UDP Multicast - IGMP packet format

I am working with the standard Ethernet library (Wiznet chip) to create a UDP multicast receiver.

When the thing connects it needs to send an IGMP packet to connect to the appropriate multicast socket. This causes the packets to be routed correctly.

I see a call for sending this packet in socket.h but have not found the code to construct the packet that needs to be sent.

uint16_t igmpsend(SOCKET s, const uint8_t * buf, uint16_t len) ()

Clearly I could go to the RFC and write the code from scratch but would hate to re-invent the wheel. Has anyone done this?

Thx Paul

have you checked the old forum?

I recall it is mentioned several times, e.g. - http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1284323807 - (multicast enable bit)

You might need to search for UPnP too as it seems to use related code patterns.