def listen(self, *, host, port, override=False, forever=False, **kwargs):
        """Listen on TCP/IP socket.

        Parameters
        ----------
        host: str
            Host like '127.0.0.1'
        port:
            Port like 80.
        """
        if override:
            argv = dict(enumerate(sys.argv))
            host = argv.get(1, host)
            port = int(argv.get(2, port))
        server = self.loop.create_server(
            self.__handler.fork, host, port, **kwargs)
        server = self.loop.run_until_complete(server)
        self.log('info',
            'Start listening host="{host}" port="{port}"'.
            format(host=host, port=port))
        if forever:
            try:
                self.loop.run_forever()
            except KeyboardInterrupt:
                pass
        return server