...
       For IP  only  one  socket  may  be
       bound  to  a  specific  local address/port pair. For TCP a
       bound  local  socket  endpoint  (address/port   pair)   is
       unavailable for some time after closing the socket, unless
       the SO_REUSEADDR flag is set. Note that carelessly setting
       SO_REUSEADDR might make TCP more unreliable unless PAWS is
       used (see tcp(4)); the delay is needed to handle old pack-
       ets still in the network.
       ...