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# getsockname

    GETSOCKNAME(2)                System Calls Manual               GETSOCKNAME(2)

    NAME
         getsockname - get socket name

    SYNOPSIS
         #include <sys/types.h>
         #include <sys/socket.h>

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

    DESCRIPTION
         getsockname() returns the locally bound address information for a speci-
         fied socket.

         Common uses of this function are as follows:

         o   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.

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

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

         getsockname() takes three parameters:

         s, Contains the file desriptor 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 struc-
         ture 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 infor-
         mation.

         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.

    RETURN VALUES
         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.

    ERRORS
         If getsockname() fails, errno is set to one of the following:

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

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

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

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

    SEE ALSO
         accept(2), bind(2), getpeername(2), getpeereid(2), socket(2)

    BUGS
         Names bound to sockets in the UNIX domain are inaccessible; getsockname
         returns a zero length name.

    HISTORY
         The getsockname() function call appeared in 4.2BSD.

    BSD                              July 17, 1999                             BSD

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