Getsockname returns the current name for the specified socket. The
namelen parameter should be initialized to indicate the amount of space
pointed to by name. On return it contains the actual size of the name
returned (in bytes).
The third argument of getsockname is in reality an `int *' (and this is
what BSD 4.* and libc4 and libc5 have). Some POSIX confusion resulted in the
present socklen_t, also used by glibc. See also accept(2).