code: private CharSequence hostInvocation()
      throws IOException
    {
      if (_host != null) {
      }
      else if (_uriHost.length() > 0) {
        _host = _uriHost;
      }
      else if ((_host = getForwardedHostHeader()) != null) {
      }
      else if ((_host = getHostHeader()) != null) {
      }
      else if (HTTP_1_1 <= version()) {
        throw new BadRequestException(L.l("HTTP/1.1 requires a Host header (Remote IP={0})", 
                                          connTcp().ipRemote()));
      }
  
      return _host;
    }
docs: Returns the virtual host from the invocation