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