Server application is C++ using winsock 1.1īoth on a working setup and on the faulty setup I see a IGMP packet from 172.21.100.1 (server) to 224.0.0.22 with type = 0x22 and m_address = 230.21.1.200īoth on a working setup and on the faulty setup I see the server sending multiple UDP packets as multicast from 172.21.100.1 (server) to 230.21.1.200 (src and dst port equal 14800) at regular intervals. Using WinXP Professional tried with both sp2 and sp3 - no difference. The concise info on this is here (and yes it does apply to Windows XP as per There is at least one registry setting IGMPLevel that is incorrectly set, will mean the IP stack will not receive multicast. (I'm not sure if this is actually possible not knowing a lot of details about your code or the stackĢ. You are binding both as a listener and sender and it is possible that may mean (at least in the broken case) that your listener is not ready when you are sending.
Is there possibly a timing issue in the broken machine. There are two things I can think of hereġ. So if you do receive packets (on the working) machine that you send, it must be within the local stack. (Basically because of the learned source MAC address). I fairly certain that a switch will not hairpin multicast traffic back to a sender.
It was not enough to just turn off the damn thing, by uninstalling the software package the problem was fixed. The problem turns out to be the firewall after all.
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