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.\"     @(#)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 2017-09-15 "Linux" "Linux Programmer's Manual"

.SH NAME

getpeername \- get name of connected peer socket

.SH SYNOPSIS

.B #include <sys/socket.h>

.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 4.15 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/.