Is there a manual for configuring D-Link Wireless N 150 ADSL2+ Modem Router DSL-2640U via CLI Telnet?

Question

Command line

Hello. There is a router (192.168.1.1) distributing Wi-Fi and one PC (192.168.1.7) connected by a twisted pair cable. The goal is to open port 27015 on the router so that it can pass to the PC. Configured through the browser GUI, the port is open. But the Router is not clear for what reason it can reset the Internet connection, which is restored, but the port remains closed until I reboot the router by turning off the power. I read that the browser setting is unreliable and sometimes does not work correctly. I read about configuring routers via a console cable, but then I discovered the lack of a console port on the router. Then from Windows via cmd.exe launched Telnet and connected to the router via local network (open 192.168.1.1). The welcome message says BusyBox v1.19.2 and prompts you to enter the 'help' command to see a list of built-in commands. Command List:
.
:
break
cd
chdir
continue
eval
exec
exit
export
false
getopts
hash
help
let
local
pwd
read
readonly
return
set
shift
times
trap
true
type
ulimit
umask
unset
wait The
trouble is, I have no idea where to get the description of these commands. Commands like "help set" simply print the same list of commands. Does anyone know where you can read something about them, find out, etc. Where are the port settings, ip and everything else stored?
I will be grateful for any help. If I wrote something wrong, please do not judge strictly, I am a novice in this matter.

Answer 1

Got a response from support. You need to dial resident_cli from telnet and start dancing from there. There, help can also be written to display commands that can change parameters, and the commands are more or less understandable. And about a normal router - I bought dlink before I started to be interested in routing, etc. I had no idea that router norms should have a console port. Thanks to all.

Answer 2

Browser setting and setting through which thread is different are absolutely equivalent.
the help command gives you a list of busybox commands, the command shell in your modem. It has nothing to do with the firewall settings. The firewall is configured using the iptables command. Where its settings are stored - you need to understand the firmware of your modem.

Answer 3

Telnet is read-only. You can see top, etc.

Answer 4

Buy yourself a decent router. Gnilink ignored all bug reports on this router... Gnilink is now busy drawing another fundamentally new graphical interface.
PS
If there is no way out at all, try updating the firmware to version 2.0.5, it is more or less stable.