How to check the default port number for mysql connection? Connection not working! jdbc connection

问题

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.

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.

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();
    }
}

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

回答1:

You can access those settings via

mysql> show variables;

回答2:

DriverManager.getConnection("jdbc:mysql://"+dbaddress+"/"+dbname+"?user=" + username + "&password=" + password)

This statement can help you. No need to define any other port. Just define the following variables as per your mysql configuration.

• dbaddress
• dbname
• username
• password

And if this doesn't works can you post the stacktrace or a screenshot for your error ?

回答3:

If you want to know the port number you can use following command

SHOW VARIABLES WHERE Variable_name = 'port';

来源：https://stackoverflow.com/questions/27702814/how-to-check-the-default-port-number-for-mysql-connection-connection-not-workin