Problems with dropping current connection and blocking access to WAN

RouterOS Beginner Basics
1

I currently have a webcam that communicates over port 42157. With my previous firewall I blocked access to that webcam port when I did not want to broadcast video over WAN.
If I did want to view the video over WAN or Internet, I would open that port up.

I am having problems with doing this on my Mikrotik. For simplicity, we can block all ports.

I have a cellphone app that from the Internet can connect to my LAN and view live video.
I can create a firewall rule for my webcam IP 192.168.1.10 and prevent my client cellphone app from connecting to my LAN. The problem is, my firewall rule will not drop any current connection that is already made to my webcam. If I press the disconnect option on my cellphone app, I will not be able to reconnect to the webcam. How can I use a firewall rule to drop the current connection without having to press the disconnect option on my cellphone?

I am using the GUI but my firewall rule will be something such as:
/ip firewall filter add action=drop chain=forward src-address=192.168.1.10

I want to enable that rule and immediately drop any webcam connections. This way if anyone is currently connected to the webcam, they will immediately lose their connection.

2

You can either remove all current connections to the cam manually (IP → Firewall → Connections).
Or you can move you rule higher then established/related one, but that can result an additional CPU load (because all traffic will be checked by this rule, even the connections that were already established).

3

IP → Firewall → Connections works perfect for me. Thanks.