weird error while creating mysql connection in jdbc

Question

Note: I have Googled a LOT and found hundreds of suggestions for this problem but nothing seem to work for me. That's why I am posting a duplicate looking question

I am getting a weird error in my java program

org.apache.tomcat.dbcp.dbcp.SQLNestedException:
Cannot create PoolableConnectionFactory (Communications link failure,
The last packet sent successfully to the server was 0 milliseconds ago.
The driver has not received any packets from the server.)

I am not able to figure out what's wrong. I tried updating mysql jar file, closing other mysql connections, increasing connection limit, restart mysql/tomcat, etc..

Surprisingly, the connection properly works in a different project of mine using exactly same db configs.

This problem started suddenly, I haven't changed a bit in db config lately.

Any info on possible causes will help me debug this issue further.

Did you check your network settings? Sometimes firewall may be blocking the connection — Thusitha Thilina Dayaratne, Aug 27 '14 at 06:46
Yes, but I am thinking, if firewall is the issue, how it suddenly started blocking without any change. — Salman, Aug 27 '14 at 06:47
Issue is not predictable. If you are running the app from an IDE, close and restart it. It may get resolved. — Ravinder Reddy, Aug 27 '14 at 06:48
Are you working on your own machine or a network machine? i mean in a office environment?\ — Thusitha Thilina Dayaratne, Aug 27 '14 at 06:49
@Салман:- Does this help:- http://stackoverflow.com/questions/2121829/mysql-jdbc-communications-link-failure — Rahul Tripathi, Aug 27 '14 at 06:50
Yes, I tried restarting IDE. @ThusithaThilinaDayaratne Office env. One thing I think I should mention is, few days back it happened with two of my friends PC and we couldn't figure out what's wrong. and now it started in mine — Salman, Aug 27 '14 at 06:51
@R.T. The link you gave is in fact a linked post. I tried that as well. — Salman, Aug 27 '14 at 06:52
may be they have integrate some new rules or change some configurations in the firewall. — Thusitha Thilina Dayaratne, Aug 27 '14 at 06:53
@ThusithaThilinaDayaratne I agree that could be a possibility, but then why exact same config works in a different project of of mine in the same machine — Salman, Aug 27 '14 at 06:53
@Салман:- And what about this:- http://stackoverflow.com/questions/6865538/solving-a-communications-link-failure-with-jdbc-and-mysql — Rahul Tripathi, Aug 27 '14 at 06:53
No @R.T. I think I have given all SO answers related to this a try. — Salman, Aug 27 '14 at 06:54

weird error while creating mysql connection in jdbc

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