  void update_hostname(const char *host_arg)
  {
    hostname=(char*) host_arg;     // This will not be modified!
    hostname_length= hostname ? strlen( hostname ) : 0;
    if (!host_arg ||
        (!(host_arg=(char*) calc_ip(host_arg,&ip,'/')) ||
         !(host_arg=(char*) calc_ip(host_arg+1,&ip_mask,'\0'))))
    {
      ip= ip_mask=0;               // Not a masked ip
    }
  }
  void update_hostname(const char *host_arg)
  {
    hostname=(char*) host_arg;      
    hostname_length= hostname ? strlen( hostname ) : 0;
    if (!host_arg ||
        (!(host_arg=(char*) calc_ip(host_arg,&ip,'/')) ||
         !(host_arg=(char*) calc_ip(host_arg+1,&ip_mask,'\0'))))
    {
      ip= ip_mask=0;                
    }
  }