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
       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).

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

       This page is part of release 5.06 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

Linux                             2017-09-15                    GETPEERNAME(2)