anchor.diff:  
   (defparameter *echo-address* (ensure-address #(127 0 0 1)))
   (defparameter *echo-port* 7)
  +(defparameter *echo-timeout* 2)
   
   ;;;; Addresses
   
  
positive.code: (test simple-udp-client.2
    (is-true
     (with-open-socket (s :type :datagram :address-family :ipv4)
       (send-to s #(1 2 3 4 5)
                :remote-host *echo-address*
                :remote-port *echo-port*)
  
negative.code:   (is-true
     (with-open-socket (s :remote-host *echo-address* :remote-port *echo-port*
                          :type :datagram :address-family :ipv4)
       (setf (socket-option s :receive-timeout) *echo-timeout*)
       (send-to s #(1 2 3 4 5))
       (let ((nbytes (nth-value 1 (receive-from s :size 200))))
         (plusp nbytes)))))
  