Run command " systemctl status hsqld.service " to check the database status.

The below picture shows when the database service is not running 

Use the lsof -i command to see the list of opened files
run lsof -i:9001

The command will list all running process IDs on port 9001  as shown below

Run the command $ kill <PID> (replace with the top PUD running e.g kill 1137.

Start HSQDB service     (systemctl start hsqldb.service)

Restart esp service  (systemctl restart esp.service)

Restart espconfigagent  (systemctl restart espconfigagent.service)

run eSocket test App in terminal ?