Apps like Knock on Ports

Here are some great alternatives to Knock on Ports by Alexander Yaburov :
UDP Guard
UDP Guard
★4.4
Ping: test high latency, delay
Ping: test high latency, delay
★4.1
TCP Ports list
TCP Ports list
★4.6
UDP TCP Server
UDP TCP Server
★3.9
UDP Sender / Receiver
UDP Sender / Receiver
★3.2
NoobzVpn
NoobzVpn
★4.7
Port Authority - Port Scanner
Port Authority - Port Scanner
★4.1
UDP Terminal
UDP Terminal
★3.9
ALFAISAL Inject
ALFAISAL Inject
★3.9
TCP UDP Server & Client
TCP UDP Server & Client
★4.5
Packet Injection
Packet Injection
★3.8
Knock In VIP Messenger
Knock In VIP Messenger
★3.4
Fast Port Scanner
Fast Port Scanner
★3.5
UDP/TCP Widget
UDP/TCP Widget
★4.9
STU for NAT
STU for NAT
★3.5
Advanced PortChecker
Advanced PortChecker
★4.3