This set ends with the most useful task on the site: you start a real server on your own device and scan it, then read the result. Nothing here touches anyone else's network.
Each one is marked as you go, and the explanation arrives straight after, which is
the part worth reading.
4 questions, marked as you go.
Tasks
These need your own device. Run the command in Termux, then paste what it printed.
The marking looks at what the output means, so spacing, version numbers and
ordering do not matter. If you have not installed anything yet, the
lesson covers the setup.
Start a server and scan it
This starts a small web server on port 8022, scans that port on your own device, then stops the server again. Paste the scan output, not the whole terminal session.
Run this in Termux
On your own device. Nothing on this page executes it. The command runs in
your terminal, and this box only reads what you paste back.
netstat -tln lists what is listening on your device right now, so you can check the server came up before you scan it.
the output is from nmap
it has a port table with PORT, STATE and SERVICE columns
a port is reported as open
the commands actually ran
What a good answer looks like
You should see nmap's usual shape: a banner line naming the version, a scan report naming the host, a blank line, then a table with the columns PORT, STATE and SERVICE, and one row for the port you scanned. The row should read 8022/tcp, then open, then the service it identified. Then a note that service detection was performed, and a summary line at the end. The parts worth reading are the STATE column, which is the answer to your question, and the SERVICE and VERSION columns, which tell you what is actually answering and how old it is. Every open port on a device you own is something to keep patched. The same exercise works on the SSH server Termux ships: start it with sshd and it listens on the same port.
Marking your own work
Both halves of this are checked in your browser, with no server involved, so nothing
stops you from pasting output you did not run. The tasks are written so that the
easiest way to pass one is to actually do it and read the result, which is the whole
intention.