we are using the WIZ550 io module containing the Wiznet W5500 chip in a
multicast environment. Direct receive and send functionality works
fine, but when opening a multicast socket, only a ‘Report Group’ IGMP
message but no ‘Join Group’ message is transmitted.
According to the description at
a ‘Join Group’ message should be sent automatically when opening the
socket. Unfortunately, the switches require the ‘Join Group’ message as
a ‘Report Group’ message does not register the device as recipient.
Is there any point we are missing which causes this behavior? Or does
the W5500 generally not transmit ‘Join Group’ messages.