JDBC 连接远程mysql问题

[ANoTher_O]

tomcat 可以连接本地数据库
可以连接局域网数据库
但是连接外网数据库报错

MySQL操作错误
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet successfully received from the server was 18,904 milliseconds ago. The last packet sent successfully to the server was 18,904 milliseconds ago.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1121)
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3673)
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3562)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4113)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2570)


是超时什么的还是是什么别的原因 是链接程序需要加点什么 还是远程的mysql需要设置