Open ports on Chromebook 4+

[Jim Lohse]

Hi,

I just got this Chromebook 4+ but I've seen it on other Chromebooks, hence I'm posting here. Trying to run the DJITelloLib package, it can connect to a drone and issue a command on port 8889 but appears to fail listening for a response on port 8890.

I assume I can originate a connection on a port, but not listen on a port for incoming connections? If this was pure Linux I'd have a clue.

I don't know how Chromeos manages its firewall, I haven't figured out how to configure it.

Any suggestions how I can open port 8890 on the Chromebook? (assuming I've correctly diagnosed the issue)

Thanks for any help

[Keith I Myers]

In the Linux Settings, there is a option for port forwarding. Have you tried that? 

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[Jim Lohse]

I should have mentioned, I did do that already.

I thought maybe that only opens the port to ChromeOS and somehow ChromeOS is still blocking port 8890 from the rest of the network?

I've googled a lot and everything I've found for ports and firewalls talks about that port forwarding, but I'm trying to understand how the firewall in ChromeOS works, can it be configured?

[Jim Lohse]

I've done some more investigation, it seems like the port forwarding is working. I wrote a little chat server and client to test it out, it works, with a caveat. Here's what's happening:

The Linux container that lives inside ChromeOS can't advertise its own ports to the world, apparently. Thus the need for port forwarding, which works.

Add into this the fact that the Linux container lives in its own subnet, and while ChromeOS has a route to the container internally, it doesn't appear to route outside traffic to this internal subnet. Security, I guess?

So bottom line, the client on another computer needs to talk to the IP of the Chromebook, not the IP of the container where Python is running the drone program.

[Jim Lohse]

I thought I entered more info hours ago, I think I've discovered the problem. When the library I'm using sets up a socket, it binds to the IP address of the Chromebook container.

The drone gets that internal Linux container IP to respond to, which is not in the same network as the ChromeOS IP address your router handed out.

Then when the drone replies to that internal IP address, there's no external route, so it fails.

So I consider this solved, I don't expect anyone to fix this library for me :) Thanks.

On Tuesday, April 5, 2022 at 5:59:34 PM UTC-6 Jim Lohse wrote: