英文:
Golang doesn't send UDP packet to multicast group
问题
目前我正在尝试用Go重新实现一个C应用程序。C应用程序的一部分是将字符串发送到多播组。这会通过tcpdump捕获以下数据包：
00000000 d4 c3 b2 a1 02 00 04 00 00 00 00 00 00 00 00 00 |................|
00000010 ff ff 00 00 01 00 00 00 14 81 06 56 47 2c 01 00 |...........VG,..|
00000020 46 00 00 00 46 00 00 00 33 33 00 02 10 01 04 ce |F...F...33......|
00000030 ef ca fe 1a 86 dd 60 00 00 00 00 10 11 01 fe 80 |......`.........|
00000040 00 00 00 00 00 00 06 ce ef ff fe ca fe 1a ff 02 |................|
00000050 00 00 00 00 00 00 00 00 00 00 00 02 10 01 be 8f |................|
00000060 03 e9 00 10 99 68 6e 6f 64 65 69 6e 66 6f |.....hnodeinfo|
我尝试使用以下代码复制这个行为：
const MultiCastGroup string = "ff02:0:0:0:0:0:2:1001"
const Port int = 1001
const Proto string = "udp6"
const MaxDataGramSize int = 8192
var announcedAddr = &net.UDPAddr{IP: net.ParseIP(MultiCastGroup), Port: Port}
buf := []byte("nodeinfo")
unicastConn, _ := net.ListenUDP(Proto, &net.UDPAddr{IP: net.IPv6zero, Port: 0})
unicastConn.WriteToUDP(buf, announcedAddr)
但我认为它没有起作用，因为我通过tcpdump只能捕获到以下内容：
00000000 d4 c3 b2 a1 02 00 04 00 00 00 00 00 00 00 00 00 |................|
00000010 ff ff 00 00 01 00 00 00 |........|
00000018
似乎连数据包都没有发送出去。我在Debian Wheezy机器上尝试了这个。有人在使用golang和UDP时遇到类似的问题吗？
提前感谢。
英文:
currently I try to reimplement a C application in go. Part of the C application is to send a string to a multicast group. This produces the following packet captured via tcpdump:
00000000 d4 c3 b2 a1 02 00 04 00 00 00 00 00 00 00 00 00 |................|
00000010 ff ff 00 00 01 00 00 00 14 81 06 56 47 2c 01 00 |...........VG,..|
00000020 46 00 00 00 46 00 00 00 33 33 00 02 10 01 04 ce |F...F...33......|
00000030 ef ca fe 1a 86 dd 60 00 00 00 00 10 11 01 fe 80 |......`.........|
00000040 00 00 00 00 00 00 06 ce ef ff fe ca fe 1a ff 02 |................|
00000050 00 00 00 00 00 00 00 00 00 00 00 02 10 01 be 8f |................|
00000060 03 e9 00 10 99 68 6e 6f 64 65 69 6e 66 6f |.....hnodeinfo|
I tried to replicate the behavior with the following code:
const MultiCastGroup string = "ff02:0:0:0:0:0:2:1001"
const Port int = 1001
const Proto string = "udp6"
const MaxDataGramSize int = 8192
var announcedAddr = &net.UDPAddr{IP: net.ParseIP(MultiCastGroup), Port: Port}
buf := []byte("nodeinfo")
unicastConn, _ := net.ListenUDP(Proto, &net.UDPAddr{IP: net.IPv6zero, Port: 0})
unicastConn.WriteToUDP(buf, announcedAddr)
But the I don't think that it is working, because all I can capture from this via tcpdump is:
00000000 d4 c3 b2 a1 02 00 04 00 00 00 00 00 00 00 00 00 |................|
00000010 ff ff 00 00 01 00 00 00 |........|
00000018
It doesn't seem that the packet is even send. I tried this on a Debian Wheezy machine. Did anyone if you encounter a similar problem with golang and UDP?
Thanks in advance
答案1
得分: 3
你是否尝试在另一台主机上进行监听？
Go语言（至少在1.4版本中）在多播上有一个硬编码的禁用回环功能。这意味着你无法看到自己发送的数据包。
你可以通过在套接字的文件描述符上调用setsockopt来覆盖此设置，或者使用golang.org/x/net/ipv6库来实现。
你也可以从这里获取代码（需要查找一下）。
英文:
Did you try to listen for it on another host?
Go (at least in 1.4) had a hard coded disable of loopback on multicast. Which means that, you can't see your own packets.
You can override this by calling setsockopt on the socket FD itself, or:
The golang.org/x/net/ipv6 library can do this for you.
Or you can take the code from Here (have to poke around to find it)
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