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GETPEERNAME(2) Linux Programmer's Manual GETPEERNAME(2)
NAME
getpeername - get name of connected peer socket
SYNOPSIS
#include <sys/socket.h>
int getpeername(int sockfd, struct sockaddr *addr, socklen_t *addrlen);
DESCRIPTION
getpeername() returns the address of the peer connected to the socket sockfd, in the buf‐
fer pointed to by addr. The addrlen argument should be initialized to indicate the amount
of space pointed to by 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.
The returned address is truncated if the buffer provided is too small; in this case,
addrlen will return a value greater than was supplied to the call.
RETURN VALUE
On success, zero is returned. On error, -1 is returned, and errno is set appropriately.
ERRORS
EBADF The argument sockfd is not a valid descriptor.
EFAULT The addr argument points to memory not in a valid part of the process address
space.
EINVAL addrlen is invalid (e.g., is negative).
ENOBUFS
Insufficient resources were available in the system to perform the operation.
ENOTCONN
The socket is not connected.
ENOTSOCK
The argument sockfd is a file, not a socket.
CONFORMING TO
SVr4, 4.4BSD (the getpeername() function call first appeared in 4.2BSD), POSIX.1-2001.
NOTES
The third argument of getpeername() is in reality an int * (and this is what 4.x BSD and
libc4 and libc5 have). Some POSIX confusion resulted in the present socklen_t, also used
by glibc. See also accept(2).
For stream sockets, once a connect(2) has been performed, either socket can call getpeer‐
name() to obtain the address of the peer socket. On the other hand, datagram sockets are
connectionless. Calling connect(2) on a datagram socket merely sets the peer address for
outgoing datagrams sent with write(2) or recv(2). The caller of connect(2) can use get‐
peername() to obtain the peer address that it earlier set for the socket. However, the
peer socket is unaware of this information, and calling getpeername() on the peer socket
will return no useful information (unless a 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 recvfrom(2).
SEE ALSO
accept(2), bind(2), getsockname(2), ip(7), socket(7), unix(7)
COLOPHON
This page is part of release 3.74 of the Linux man-pages project. A description of the
project, information about reporting bugs, and the latest version of this page, can be
found at http://www.kernel.org/doc/man-pages/.
Linux 2013-02-12 GETPEERNAME(2)
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