proc unique_port
{
  # Try to find an unused port number for each running instance of the program.

  global START := '8192'
  global RANGE := $($(awk '{print $1}' /proc/sys/net/ipv4/ip_local_port_range)-)
  if test $RANGE -lt 8
  {
    global START := $($[awk '{print $2}' /proc/sys/net/ipv4/ip_local_port_range])
    global RANGE := $(65535-)
    if test $RANGE -lt 8
    {
      global START := '16384'
      global RANGE := '32768'
    }
  }
  echo $(($$%$RANGE)+)
}