.\" Copyright (c) 1983, 1991 The Regents of the University of California. .\" All rights reserved. .\" .\" %%%LICENSE_START(BSD_4_CLAUSE_UCB) .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" %%%LICENSE_END .\" .\" @(#)getpeername.2 6.5 (Berkeley) 3/10/91 .\" .\" Modified Sat Jul 24 16:37:50 1993 by Rik Faith .\" Modified Thu Jul 30 14:37:50 1993 by Martin Schulze .\" Modified Sun Mar 28 21:26:46 1999 by Andries Brouwer .\" Modified 17 Jul 2002, Michael Kerrisk .\" Added 'socket' to NAME, so that "man -k socket" will show this page. .\" .TH GETPEERNAME 2 2017-09-15 "Linux" "Linux Programmer's Manual" .SH NAME getpeername \- get name of connected peer socket .SH SYNOPSIS .B #include .PP .BI "int getpeername(int " sockfd ", struct sockaddr *" addr \ ", socklen_t *" addrlen ); .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 appropriately. .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 CONFORMING TO POSIX.1-2001, POSIX.1-2008, SVr4, 4.4BSD .RB ( getpeername () first appeared in 4.2BSD). .SH NOTES For background on the .I socklen_t type, see .BR accept (2). .PP 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) .SH COLOPHON This page is part of release 4.16 of the Linux .I man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/.