getpeername man page

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 file 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 file descriptor sockfd does not refer to a socket.

Conforming to

POSIX.1-2001, POSIX.1-2008, SVr4, 4.4BSD (getpeername() first appeared in 4.2BSD).

Notes

For background on the socklen_t type, see 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 4.11 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 https://www.kernel.org/doc/man-pages/.

Referenced By

explain(1), explain(3), explain_getpeername(3), explain_getpeername_or_die(3), getnameinfo(3), getpeereid(3), signal-safety(7), socket(2), socket(7), socketcall(2), syscalls(2), unix(7).

2016-12-12 Linux Programmer's Manual