NAME

getpeername — get the name of the peer socket

SYNOPSIS

#include <sys/socket.h>

int getpeername(int socket, struct sockaddr *restrict address,
       socklen_t *restrict address_len);


DESCRIPTION

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 peer 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.

RETURN VALUE

Upon successful completion, 0 shall be returned. Otherwise, -1 shall be returned and errno set to indicate the error.

ERRORS

The getpeername() function shall fail if:

[EBADF]

The socket argument is not a valid file descriptor.

[EINVAL]

The socket has been shut down.

[ENOTCONN]

The socket is not connected or otherwise has not had the peer pre-specified.

[ENOTSOCK]

The socket argument does not refer to a socket.

[EOPNOTSUPP]

The operation is not supported for the socket protocol.

The getpeername() function may fail if:

[ENOBUFS]

Insufficient resources were available in the system to complete the call.

EXAMPLES

None.

APPLICATION USAGE

For AF_UNIX sockets, it is recommended that address points to a buffer of length greater than sizeof(struct sockaddr_un) which has been initialized with null bytes. That way, even if the implementation supports the use of all bytes of sun_path without a terminating null byte, the larger buffer guarantees that the sun_path member can then be passed to other interfaces that expect a null-terminated string. If no truncation occurred based on the input value of address_len, it is unspecified whether the returned address_len will be sizeof(struct sockaddr_un), or merely a value at least as large as offsetof(struct sockaddr_un, sun_path) plus the number of non-null bytes stored in sun_path.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

accept, bind, getsockname, socket

XBD <sys/socket.h>

CHANGE HISTORY

First released in Issue 6. Derived from the XNS, Issue 5.2 specification.

The restrict keyword is added to the getpeername() prototype for alignment with the ISO/IEC 9899:1999 standard.

Issue 7

POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0254 [464] is applied.

Issue 8

Austin Group Defect 561 is applied, adding a paragraph about sun_path to APPLICATION USAGE.

Austin Group Defect 1565 is applied, changing the description of address_len.