扭曲的Python:UDP广播(简单的回声服务器)

Question

我正在尝试使用Python Twisted - UDP示例来使用UDP广播.我可以从客户端发送消息并在服务器上接收它,但是,它不会发回消息.

客户:

from twisted.internet.protocol import DatagramProtocol
from twisted.internet import reactor

from socket import SOL_SOCKET, SO_BROADCAST

class EchoClientDatagramProtocol(DatagramProtocol):
    strings = [
        "Hello, world!",
        "What a fine day it is.",
        "Bye-bye!"
    ]

    def startProtocol(self):
        self.transport.socket.setsockopt(SOL_SOCKET, SO_BROADCAST, True)
        self.transport.connect("255.255.255.255", 8000)
        self.sendDatagram()

    def sendDatagram(self):
        if len(self.strings):
            datagram = self.strings.pop(0)
            self.transport.write(datagram)
        else:
            reactor.stop()

    def datagramReceived(self, datagram, host):
        print 'Datagram received: ', repr(datagram)
        self.sendDatagram()

def main():
    protocol = EchoClientDatagramProtocol()
    #0 means any port
    t = reactor.listenUDP(0, protocol)
    reactor.run()

if __name__ == '__main__':
   main()

服务器:

from twisted.internet.protocol import DatagramProtocol
from twisted.internet import reactor

class EchoUDP(DatagramProtocol):
    def datagramReceived(self, datagram, address):
        print "Received from address: " + str(address)
        print str(datagram)
        self.transport.write(datagram, address)
        print "Finished sending reply."

print "Starting server."
reactor.listenUDP(8000, EchoUDP())
reactor.run()

控制台输出:

Server:

Starting server.
Received from address ('192.168.1.137', 53737)
Hello, world!
Finished sending reply.

Client:

no output.

Answer 1

transport.connect创建一个已连接的 UDP 套接字

连接的 UDP 套接字与标准套接字略有不同 - 它只能向/从单个地址发送和接收数据报，但这并不意味着连接。数据报仍可能以任何顺序到达，并且另一侧的端口可能没有人监听。连接的 UDP 套接字的好处是它可以提供未传送包的通知。这取决于许多因素，几乎所有因素都超出了应用程序的控制范围，但它仍然提供了某些偶尔有用的好处。

我怀疑客户端没有捕获服务器的响应，因为它正在侦听来自广播地址的响应，而不是服务器的特定地址。

相反，只需使用self.transport.write(data, (host, port))write 的形式，而不先启动连接 - 这将允许客户端从任何地址接收数据包。

from twisted.internet.protocol import DatagramProtocol
from twisted.internet import reactor

from socket import SOL_SOCKET, SO_BROADCAST

class EchoClientDatagramProtocol(DatagramProtocol):
    strings = [
        "Hello, world!",
        "What a fine day it is.",
        "Bye-bye!"
    ]

    def startProtocol(self):
        self.transport.socket.setsockopt(SOL_SOCKET, SO_BROADCAST, True)
        #self.transport.connect("255.255.255.255", 8000) <- not needed
        self.sendDatagram()

    def sendDatagram(self):
        if len(self.strings):
            datagram = self.strings.pop(0)
            self.transport.write(datagram, ('255.255.255.255', 8000)) # <- write to broadcast address here
        else:
            reactor.stop()

    def datagramReceived(self, datagram, host):
        print 'Datagram received: ', repr(datagram)
        self.sendDatagram()

def main():
    protocol = EchoClientDatagramProtocol()
    #0 means any port
    t = reactor.listenUDP(0, protocol)
    reactor.run()


if __name__ == '__main__':
   main()