Deny by Default

Deny Incoming Traffic by Default

ufw default deny incoming

Deny Outgoing Traffic by Default

ufw default deny outgoing

Allow Incoming Traffic on Specific Port to All Interfaces from All Addresses

ufw allow in 25515

Allow Incoming Traffic on Specific Port to All Interfaces from LAN

ufw allow in from 192.168.1.0/24 to any port 25515

Allow Incoming Traffic on Specific Port to All Interfaces from Specific IP Address

ufw allow in from 192.168.1.2 to any port 25515

Allow Incoming Traffic on Specific Port to Specific interface from Specific IP Address

$ ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    [...]
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    [...]

$ ufw allow in from 192.168.1.2 to eth0 port 25515