[lwip-users] LWIP + IGMP

Dear all,

I want to receive UDP-packets from a multicast message. The system currently can receive unicast messages.

To receive multicast messages I’ve set the following settings in lwipopts.h

#define LWIP_IGMP 1

#define MEMP_NUM_IGMP_GROUP 8

Also in the initialize function I’ve set the right flag

netif->flags = NETIF_FLAG_BROADCAST | NETIF_FLAG_ETHARP | NETIF_FLAG_UP | NETIF_FLAG_IGMP | NETIF_FLAG_ETHERNET;

The initializing of the IGMP-group is as follows

uint16 port;

ip_addr_t groupAddress;

getParamatersFromTransmissionGroup (group, &port, &groupAddress);

__udpSocket = udp_new ();

MF_ASSERT (__udpSocket != NULL);

err_t err = udp_bind (__udpSocket, IP_ADDR_ANY, port);

MF_ASSERT (err == ERR_OK);

err = igmp_joingroup (&localAddr, &groupAddress);

MF_ASSERT (err == ERR_OK);

udp_recv (__udpSocket, data_received, this);

When I send data directly to the IP address assigned in LWIP I get to the breakpoint in data_received.

However when I change the destination IP address to the one configured in groupAddress, I get no data at all.

I’ve made some tests in Wireshark where I captured the packets. The test system consists of three devices

192.168.172.1 > Router

192.168.172.20 > Computer with Wireshark

192.168.172.113 > LWIP Device

I’ve attached the capturefile done in Wireshark, In this file you can see the LWIP device responds to a query.

If you need any more information, please reply to this mail.

Met vriendelijke groet, Best regards,

Ricardo Schoof | R&D Engineer