Networking is handled by netplan by default in Ubuntu Server 17.10 and later.

Okay thanks, but if i go to /etc/netplan/01-netcfg.yaml then this folder is empty. Is it okay?

What does this report? ls /etc/netplan

If you meant ls /etc/netplan then it says 50-cloud-init.yaml

What's in it? Please edit your question to add the result of: cat /etc/netplan/50-cloud-init.yaml

Done. Seems like its the correct folder. I guess i can now edit it like in the link you gave me?

Yes, please. Post back if you have any other difficulty.

Did it. Bad news is when i reboot and it starts up then it tries to get network working but after 2 mins it says failed.

Paste the file here and give us the link: paste.ubuntu.com

Im sorry, but which file you mean? If server is starting it says: A start job is running for Wait for Network to be Configured(time). After 2 min it says failed and starts the server without network. I can write though whats inside my /etc/netplan/50-cloud-init.yaml.

paste.ubuntu.com/p/H9cJkY2QJp

Does ip addr showconfirm that your wireless interface is wlp12s0? Not wlp2s0 or some such?

Yes, im sure 100% its wlp12s0.

Are there any clues in the log? dmesg | grep -e net -e wlp Paste, please.

Is this a plain old server or a virtual machine or a container or...what?

imgur.com/a/qPpVduW

Its my old laptop, dell inspiron n5030, its about 6 years old. Im trying to get FTP server going. I need static ip as well. Trying to get wifi going first.

"wlp12s0: associated" means that you are connected! I suspect that the long delay is caused by the settings in netplan related to ethernet and that ethernet is not connected. Can you ping? ping -c3 www.ubuntu.com

You are indeed correct i can ping and im connected. But honestly it amazes me because it didn't work before and i dont think i did change something. I tried to ping yesterday as well and i also checked every day ip addr and it clearly said my wlp12s0 is down also no ip addresses was shown. But now i see ip address. I just dont get it. I am also wondering is my ip static now? Because dhcp4 is set to no.

If ip addr show gives the requested address, x.21, then you are static. dhcp4:no means do NOT get an automatic IP from the router and that we will specify the address we want; i.e. static. It sounds like you are all set.

Yes it does(at least i think so). And yes thats what i meant about dhcp saying no. Thanks a lot for your help! By the way what does the line renderer: networkd ? I deleted it and everything works still fine.

How can i restart/start/stop only networking? I read everywhere sudo /etc/init.d/networking restart. But this doesnt work on newer ubuntu, is there only option sudo netplan apply?

Please don't delete netword from netplan. That tells netplan to use the usual networking process instead of Network Manager. It is always very dangerous to delete something from a system file and then ask questions later. In extreme cases, not probably netplan, you could destroy your installation. Google and Ask Ubuntu are your friends. You might try: sudo ip link set wlp12s0 down followed by: sudo ip link set wlp12s0 up

Yes i agree, definitely shouldnt delete files randomly. I did it only because i added it there, if it was already there i wouldnt touch it. But why usual networking process is better than using Network Manager? I googled Network Manager and it seems to be very good thing. What you mean by usual networking process?

Network Manager requires a desktop environment, Unity, Wayland, Gnome, KDE or some such. It is usually unsuitable for a server as a desktop environment requires a running display which is usually not the case in a server. If your server is connected, as it appears to be, you are all set. There is no need to tweak it until it breaks. Your questions and my answers have now strayed far astray from wifi on server 18.04. If you have more questions search this site and if you don't find the answer, start a new question.

Yes indeed. Thanks for the effort.

And just to make a note (cc @chili555), you can use Network Manager on a server, but it's nontrivial to do, and requires you to know how nmcli works. (By default, Server 18.04 and onwards installs without the GUI use netplan(.io) for the 'networking' platform; replacing that with Network Manager is non-trivial, and from my attempts to do so out of curiosity have all ended with a fairly busted up installation that doesn't work with networking very well)

Noted, @ThomasWard

IMHO, Network Manager on a server is like training wheels. Unless, of course, one loves to tweak it until it breaks, reinstall and repeat. I have done some of that myself over the years but life is short...