如何检查mysql连接的默认端口号?连接不工作！jdbc 连接

2022-01-24 00:00:00 connection database mysql jdbc java

我正在尝试使用 java 文件中的 jdbc 连接数据库.它根本没有连接，并且不断给我错误出了点问题"；我猜这是因为端口号，因为所有其他数据，如用户名、密码和其他代码似乎都是正确的.

I am trying to connect with database using jdbc in java file. It is not connecting at all and giving me the error constantly "Something went wrong"; I guess it is because of the port number because all other data such as username, password and other code seems correct.

我想检查默认端口号，以便我可以正确尝试.我确实尝试使用所有这三个 8080、80 和 3306，但它显示错误.

I want to check the default port number so that I can try it properly. I did try using all three of these 8080, 80 and 3306 but it shows me error.

这里8080端口用于HTTP服务器，3306应该是研究默认的，80是随机的.

Here port 8080 is used for HTTP server, 3306 is supposed to be default from the research and 80 randomly. 

try {
        Class.forName("com.mysql.jdbc.Driver");
        System.out.println("Driver found");
    } catch (ClassNotFoundException e) {
        System.out.println("Driver not found");
    }

    String url="jdbc:mysql://localhost:8080 or 80 or 3306 or without port number/test";
    String user="user";
    String password="";

    Connection con=null;

    try {
        con=DriverManager.getConnection(url, user, password);
    System.out.println("Success");
    } catch (SQLException e){
         e.printStackTrace();
    }
}

使用 String url="jdbc:mysql://localhost:3306/test";

The error is giving below when used String url="jdbc:mysql://localhost:3306/test"; 

  Driver found
  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: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:377)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1036)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:338)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2232)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2265)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2064)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:790)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:44)
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:377)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:395)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:325)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at com.town.connect.Dbconnection.main(Dbconnection.java:26)
  Caused by: java.net.ConnectException: Connection refused
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:382)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:241)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:228)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:431)
at java.net.Socket.connect(Socket.java:527)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:213)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:297)
... 15 more

推荐答案

您可以通过

mysql> show variables;

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