Today I killed 2 hours of my life for very studip problem.

I just got new notebook (IBM Thnkpad T400) with 4Gb, so, to be able to use whole memory, installed Ubuntu 10.04 64 bit. Then installed mysql-server, sun java, eclipse, some other staff and started to work. mysql nd sun java was installed via apt with standard settings.

Created DB, successfully connected via MySQL Admin and Query Browser, and, then, trying to connect from my app: failed

Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

Last packet sent to the server was 0 ms ago.
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

Checking JDBC Url - everything is correct, checking username/password - same, I can connect to localhost DB with using this username/password with using standard mysql tools. But not from java via JDBC.

WTF???

After spending 2 hours, found this forum. After commenting bind-address in my.cnf and changing jdbc url to use my computer IP address (like 192.168.0.157) instead of localhost it finally started to connect.

Why? Why it is not working with localhost out-of-box? Why I should spent 2 hours for such stupid problems?

Problem resolved

Ok, today (after sleeping a little bit) I realized the source of problem. It is not ubuntu, java, or mysql. It is (of course) - I'm.

Yesterday I changed by /etc/hosts - so, localhost was defined incorrectly (by some reason). But, MySQL clients, in case localhost server used - not used TCP at all - then connected to mysql directly.

JDBC driver does not use it - it always (looks like) tried to use TCP and resolve hostname. It is why it connection worked in mysql tools, but did not worked in java.

Ubuntu == cool!

Java == cool!

I'm == dummy developer :)