Firwall Is Disable Port Is Open - But Unable To Connect From Outside

TROUBLE SHOOTING.
PROBLEM : All the firewall is disable and port is open, but it is unable to connect from outside.

Scenario: iptables is disable, selinux is disable, fiewall is disable , ufw is disable. All the firewalls are disable and port is open, but still it is unable to connect from outside. nmap and telenet also failed.

Root Cause : Even port is open in the particular application we can set the listen address. By default it is localhost.we need to
change into 0.0.0.0 and restart the service, then from outside users able to connect that particular service.

 For Example : Application name monetdb. Command : sudo monetdb set listenaddr=0.0.0.0 /path~~/dbfarm I faced this problem for monetdb application.