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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 *restrict addr,
socklen_t *restrict 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 to indicate the error.
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 infor‐
mation, 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)
Linux 2021-03-22 GETPEERNAME(2)