unable to broadcast more than 1472 bytes of data in a udp br

QNX Newsgroups (Archives) qdn.public.qnxrtp.os
1

I have set the sendbuffer size to 8192 using setsockopt and verified that it
is set to 8192 using the getsockopt function. However I can only send a
maximum of 1472 bytes of data. If I try to send 1473 or more I get an error
of “Message too long”.

Anyone have any thoughts?

2

Hi Freddy,

I believe the maximum message size for a UDP broadcast is limited by the MTU
size of the underlying link, which in the case of ethernet is 1500 bytes.

Regards,
Barry F.

freddy <lmccambley@excalibur.com> wrote in message
news:b2e1ff$jfh$1@inn.qnx.com…

I have set the sendbuffer size to 8192 using setsockopt and verified that
it
is set to 8192 using the getsockopt function. However I can only send a
maximum of 1472 bytes of data. If I try to send 1473 or more I get an
error
of “Message too long”.

Anyone have any thoughts?

3

Your packet (plus headers) winds up being > the mtu of the link.
Broadcast packets are prohibited from being fragmented.

-seanb

freddy <lmccambley@excalibur.com> wrote:

I have set the sendbuffer size to 8192 using setsockopt and verified that it
is set to 8192 using the getsockopt function. However I can only send a
maximum of 1472 bytes of data. If I try to send 1473 or more I get an error
of “Message too long”.

Anyone have any thoughts?

4

thank you…

Freddy.

“OS Support” <os@qnx.com> wrote in message news:b2e6al$7j7$1@nntp.qnx.com…

Hi Freddy,

I believe the maximum message size for a UDP broadcast is limited by the
MTU
size of the underlying link, which in the case of ethernet is 1500 bytes.

Regards,
Barry F.

freddy <> lmccambley@excalibur.com> > wrote in message
news:b2e1ff$jfh$> 1@inn.qnx.com> …
I have set the sendbuffer size to 8192 using setsockopt and verified
that
it
is set to 8192 using the getsockopt function. However I can only send a
maximum of 1472 bytes of data. If I try to send 1473 or more I get an
error
of “Message too long”.

Anyone have any thoughts?
\

5

thanks.

Freddy.


“Sean Boudreau” <seanb@node25.ott.qnx.com> wrote in message
news:b2e6fs$7hv$1@nntp.qnx.com…

Your packet (plus headers) winds up being > the mtu of the link.
Broadcast packets are prohibited from being fragmented.

-seanb

freddy <> lmccambley@excalibur.com> > wrote:
I have set the sendbuffer size to 8192 using setsockopt and verified
that it
is set to 8192 using the getsockopt function. However I can only send a
maximum of 1472 bytes of data. If I try to send 1473 or more I get an
error
of “Message too long”.

Anyone have any thoughts?