IP_MULTICAST_TTL and windows7

Asked Nov 27 '12 at 17:54

Active Nov 28 '12 at 01:01

Viewed 1,923 times

My application is creating an UDP socket and setting some options. One of the option is IP_MULTICAST_TTL.

When the application is running on windows 7, and I observe the traffic on the wire with wireshark, I can see that the TTL is always 1, meaning that the setsockopt() is not having any effect (it does not return an error though).

Digging into the code I found that IP_MULTICAST_TTL value is 10 on Windows 7, 3 on other Windows versions.

If I force the value to be 3 on Windows 7, setsockopt() works just fine and wireshark is reporting the right value.

I found this article: http://support.microsoft.com/kb/257460 and I verify that I'm including Ws2tcpip.h after Winsock2.h and that i am linking against Ws2_32.lib

Any suggestions?

edited Nov 28 '12 at 01:01

user207421

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asked Nov 27 '12 at 17:54

magopieri

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And you want larger TTL on multicast packets for ...? – Nikolai Fetissov Nov 27 '12 at 18:30
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The same compiler on each platform? – Steve-o Nov 27 '12 at 19:04
@NikolaiNFetissov : The larger TTL is needed to cross a "long-distance" network – magopieri Nov 27 '12 at 19:13
@Steve-o: yes, same compiler on each platform. – magopieri Nov 27 '12 at 19:13
And the "long-distance" network is configured to forward multicast, right? – Nikolai Fetissov Nov 27 '12 at 19:31
yes, @NikolaiNFetissov. But, beside the actually usage, I just want to set IP_MULTICAST_TTL but windows7 does not allow me because the constant is defined wrong.. – magopieri Nov 27 '12 at 22:18
I suggest that you aren't doing what you think you're doing. The recommendations in the KB article are quite clear. You could try doing the first option: use Winsock2.h and Wsock2.lib only. – user207421 Nov 28 '12 at 01:04

IP_MULTICAST_TTL and windows7

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