int getpeername(int socket, struct sockaddr *restrictaddress,
The getpeername() function shall retrieve the peer address of
the specified socket, store this address in the
sockaddr structure pointed to by the address argument,
and store the length of this address in the object pointed to
by the address_len argument.
If the actual length of the address is greater than the length of
the supplied sockaddr structure, the stored address
shall be truncated.
If the protocol permits connections by unbound clients, and the peer
is not bound, then the value stored in the object pointed
to by address is unspecified.
Upon successful completion, 0 shall be returned. Otherwise, -1 shall
be returned and errno set to indicate the error.
The getpeername() function shall fail if:
The socket argument is not a valid file descriptor.
The socket has been shut down.
The socket is not connected or otherwise has not had the peer pre-specified.
The socket argument does not refer to a socket.
The operation is not supported for the socket protocol.
The getpeername() function may fail if:
Insufficient resources were available in the system to complete the
The following sections are informative.
accept() , bind() , getsockname() , socket()
, the Base Definitions volume of
IEEE Std 1003.1-2001, <sys/socket.h>
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at