getpeername(2) [netbsd man page]

GETPEERNAME(2)						      BSD System Calls Manual						    GETPEERNAME(2)

NAME

     getpeername -- get name of connected peer

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <sys/socket.h>

     int
     getpeername(int s, struct sockaddr * restrict name, socklen_t * restrict namelen);

DESCRIPTION

     The getpeername() function returns the name of the peer connected to the socket s.  One common use occurs when a process inherits an open
     socket, such as TCP servers forked from inetd(8).	In this scenario, getpeername() is used to determine the connecting client's IP address.

     The function takes three parameters:

	   s	    contains the file descriptor of the socket whose peer should be looked up.

	   name     points to a sockaddr structure that will hold the address information for the connected peer.  Normal use requires one to use
		    a structure specific to the protocol family in use, such as sockaddr_in (IPv4) or sockaddr_in6 (IPv6), cast to a (struct sock-
		    addr *).

		    For greater portability, especially with the newer protocol families, the new struct sockaddr_storage should be used.
		    sockaddr_storage is large enough to hold any of the other sockaddr_* variants.  On return, it can be cast to the correct sock-
		    addr type, based on the protocol family contained in its ss_family field.

	   namelen  indicates the amount of space pointed to by name, in bytes.

     If address information for the local end of the socket is required, the getsockname(2) function should be used instead.

     If name does not point to enough space to hold the entire socket address, the result will be truncated to namelen bytes.

RETURN VALUES

     If the call succeeds, a 0 is returned and namelen is set to the actual size of the socket address returned in name.  Otherwise, errno is set
     and a value of -1 is returned.

ERRORS

     The call succeeds unless:

     [EBADF]		The argument s is not a valid descriptor.

     [EFAULT]		The name parameter points to memory not in a valid part of the process address space.

     [ENOBUFS]		Insufficient resources were available in the system to perform the operation.

     [ENOTCONN] 	The socket is not connected.

     [ENOTSOCK] 	The argument s is a file, not a socket.

SEE ALSO

     accept(2), bind(2), getsockname(2), socket(2)

STANDARDS

     The function conforms to IEEE Std 1003.1-2008 (``POSIX.1'').

HISTORY

     The getpeername() function call appeared in 4.2BSD.

BSD
								   June 3, 2011 							       BSD

GETPEERNAME(2)						     Linux Programmer's Manual						    GETPEERNAME(2)

NAME

       getpeername - get name of connected peer socket

SYNOPSIS

       #include <sys/socket.h>

       int getpeername(int sockfd, struct sockaddr *addr, socklen_t *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 appropriately.

ERRORS

       EBADF  The argument sockfd is not a valid 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 argument sockfd is a file, not a socket.

CONFORMING TO

       SVr4, 4.4BSD (the getpeername() function call first appeared in 4.2BSD), POSIX.1-2001.

NOTES

       The third argument of getpeername() is in reality an int * (and this is what 4.x BSD and libc4  and  libc5  have).   Some  POSIX  confusion
       resulted in the present socklen_t, also used by glibc.  See also accept(2).

       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 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) 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)

COLOPHON

       This page is part of release 3.53 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2013-02-12							    GETPEERNAME(2)