I am embarrassed to say this but I restarted the services with the commands below and it has been fixed 
Can't believe this could solve the issue. I think you were right Lars, there was a problem about the configuration of the virtual machine this SAP HANA instance is running in. And after I restarted the services, it has gone somehow.
Commands to restart as below:
/etc/init.d/sapinit stop
Followed by.
/etc/init.d/sapinit start
Give it some time and then run this command to check that the processes are all listening to the ports properly. You should see one for 8000 and 30015.
lsof -i -n -P | grep LISTEN