getpeername(2) - Linux manual page (original) (raw)
getpeername(2) System Calls Manual getpeername(2)
NAME top
getpeername - get name of connected peer socketLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS top
**#include <sys/socket.h>**
**int getpeername(int** _sockfd_**, struct sockaddr *restrict** _addr_**,**
**socklen_t *restrict** _addrlen_**);**DESCRIPTION top
**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 top
On success, zero is returned. On error, -1 is returned, and _[errno](../man3/errno.3.html)_
is set to indicate the error.ERRORS top
**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 top
POSIX.1-2008.HISTORY top
POSIX.1-2001, SVr4, 4.4BSD (first appeared in 4.2BSD).NOTES top
For stream sockets, once a [connect(2)](../man2/connect.2.html) 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)](../man2/connect.2.html) on a datagram socket merely sets the peer
address for outgoing datagrams sent with [write(2)](../man2/write.2.html) or [recv(2)](../man2/recv.2.html). The
caller of [connect(2)](../man2/connect.2.html) 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)](../man2/connect.2.html) 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)](../man2/recvfrom.2.html).SEE ALSO top
[accept(2)](../man2/accept.2.html), [bind(2)](../man2/bind.2.html), [getsockname(2)](../man2/getsockname.2.html), [ip(7)](../man7/ip.7.html), [socket(7)](../man7/socket.7.html), [unix(7)](../man7/unix.7.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-07-23 getpeername(2)
Pages that refer to this page:socket(2), socketcall(2), syscalls(2), getnameinfo(3), sockaddr(3type), crypttab(5), systemd.exec(5), signal-safety(7), socket(7), unix(7)