[lwip-users] netconn receive UDP via multicast address

[Maarten Roozendaal]

Goodday,

 

I am working on an implementation of lwip netconn api in combination with FreeRTOS. I use lwip version 2.0.0 on an STM32F7 microcontroller with FreeRTOS V9.0.0

I want to use lwip to receive UDP packets from a mullticast adress. 239.0.0.0 in this case.

 

The system running lwip is assigned a static ip adress, being 192.169.123.109.

 

When sending UDP packets to 192.169.123.109 directly I can process them and echo them back. However, I need to be able to read UDP packets send to the multicast ip adress 239.0.0.0. To accomplish this I use the following task:

 

static void vUDPnetconnTask(void *pvParameters)

{

  static struct netconn *conn;

  static struct netbuf *buf;

  ip_addr_t DestIPaddr, OwnAddr;

  err_t err, recv_err;

 

  LWIP_UNUSED_ARG(pvParameters);

 

  netif_default->flags = NETIF_FLAG_UP | NETIF_FLAG_BROADCAST | NETIF_FLAG_ETHARP | NETIF_FLAG_LINK_UP | NETIF_FLAG_IGMP;

  

  IP4_ADDR(&MulticastIPaddr, 239, 0, 0, 0);

  IP4_ADDR(&OwnAddr, 192, 168, 123, 109);

   

  conn = netconn_new(NETCONN_UDP);

  if (conn!= NULL)

  {

    netconn_bind(conn, IP_ADDR_ANY, 60004);  // returns ERR_OK

    err = netconn_join_leave_group(conn, &MulticastIPaddr, &OwnAddr, NETCONN_JOIN); // returns ERR_OK

    if (err == ERR_OK)

    {

      while (1)

      {

        recv_err = netconn_recv(conn, &buf);

      

        if (recv_err == ERR_OK)

        {

            // process the packet

        }

      }

    }

    else

    {

      netconn_delete(conn);

    }

  }

 

}

 

So, I bind to IP_ADDR_ANY using port 60004 (this is the port that the multicast address receives UDP packets on) and I use the function netconn_join_leave_group() to subribe to the multicast address.

 

I do not get any error returns but I do not receive any UDP packets send to 293.0.0.0.

 

I have been trying for a long time to get this to work but feel like I am missing something fundamental. Is there a way to accomplish what I need?

 

Help is very much appriciated!

 

Greetings,

 

Maarten