Hi
Are you using the driver and libraries from ST? Are you sure you're
actually receiving the packets and handing them over to lwip? I'm
guessing this has nothing to do with lwip but you need to enable the
reception of multicast frames in the hardware. In my case (based on some
old drivers for STM32F4) this was off by default
Best regards
Jens
On 2018-01-09 21:11, Maarten Roozendaal wrote:
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
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