Simon,
Good call! Indeed, I had
failed to set the NETIF_FLAG_IGMP bit in
the netif's flags. Now that I've done that, the function call to join the
multicast group now returns an error code of zero (i.e. no error).
Moreover, I've uncommented
the netconn_bind call and have now successfully received a multicast packet (from
the proper multicast group address) using netconn_recv().
So I am now past a major hurdle,
thanks to your assistance.
Thank you for your "spot
on" help.
Best Regards,
Dave Squires
-----------------------------------
SQUIRES ENGINEERING, INC.
2604 Lowell Circle
Melbourne, FL 32935-2215
phone: (321) 242-8611
website: http://www.squires-eng.com
-----------------------------------
From: address@hidden
[mailto:address@hidden On Behalf Of address@hidden
Sent: Saturday, July 31, 2010 1:57 AM
To: Mailing list for lwIP users
Subject: Re: [lwip-users] Problem doing UDP multicast receive using
netconn API
Do you have NETIF_FLAG_IGMP set in your netif's flags?
Honestly, I haven't used IGMP so far, but looking at the code of
igmp_joingroup(), which is called by netconn_join_leave_group, ERR_VAL is the
default return value, which means that your netif isn't correctly detected
(either it does not have NETIF_FLAG_IGMP set in its netif->flags or the IP
address is wrong, which can't be the problem from reading your code).
Simon
David K Squires wrote:
Dear Group Members,
I am struggling to try to receive UDP multicast messages
with the Atmel UC3A lwip 1.3.2 port.
I have been successfully sending UDP multicast packets with
lwip for a couple of years using the netconn API. But now I need to receive
them in a different FreeRTOS task.
Here are the
particulars:
Multicast Group Address = 224.0.0.0, destination UDP port = 55555
I've enabled the IGMP code in lwip and everything builds
fine. I have coded up several attempts to set up to receive UDP multicast
packets for the above group and port as follows:
=============================== Code snippet
================================================
(other includes here)
/* lwIP includes. */
#include "lwip/api.h"
#include "lwip/memp.h"
#include "lwip/inet.h"
#include "lwip/ip_addr.h"
#include "lwip/udp.h"
(other includes here)
my_task_function()
{
struct ip_addr
s_mcast_ip_addr; //
MCAST IP Address
struct netconn *conn;
int lwip_status;
err_t err;
/* Multicast Group IP address bytes are
specified in MS to LS order here */
/* The group address is 224.0.0.0 */
IP4_ADDR(&s_mcast_ip_addr,(NetConfig_s.udp_mcast_group_addr.addr
>> 24) & 0xff,
(NetConfig_s.udp_mcast_group_addr.addr
>> 16) & 0xff,
(NetConfig_s.udp_mcast_group_addr.addr >> 8) & 0xff,
(NetConfig_s.udp_mcast_group_addr.addr & 0xff));
// Create a new UDP connection
conn = netconn_new(NETCONN_UDP);
// Note: the above call returns a valid pointer
(non-zero)
// Bind to the multicast group address
224.0.0.0 and UDP port 55555 (is this call needed??)
// lwip_status = netconn_bind(conn,
&s_mcast_ip_addr, NetConfig_s.udp_dest_port);
// Allow packets from ANY remote host on any
port. Is this call needed?????
// I suspect this call is not needed for UDP
// netconn_connect(conn, &s_remote_ip_addr,
0);
//
what do we use for "Any UDP Port?"
err = netconn_join_leave_group
(conn,
// netconn *
&s_mcast_ip_addr,
// Multicast Group Address (32-bits: 224.0.0.0)
&NetConfig_s.ip_addr, //
Local interface IP address = 192.168.1.21
NETCONN_JOIN);
// We want to join this multicast group
=============================================================================================
The code from which this snippet was taken compiles fine
with no errors or warnings.
The problem seems to be in the netconn_join_leave_group
function call. It returns err = -9 (ERR_VAL).
The first parameter, conn, is non-zero, indicating a
reasonable, initialized struct netconn pointer.
The second parameter has been checked and really is
224.0.0.0.
The third parameter is a pointer to struct ip_addr which is
initialized with the IP address of our local Ethernet interface.
As you can see, I've commented out calls to the netconn_bind
and netconn_connect functions; it's not clear whether or not these are
necessary.
Examples of using this function seem to be non-existent,
hence my decision to post a humble cry for help on the lwip forum.
Incidentally, I've patched the Atmel UC3A MACB driver to
allow all broadcast and multicast packets to be passed to lwip. However, I am
not yet to the point where this matters, given the above error scenario.
Any help would be greatly appreciated.
Thanks,
Dave Squires
-----------------------------------
SQUIRES
ENGINEERING, INC.
2604
Lowell Circle
Melbourne,
FL 32935-2215
phone:
(321) 242-8611
website:
http://www.squires-eng.com
-----------------------------------
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