Problem:  kubectl get nodes shows an error The connection to the server IP:6443 was refused - did you specify the right host or port?

Solution: Make sure you disable memory swapping if you are on Linux Ubuntu18.04 like so:  

swapoff -a 

- If you are using a firewall on your server make sure you allow port 6443 both UDP and TCP for Kubernates to work. 

ufw allow 6443/udp && ufw allow 6443/tcp

- Try again by kubectl get nodes if you have any nodes will appear if not, the outcome will be

NAME          STATUS     ROLES    AGE   VERSION

master-node   NotReady   <none>   13s   v1.17.0