[Udpcast] Udpcast + firewall

Alain Knaff alain at knaff.lu
Fri Sep 15 13:47:21 CEST 2006

Maciej Nadolski wrote:
> Hash: SHA1
> Hi,
> I'm aware of using udpcast threw firewall, certainly isn't a best
> practice, but I'm sending images from firewalled server, to pcs in
> computer laboratory.
> Server is ofcourse firewalled. I opened ports 9000 and 9001 in firewall
>  for inbound udp connections. All outbound connections are allowed. I'm
> using OpenSuse 10.1, but it shouldn't be the case.
> udp-receiver or udp-sender on server, always have to be executed at the
> end. If it isn't done like that, the sender and receiver doesen't find
> themselves threw broadcast.
> Firewall is blocking something for sure, but I have no idea, what. Could
> you tell me what rule in fw I missed?
> Thanks.

Port 9000 and 9001 in both directions should be enough.

Try to set up your firewall to log all rejected packets (-j LOG target), 
and check what is blocked.

Also, make sure that it is indeed a firewalling issue (i.e. does it work 
with firewall off?), and not something else, like a mismatched broadcast 
address or subnet mask on senders and receivers.



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