Exception in thread "main" 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 java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
 at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
 at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
 at java.base/java.lang.reflect.Constructor.newInstance(Unknown Source)
 at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
 at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:990)
 at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:342)
 at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2188)
 at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2221)
 at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2016)
 at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:776)
 at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
 at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
 at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
 at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
 at java.base/java.lang.reflect.Constructor.newInstance(Unknown Source)
 at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
 at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:386)
 at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:330)
 at java.sql/java.sql.DriverManager.getConnection(Unknown Source)
 at java.sql/java.sql.DriverManager.getConnection(Unknown Source)
 at Test.main(Test.java:42)
Caused by: java.net.ConnectException: Connection refused: connect
 at java.base/java.net.DualStackPlainSocketImpl.connect0(Native Method)
 at java.base/java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
 at java.base/java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
 at java.base/java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
 at java.base/java.net.AbstractPlainSocketImpl.connect(Unknown Source)
 at java.base/java.net.PlainSocketImpl.connect(Unknown Source)
 at java.base/java.net.SocksSocketImpl.connect(Unknown Source)
 at java.base/java.net.Socket.connect(Unknown Source)
 at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:211)
 at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:301)


이런거 뜨는데 하루종일 찾아서 하고 있는데 도저히 모르겠어..


우분투 서버를 새로 구축하고 하고 있는데 뭐를 건드려야 할까?