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 buffer 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 getpeername() 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 getpeername() 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 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 2013-02-12 GETPEERNAME(2)