I am trying to write a simpler client server program, using my laptop as the server and several Android devices as clients. The server listens on a port (say, 5902) until a client tries to connect. Threads are spawned on the server, and communications happen.
In a friendly lab environment with basically no firewall, this works fine.
At home, I have AT&T U-Verse with their Motorola NVG510 router and its default firewall. My crude understanding is that I need to open that port on the firewall for each device because that is now the NVG510 opens ports-- on a per device basis.
But, trying to open the same port on multiple devices gives me a pinhole conflict error (which I assume is exactly what it sounds like-- opening the port is a pinhole, and having the same port opened for two devices is the conflict.)
Is there any way to do what I am trying to do on my home router? It would be nice to work on this project at home.
(Note: This is strictly about the networking issue. The core client/server software works in other environments.)
Update: In the benign lab environment, each device has its own IP address. In my home network, I'm limited to the port-forwarded addresses 192.168.1.x, which I suspect is the key difference.
2 Answers
You forward traffic coming in on a port to a device behind the firewall. No need to open a port "for each device" if they are all hitting the same service.
Imagine it was a public-facing service, would you expect to have to open a port for each and every person on the Internet who might want to access it? :)
Anyhow, for your NVG510: under NAT/Gaming you create a 'Custom Service' (Name, port to listen on, protocols to forward), then add a 'Hosted Application' for which you choose your new custom service you just made, and enter the IP of the server you want to forward that traffic to.
Most clients like SSH have the option to put a different port so for example your server is 5902 you put the client to go to 5903 on the router forward port 5903 to 5902 means you can have more than one device forwarded to the same port
