'Transmit version/status/date/server, via self._write()'

def send_preamble(self):

    if self.origin_server:
        if self.client_is_modern():
            self._write(('HTTP/%s    %s\r\n' % (self.http_version, self.status)))
            if ('Date' not in self.headers):
                self._write(('Date:    %s\r\n' % http_date()))
            if (self.server_software and ('Server' not in self.headers)):
                self._write(('Server:    %s\r\n' % self.server_software))
    else:
        self._write(('Status:    %s\r\n' % self.status))
