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GETSOCKNAME(2)                System Calls Manual               GETSOCKNAME(2)

     getsockname - get socket name

     Standard C Library (libc, -lc)

     #include <sys/socket.h>

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

     getsockname() returns the locally bound address information for a
     specified socket.

     Common uses of this function are as follows:

        When bind(2) is called with a port number of 0 (indicating the kernel
         should pick an ephemeral port) getsockname() is used to retrieve the
         kernel-assigned port number.

        When a process calls bind(2) on a wildcard IP address, getsockname()
         is used to retrieve the local IP address for the connection.

        When a function wishes to know the address family of a socket,
         getsockname() can be used.

     getsockname() takes three parameters:

     s, Contains the file descriptor for the socket to be looked up.

     name points to a sockaddr structure which will hold the resulting address
     information.  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 sockaddr *).

     For greater portability (such as newer protocol families) the new
     structure sockaddr_storage exists.  sockaddr_storage is large enough to
     hold any of the other sockaddr_* variants.  On return, it should be cast
     to the correct sockaddr type, according to the current protocol family.

     namelen indicates the amount of space pointed to by name, in bytes.  Upon
     return, namelen is set to the actual size of the returned address

     If the address of the destination socket for a given socket connection is
     needed, the getpeername(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.

     On success, getsockname() returns a 0, 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.

     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.

     [EINVAL]           The socket has been shut down.

     [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.

     bind(2), socket(2)

     The getsockname() function call appeared in 4.2BSD.

NetBSD 10.99                     July 30, 2016                    NetBSD 10.99