anchor.diff:  
   (in-package :net.sockets)
   
  -(defun create-socket (family type connect external-format)
  +(defun create-socket (family type connect external-format &optional fd)
     (make-instance (select-socket-class family type connect :default)
  -                 :family family
  +                 :family family :file-descriptor fd
                    :external-format external-format))
   
   (defmacro with-close-on-error ((var value) &body body)
  
positive.code: ACCEPT-CONNECTION and BODY is executed as implicit PROGN.  The socket
  is automatically closed upon exit."
    `(with-open-stream (,var (accept-connection ,passive-socket ,@args)) ,@body))
  
  (defun get-socket-family-from-fd (fd)
    (with-sockaddr-storage (ss)
      (with-socklen (size size-of-sockaddr-storage)
        (getsockname fd ss size)
  
negative.code: an invalid socket descriptor and `ERRORP' is not NIL a condition subtype of POSIX-ERROR
  is signaled, otherwise two values are returned: NIL and the specific condition object."
    (flet ((%make-socket-stream ()
             (let ((family (switch ((get-address-family fd) :test #'=)
                             (af-inet :ipv4)
                             (af-inet6 :ipv6)
                             (af-local :local))))
               (create-socket family :stream :active external-format fd))))
      (if errorp
          (%make-socket-stream)
          (ignore-some-conditions (posix-error)
  