通信链路故障：JDBC

Question

我有一个MySqlConnection类，用于3个城市的分布式数据库。我想访问3个不同的IP，但是当程序尝试连接到节点时，JDBC会显示“通信链接失败”的异常。

代码是下一个：

public class MySqlConnection { 
    private String DB_URL;
    private String USER;
    private String PASSWORD;
    private Connection connection;    

    public Connection GetConnection(String node)
    {
        switch (node)
        {
            case "City1":
                DB_URL = "jdbc:mysql://192.168.100.8:3306/DATABASE_NAME";
                USER = "root";
                PASSWORD = "password_node1";
                break;
            case "City2":
                DB_URL = "jdbc:mysql://192.168.100.11:3306/DATABASE_NAME";
                USER = "root";
                PASSWORD = "password_node2";
                break;
            case "City3":
                DB_URL = "jdbc:mysql://192.168.100.13:3306/DATABASE_NAME";
                USER = "root";
                PASSWORD = "password_node3";
                break;
        }
        try
        {
            connection = (Connection) DriverManager.getConnection(DB_URL, USER, PASSWORD);
        }
        catch(SQLException ex)
        {
            JOptionPane.showMessageDialog(null, ex);
        }
        return connection;
    }
}

请注意，我有3台带有mysql服务器的电脑，并且所有电脑都有不同的IP。我在所有PC上都使用Ubuntu 17.04。谢谢你。