This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.
#include <sys/socket.h> int getpeername(int socket, struct sockaddr *restrict address, socklen_t *restrict address_len);
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.
The address_len argument points to a socklen_t object which on input specifies the length of the supplied sockaddr structure, and on output specifies the length of the stored address. 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 call.
The following sections are informative.
accept(), bind(), getsockname(), socket()
The Base Definitions volume of POSIX.1-2017, <sys_socket.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .