Testing UDP and TCP Port Connections in Debian Linux  
Install the tool nc:
sudo apt-get install nc
To verify if a TCP connection on host 192.168.10.12 port 123 is possible:
nc -z -v 192.168.10.12 123
To verify if a UDP connection on host 192.168.10.12 port 123 is possible:
nc -z -v -u 192.168.10.12 123
If the connection is possible, nc will output:
Connection to 192.168.10.12 123 port [udp/ntp] succeeded!
10.15.20
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