# Use the below command in your terminal
# No requirments are needed
(echo >/dev/tcp/{host}/{port}) &>/dev/null && echo "open" || echo "close"

# An example below
(echo >/dev/tcp/10.20.20.21/27017) &>/dev/null && echo "open" || echo "close"

# if open then it will return "open"
# if closed then it will return "close"
# if you can't connect to it then it will freeze, use ctrl+c