mjaga mjaga - 5 months ago 12
MySQL Question

failure to connect to mysql from java locally while remote connection works

I have the following situation:

I can


  • connect to my mysql database via the command line tool mysql, both from the local machine and a remote host

  • connect from a small java test program from the remote host



I can not


  • connect from that same small java test program from the local machine



The test code is basically the same as in this question and I followed all the suggestions given there to solve my problem with no avail. I have tried the following connection strings:


  1. jdbc:mysql://localhost/database

  2. jdbc:mysql://localhost:3306/database

  3. jdbc:mysql://127.0.0.1/database

  4. jdbc:mysql://hostname/database



all resulting in the same error message. On the remote machine I could use the fourth alternative with no problem.

I am running a mysql-5.5 server. The remote uses java version "1.7.0_101" and the local machine has java version "1.6.0_38".

Here is the error message when I run my java program on the local machine:

Connecting to database...
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: 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.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:534)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1116)
at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:688)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1094)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2337)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2370)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2154)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:792)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:534)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:381)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)
at java.sql.DriverManager.getConnection(DriverManager.java:615)
at java.sql.DriverManager.getConnection(DriverManager.java:195)
at FirstExample.main(FirstExample.java:22)
Caused by: java.io.EOFException: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.
at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2540)
at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:612)
... 16 more
Goodbye!

Answer

I just realized that mysql -u user database would work, but not mysql -u user -h 127.0.0.1 database, so it turned out I had an error in my /etc/hosts.allow file. Problem solved!