Cannot create PoolableConnectionFactory (Communications link failure) - Jmeter - jmeter

Question

I'm trying to test database but it is giving me Cannot create PoolableConnectionFactory (Communications link failure) error.
Response message:java.sql.SQLException: Cannot create PoolableConnectionFactory (Communications link failure)
Jdbc connection configuration:
database url:
jdbc:mysql://codebytenepal.com.np:3306/database_cbn
In order to test whether I'm doing anything wrong or not, I created test db in db4free.net and it worked perfectly.
database url in jdbc connection:
jdbc:mysql://db4free.net:3306/shrestha
This works but the above doesn't. What might be the reason?
Thanks in advance

Answer 1

The host you're trying to reach doesn't have port 3306 open as it evidenced by Nmap report
root#af33db8ee27e:/# nmap codebytenepal.com.np
Starting Nmap 7.60 ( https://nmap.org ) at 2020-10-13 15:53 UTC
Nmap scan report for codebytenepal.com.np (192.3.201.45)
Host is up (0.0016s latency).
Not shown: 965 filtered ports
PORT STATE SERVICE
21/tcp open ftp
22/tcp closed ssh
25/tcp open smtp
26/tcp open rsftp
53/tcp open domain
80/tcp open http
110/tcp open pop3
143/tcp open imap
443/tcp open https
587/tcp open submission
993/tcp open imaps
995/tcp open pop3s
8080/tcp closed http-proxy
8443/tcp closed https-alt
8888/tcp open sun-answerbook
49152/tcp closed unknown
49153/tcp closed unknown
49154/tcp closed unknown
49156/tcp closed unknown
49157/tcp closed unknown
49159/tcp closed unknown
49160/tcp closed unknown
49165/tcp closed unknown
49175/tcp closed unknown
49400/tcp closed compaqdiag
50000/tcp closed ibm-db2
51103/tcp closed unknown
52822/tcp closed unknown
54045/tcp closed unknown
54328/tcp closed unknown
55056/tcp closed unknown
55600/tcp closed unknown
56737/tcp closed unknown
62078/tcp closed iphone-sync
65129/tcp closed unknown
For the other host port 3306 is open:
root#af33db8ee27e:/# nmap -F db4free.net
Starting Nmap 7.60 ( https://nmap.org ) at 2020-10-13 15:58 UTC
Nmap scan report for db4free.net (85.10.205.173)
Host is up (0.016s latency).
Not shown: 96 filtered ports
PORT STATE SERVICE
22/tcp open ssh
80/tcp open http
443/tcp open https
3306/tcp open mysql
Nmap done: 1 IP address (1 host up) scanned in 16.49 seconds
So it's absolutely expected that you cannot establish to the connection to codebytenepal.com.np:3306 as it is not open to the world.
If you absolutely need to test it you need to:
Bind the database server to listen on 192.3.201.45 address
Open port 3306 in your firewall
however be aware that it opens a big security hole in your deployment so revert the changes after you're done with your testing
More information: MySQL Database and JMeter - How to Test Your Connection