Location-dependant IGMP

Could someone please enlighten me?

I spent a third of my work today wondering why

  • a modified QUdpSocket only leads to IGMPv1 membership reports
  • a self-written plain old socket multicast client only leads to IGMPv2 joins, but very seldom leaves

Now being at home, I tried both programs and both reliably send IGMPv3 joins and leaves…