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

       getpeername - get name of connected peer socket

       #include <sys/socket.h>

       int getpeername(int sockfd, struct sockaddr *addr, socklen_t *addrlen);

       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.

       On  success,  zero is returned.	On error, -1 is returned, and errno is
       set appropriately.

       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).

	      Insufficient  resources  were available in the system to perform
	      the operation.

	      The socket is not connected.

	      The file descriptor sockfd does not refer to a socket.

       POSIX.1-2001, POSIX.1-2008, SVr4, 4.4BSD (getpeername() first  appeared
       in 4.2BSD).

       For background on the socklen_t type, see 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 con-
       nect(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).

       accept(2), bind(2), getsockname(2), ip(7), socket(7), unix(7)

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       description of the project, information about reporting bugs,  and  the
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Linux				  2016-12-12			GETPEERNAME(2)