Question

我有一台带有5个接口的计算机：3个带有公共IP和2个本地IP。我试图将“HELLO”发送到UDP服务器，但我想将接口更改为其中一个本地IP地址。我做了一些研究，这是我需要在python中添加的行：

sock.setsockopt(socket.SOL_IP, socket.IP_MULTICAST_IF, socket.inet_aton("64.195.10.11"))

64.195.10.11是我想要更改为

的IP

所以我的python代码如下所示：

import socket

MCAST_GRP = '224.0.0.1'
MCAST_PORT = 10222

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
sock.setsockopt(socket.SOL_IP, socket.IP_MULTICAST_IF, socket.inet_aton("64.195.10.10"))
sock.sendto("HELLO", (MCAST_GRP, MCAST_PORT))

当我在3个公共IP地址之间切换时，它可以正常工作。但是，如果我在参数中放置了本地IP，则它不起作用（数据包未传递）。我不确定脚本是否未发送，或者服务器是否未收到。发生了什么事？

SL

编辑：我正在用两种方式听：

import socket
import sys

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.bind(("", 10222))
sock.setsockopt(socket.IPPROTO_IP,
                                 socket.IP_ADD_MEMBERSHIP,
                                 socket.inet_aton("224.0.0.1") +
                                 socket.inet_aton("64.195.10.11"))
sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_LOOP, 0)

while True:
    print >>sys.stderr, '\nwaiting to receive message'
    data, address = sock.recvfrom(1024)

    print >>sys.stderr, 'received %s bytes from %s' % (len(data), address)
    print >>sys.stderr, data

    print >>sys.stderr, 'sending acknowledgement to', address
    sock.sendto('ack', address)

并使用twisted：

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

class MulticastServerUDP(DatagramProtocol):
    def __init__ (self, group, name):
        self.group = group
        self.name = name
    def startProtocol(self):
        print '%s Started Listening' % self.group
        self.transport.joinGroup(self.group)

    def datagramReceived(self, datagram, address):
        print "%s Received:"%self.name + repr(datagram) + repr(address)

reactor.listenMulticast(10222, MulticastServerUDP('224.0.0.1', 'SERVER1'), listenMultiple = True)             
reactor.run()

Answer 1

如果服务器和客户端在同一台机器上（用于测试），可能需要像这样设置IP_MULTICAST_LOOP选项（c代码）：

int loop_on = 1;
setsockopt(socket, IPPROTO_IP, IP_MULTICAST_LOOP, &loop_on, sizeof(loop_on));

在python中你可以试试这样的东西：

sock.setsockopt(socket.SOL_IP, socket.IP_MULTICAST_LOOP, 1)

希望得到这个帮助。

编辑：添加一些跟踪（来自我的Linux框）

我使用的代码与SquallLeohart发布的代码相同：

#! /usr/bin/python

import socket

MCAST_GRP = '224.0.0.1'
MCAST_PORT = 10222

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
sock.setsockopt(socket.SOL_IP, socket.IP_MULTICAST_IF, socket.inet_aton("192.168.1.7"))
sock.sendto("HELLO", (MCAST_GRP, MCAST_PORT))

和

#! /usr/bin/python
import socket
import sys

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.bind(("", 10222))
sock.setsockopt(socket.IPPROTO_IP,
                                 socket.IP_ADD_MEMBERSHIP,
                                 socket.inet_aton("224.0.0.1") +
                                 socket.inet_aton("192.168.1.7"))
sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_LOOP, 0)

while True:
    print >>sys.stderr, '\nwaiting to receive message'
    data, address = sock.recvfrom(1024)

    print >>sys.stderr, 'received %s bytes from %s' % (len(data), address)
    print >>sys.stderr, data

    print >>sys.stderr, 'sending acknowledgement to', address
    sock.sendto('ack', address)

我得到了这个输出：

waiting to receive message
received 5 bytes from ('192.168.1.7', 43761)
HELLO
sending acknowledgement to ('192.168.1.7', 43761)

waiting to receive message
received 5 bytes from ('192.168.1.7', 52326)
HELLO
sending acknowledgement to ('192.168.1.7', 52326)

waiting to receive message

使用tcpdump：

21:01:33.814728 IP localhost.localdomain.34956 > all-systems.mcast.net.10222: UDP, length 5
21:01:35.364605 IP localhost.localdomain.39078 > all-systems.mcast.net.10222: UDP, length 5
21:01:36.228477 IP localhost.localdomain.49926 > all-systems.mcast.net.10222: UDP, length 5

问候。

Answer 2

答案是：我的防火墙不接受来自该RFC1918 IP地址的udp数据包。

如何更改套接字的IP_MULTICAST_IF

2 个答案: