Re: [lwip-users] Once UDP fails to receive then resending fails as well

[Patrick Klos]

On 5/5/2017 12:37 PM, digitalwave wrote:
> 1 MCU hooked up with a router as I took over this project but it didn't let
> me trace down with Wireshark. I asked him and he replaced it with a switch
> (Dell connect 6224). I am not a network guy so I thought he set up and gave
> me a right thing.
>
> 2. Before this issue happended the assigend IP using DHCP was 192.x.x.x ,and
> he changed to 172.x.x.x. I think he also changed sub-net mask for doing
> this. I had a problem to obtain IP with the changed network environment, and
> I told him and now MCU can receive IP without any issues.

What are the network details?  Make sure they configured the same on the 
HP-Unix machine as well?

> 3. There are so many transactions going on between MCU and the server. Most
> traffic takes place not very often, but the issue came out form a
> transaction that checks the server time every 1~2 seconds depending on how
> MCU schedules up. Now it set up every 1 second. I looked at the HP-UNIX and
> one fo the parameter deals with TCP idle something set up 7200 seconds, but
> MCU transacts every 1 second so it is not the matter of that I believe.

OK, so it sounds like even if the HP-Unix system has some kind of 
firewall rules, they shouldn't be timing out.

> The network guy barely open things up as what he has chnaged, so it is hard
> for me to know what has changed and what will be affected due to that.

Let's go back to the idea of running tcpdump on the HP-Unix machine.  
You might even get rid of the switch between the HP-Unix and the Tiva 
and make it a direct connection? (simplify the network as much as 
possible, at least until you find the problem)

Another possibility (if your "network guy" is up to it?) is to configure 
the Dell 6224 Switch to monitor the ports being used between the Tiva 
and the HP-Unix machine, and feed the monitored traffic to a port that 
goes to your Wireshark machine?  Those things can be tricky (i.e. a pain 
in the ass), so you really need to know what's going on.

> I thank you to give ideas.

It's my pleasure.

Good luck!

Patrick Klos
Klos Technologies, Inc.