENOBUFS
+Insufficient resources were available in the system
+to perform the operation.
+.TP
+.B ENOTCONN
+The socket is not connected.
+.TP
+.B ENOTSOCK
+The file descriptor
+.I sockfd
+does not refer to a socket.
+.SH STANDARDS
+POSIX.1-2008.
+.SH HISTORY
+POSIX.1-2001, SVr4, 4.4BSD
+(first appeared in 4.2BSD).
+.SH NOTES
+For stream sockets, once a
+.BR connect (2)
+has been performed, either socket can call
+.BR getpeername ()
+to obtain the address of the peer socket.
+On the other hand, datagram sockets are connectionless.
+Calling
+.BR connect (2)
+on a datagram socket merely sets the peer address for outgoing
+datagrams sent with
+.BR write (2)
+or
+.BR recv (2).
+The caller of
+.BR connect (2)
+can use
+.BR getpeername ()
+to obtain the peer address that it earlier set for the socket.
+However, the peer socket is unaware of this information, and calling
+.BR getpeername ()
+on the peer socket will return no useful information (unless a
+.BR connect (2)
+call was also executed on the peer).
+Note also that the receiver of a datagram can obtain
+the address of the sender when using
+.BR recvfrom (2).
+.SH SEE ALSO
+.BR accept (2),
+.BR bind (2),
+.BR getsockname (2),
+.BR ip (7),
+.BR socket (7),
+.BR unix (7)