I set up a simple webserver on a LAN PC connected to internet via an Android hotspot.
Previously, I did the same via a local wired router and worked out fine with simple NATting and an automatic dynamic IP checking.
I’d like to do the same again but via Android as a router, just I do not know how.
Any idea and hints?
Thank you
Hi @alimurgia,
For that you’ll have to setup port forwarding on both the router as well as the Android hotspot. I don’t know if it can be done or how to do it with/on the hotspot, so don’t know the pratice, only the theory.
Hope this helps! Although I doubt it
Well, I no longer use a “traditional” router, just tethering via Android hotspot.
Point #1 is: NATting via Android…
Any practical hint?
Nah, sorry.
But have a look here:
https://stackoverflow.com/questions/10367727/android-nat-traversal
read but it does makes no sense to me 
I am looking for a simpler solution such maybe a couple of commands in adb… dunno…
Me neither.
I can tell you that you’ll get more help, and theoretically easier help, elsewhere, like S.O. or similar, than on the Manjaro forums though.
My first thought is - you cannot - due to how Android handles network.
While you can create outgoing traffic - but you cannot get incoming traffic routed to the tethered device.
Maybe you can find a way around it … an app perhaps, but I wouldn’t get my hopes up.
EDIT:
Got curious - perhaps you can get ideas from this search
I’ve also found it right now:
https://android.stackexchange.com/questions/168422/how-to-port-forward-internet-using-android-hotspot-to-pc
Looks nice… going to give a try and refer back…
5 mins later:
I would then stick to nc.
Does anyone knows the correct syntax?
In gnu-netcat, there is no -k option.
In openbsd-netcat, there is.
You apparently have gnu-netcat, so the command copy/paste will not work there.
no,no!
I attempted installing vanilla netcat but termux refused yelling the only available source was netcat-openbsd.
Seemingly, this netcat complains something about the -e option…
BTW:
-installed version is confirmed to be netcad-openbsd 1.21.7-2-3
-even without -k option does not want to work
WHAT WORKS:
nc -p 8000 192.168.40.20 8000 seems at least to be accepted (not sure working…)
you did not mention this initially 
from the man page of openbsd-netcat:
There is no -c or -e option in this netcat, but you still can execute a command after connection being established by redirecting file descriptors. Be cau‐
tious here because opening a port and let anyone connected execute arbitrary command on your site is DANGEROUS. If you really need to do this, here is an ex‐
ample:
I don’t know what the person writing the post was using - or whether they simply wrote from memory without testing.
Up to now:
1-catching up android external IP is done via:
echo $(wget -qO - https://api.ipify.org)
I get the IP W.X.Y.Z
2-then this nc SEEMS to work (at least accepted):
nc -p 8000 192.168.43.20 8000
3-then I take another android phone, in a browser I key in W.X.Y.Z:8000 but the browser:
I think nc is not yet totally right
Anyone has better commands as a safer alternative?
I think you need to understand what they mean when they call it dangerous.
In your scenario, it probably isn’t. (cave: dangerous half knowledge …)
… and an example is in that very man page, right below the excerpt I posted
I don’t know much about this - I’m here watching and learning.
I just felt prompted to respond re your syntax error issue …
Keep in mind that a lot of mobile ISPs are using CG-NAT and then no amount of port forwarding or whatever on your android will help.
Some providers allow you to change the APN so that the phone gets a public address.
I have done that in the past.
OK, so what piece of info do I have to input in the APN conf to get a public IP?
so if a digital nomad is trying to set up an "home"server (not having an home by definition) he is prevented. So no “home"servermusicstreamer - no"home”-own-chat-serverx etc.
One can only make use of a “homed” router in a fixed location!?
Search for it or call your provider…
I guess you’d first need to find out whether your provider is one of them?
… or if you actually will have a problem with CG-NAT
I think you are jumping to conclusions too quickly.