Question: After installing and starting VNC server on *Compute Engine*'s **Ubuntu16 instance** VNC session cannot be made. I would like to open **Network**'s Firewall ports to see if it would make a difference.
How to configure Firewall rule?

[![enter image description here](https://i.stack.imgur.com/4TW9m.png)](https://i.stack.imgur.com/4TW9m.png)

Answer: 
first create your firewall rule for tcp or udp, then set tag in firewall rule. 
after creating firewall rule note down tag, go to VM instances click on edit add tag name that you created in firewall rule. it will open that port. 
[![enter image description here](https://i.stack.imgur.com/xa6Fo.png)](https://i.stack.imgur.com/xa6Fo.png)
[!VM Edit for tag[1](https://i.stack.imgur.com/v1qVV.jpg)](https://i.stack.imgur.com/v1qVV.jpg)

This screenshot to edit VM instances and add your tag that you created in firewall rule.