getpeername(2) System Calls Manual getpeername(2)
NAME
getpeername - get name of connected peer socket
LIBRARY
Standard C library (libc, -lc)
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.
STANDARDS
POSIX.1-2008.
HISTORY
POSIX.1-2001, SVr4, 4.4BSD (first appeared in 4.2BSD).
NOTES
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 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 informa-
tion (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 man-pages 6.9.1 2024-05-02 getpeername(2)
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