getpeername(2) — Linux manual page


getpeername(2)             System Calls Manual            getpeername(2)

NAME         top

       getpeername - get name of connected peer socket

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <sys/socket.h>

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

DESCRIPTION         top

       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         top

       On success, zero is returned.  On error, -1 is returned, and
       errno is set to indicate the error.

ERRORS         top

       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.

STANDARDS         top


HISTORY         top

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

NOTES         top

       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         top

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

COLOPHON         top

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Linux man-pages 6.9.1          2024-05-02                 getpeername(2)

Pages that refer to this page: socket(2)socketcall(2)syscalls(2)getnameinfo(3)sockaddr(3type)crypttab(5)systemd.exec(5)signal-safety(7)socket(7)unix(7)