I have setup a connection using Qt in the LAN, PC1( will send UDP packets to PC2( with no problem.

But now, PC1 and PC2 are now working under different routers. So now PC1 is at ( and PC2 is at ( I have setup a port forwarding on router1 and pulg router1's WAN port to router2's LAN port.

Then I would like to send UDP from PC1 to PC2, what should I put for the destination address for this UDP packet?

  • Nice to see this question here, thanks for moving it voluntarily ... I tried to post a comment on the other question but didn't get there in time. Check my answer below and see if that helps. – JimLohse Jan 25 '16 at 17:14

If I understand your description correctly — a diagram with Ethernet ports and IP addresses labeled would have helped — Router 1 is downstream (farther from the ultimate WAN/Internet connection of this network) from Router 2. If that's right, then PC1 should be able to reach PC2 at, and you shouldn't even need a static port forwarding rule in Router 1, assuming PC1 always initiates the UDP flows.

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    Hi, I am noob in this area. All I can see now is that from router_2's ( setup menu, I can see router_1 is given an address ( And router_1's ISP seems to be ( Does this match your description? – Nyaruko Jan 25 '16 at 17:04
  • @Nyaruko Agreed you don't need port forwarding, this is a good answer, hope mine helps as well. If you get in trouble you can always reset the router, try things out and see what you learn :) – JimLohse Jan 25 '16 at 17:18

I know this defies logic but it has worked for me, try plugging the cable from Router 2 LAN port to an LAN port on Router 1. I know the way you have set it up makes sense, but you're not really plugging LAN to WAN, you are plugging LAN to LAN

Also when you are daisy-chaining routers, be sure to log into the "downstream" router, by your description? The one that is NOT connected to your Cable or DSL modem.

Once logged in turn off wifi (or pay attention to the settings very carefully) and try turning off DHCP as DHCP is provided by the main router.

I have seen issue where this daisy chaining causes speed restrictions on the end of the line, in my case I had a 75Mbps connection but only got 7mbp on the end of the line.

Try speedof.me or some other speed test site to see what you're getting

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