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