RTCS doesn't receive broadcast datagrams on subnet, bug?

[TomR]

I am trying to send UDP frames to an MQX system using broadcast messages.

The MQX system has a DHCP assigned IP address of 192.168.0.5 and a netmask of 255.255.255.0.

• UDP frames sent to 192.168.0.5 are rx ok
• UDP frames sent to 255.255.255.255 are rx ok
• UDP frames sent to 192.168.0.255 are not rx

Sniffing the wire, both the 255.255.255.255 and 192.168.0.255 frames are sent with a destination MAC address of ff:ff:ff:ff:ff:ff as expected.

RTCS IP statistics show the UDP frames sent to 192.168.0.255 are being discarded.

This seems broken. I have a different platform (non-MQX) where is works.

Is there a setting that I'm overlooking?

My code looks like this:

 struct sockaddr_in any;

 udp_ethernet = socket(PF_INET, SOCK_DGRAM, 0);

 any.sin_family      = AF_INET;

 any.sin_port        = MY_PORT;

 any.sin_addr.s_addr = INADDR_ANY;

 bind(udp_ethernet, &any, sizeof(any));

 rlen = sizeof(raddr);

 memset(&raddr, 0, rlen);

 len = recvfrom(udp_ethernet, data, DATA_LEN, 0, &raddr, &rlen);

Thanks

Tom 

[DiegoSpinola]

@TomR

 I'm having the exact same issue , have you been able to solve it ?

[DiegoSpinola · Accepted solution]

Solved!

Recompile your Libs with the RTCSCFG_IP_DISABLE_DIRECTED_BROADCAST defined to 0 at user_config.h

#define RTCSCFG_IP_DISABLE_DIRECTED_BROADCAST 0

[dank60]

I tried to do this and it works if I build my libs in debug configuration. If I build them in release configuration I can't receive broadcast frames... I don't know what I have to do...

[dank60]

I tried building rtcs library  with different compiler's optimization levels : with level 1 no problem, with level 2 or superior broadcast udp reception doesn't work.

[TomR]

Additional debugging info:

The datagram sent to 192.168.0.255 is being dropped in the function IP_route_local(). It discards the packet and increments the rx discarded count and the rx addr errors count.

[boogy]

You have gotten farther than me. I can't recieve a broadcast (255,255,255,255) datagram.

I am currently using a stream socket and wanted to add a datagram socket to recieve broadcast datagrams.

What settings allow the reception of UDP broadcasts ?

[TomR]

The code fragment above will do the trick. Nothing more is needed on the receive side.

Typically the problem to send a broadcast datagram is on the sending end. Make sure that you've done a setsockopt(SO_BROADCAST) on the sending socket.

Have you sniffed the wire and observed that the packet is being sent on the wire?