linux-cookbook/src/firewall.md

Setting up a firewall

KDE Connect

KDE Connect uses dynamic ports in the range 1714-1764 for UDP and TCP. So, we need to make sure that these ports are open for both TCP and UDP.

ufw

If your firewall is ufw, you can open the necessary ports with:

sudo ufw allow 1714:1764/udp
sudo ufw allow 1714:1764/tcp
sudo ufw reload

firewalld

If your firewall is firewalld, you can open the necessary ports with:

sudo firewall-cmd --permanent --zone=public --add-service=kdeconnect
sudo firewall-cmd --reload

iptables

If your firewall is iptables, you can open the necessary ports with:

sudo iptables -I INPUT -i <yourinterface> -p udp --dport 1714:1764 -m state --state NEW,ESTABLISHED -j ACCEPT
sudo iptables -I INPUT -i <yourinterface> -p tcp --dport 1714:1764 -m state --state NEW,ESTABLISHED -j ACCEPT

sudo iptables -A OUTPUT -o <yourinterface> -p udp --sport 1714:1764 -m state --state NEW,ESTABLISHED -j ACCEPT
sudo iptables -A OUTPUT -o <yourinterface> -p tcp --sport 1714:1764 -m state --state NEW,ESTABLISHED -j ACCEPT

Credits: KDE UserBase Wiki