socket server Python 服务端如何主动发送消息?

我查看了这里的资料, 看到 server 发送消息都是在 handle 里面也就是说要先有客户端有消息发送过来才会做出对应的发送消息的动作, 那么如果我想在服务端主动的发送消息给客户端这个应该怎么做? https://docs.python.org/3/library/socketserver.html#socketserver.BaseServer.server_bind

这个是实例代码, 这个 handle 里面处理了消息发送的过程。

import socketserver

class MyUDPHandler(socketserver.BaseRequestHandler):
    """
    This class works similar to the TCP handler class, except that
    self.request consists of a pair of data and client socket, and since
    there is no connection the client address must be given explicitly
    when sending data back via sendto().
    """

    def handle(self):
        data = self.request[0].strip()
        socket = self.request[1]
        print("{} wrote:".format(self.client_address[0]))
        print(data)
        socket.sendto(data.upper(), self.client_address)

if __name__ == "__main__":
    HOST, PORT = "localhost", 9999
    with socketserver.UDPServer((HOST, PORT), MyUDPHandler) as server:
        server.serve_forever()