Is there a MySQL server running on the machine/port you are trying to connect to?

Hello!

I relatively new to Java, and am currently working on a project, for which I would like to be able to connect to an online mySQL database. One that's being hosted somewhere ... else.

For days, I have been trying to figure out why it won't work. I have tried countless tutorials on J/Connector, and they all come up with the same error;

Is there a MySQL server running on the machine/port you are trying to connect to?

In my last attempt, I have followed this tutorial, word for word.

Connecting to localhost failed, as did to GoDaddy, and FreeMySql.net, and even a public genome database.

The people over at the Java forums didn't help at all, so I come here seeking dire assistance.

Not sure what code to post, as I have tried so much, and it all comes down to the same error.

Thanks in advance!

Not sure what code to pos

Post your connection string, and complete error messages.
Regards, Jan

Are you able to use the mysql command line tools to connect to the remote database?

Also, since you are just now starting out with JDBC, I would recommend that your install MySQL locally and work with that. Most tutorials assume that you will have a local MySQL database and thus use 'localhost' in the URL. Once you are comfortable with coding for your local database you can easily substitute the URL for for local database with the one for the remote database.

Well, here is the code;

import java.sql.*; 
public class dbCon { 
    public static void runMe (String host, String database, String user, String password) 
      throws Exception { 
         
        /* run driverTest method shown below */ 
        driverTest(); 
         
        /* make the connection to the database */ 
        Connection conMe = makeCon (host, database, user, password);

/* now run a select query of the intended database */ 
        exeQuery (conMe, "SELECT * FROM comments"); 
         
        /* close the database */ 
        conMe.close(); 
    } 
	protected static Connection makeCon (String host, String database, String user, String password) 
          throws Exception {

String url = ""; 
            try { 
                url = "jdbc:mysql://localhost:3306/feedback"; 
                  Connection con = DriverManager.getConnection(url, user, password); 
            System.out.println("Connection established to " + url + "..."); 
            return con; 
            } catch (java.sql.SQLException e) { 
            System.out.println("Connection couldn't be established to " + url); 
            throw (e); 
            } 
    }
    protected static void driverTest () throws Exception {

try { 
                        Class.forName("org.gjt.mm.mysql.Driver"); 
                        System.out.println("MySQL Driver Found"); 
                } catch (java.lang.ClassNotFoundException e) { 
                        System.out.println("MySQL JDBC Driver not found ... "); 
                        throw (e); 
                } 
              } 
    protected static void exeQuery(Connection con, String sqlStatement) 
          throws Exception {

try { 
                        Statement cs = con.createStatement(); 
                        ResultSet sqls = cs.executeQuery(sqlStatement);

while (sqls.next()) { 
                                String id = (sqls.getObject("id").toString()); 
                                String data = (sqls.getObject("data").toString()); 
                                System.out.println(id + " " + data); 
                        }

sqls.close();

} catch (SQLException e) { 
                        System.out.println ("Error executing sql statement"); 
                        throw (e); 
                } 
    } 
    public static void main (String arg[])throws Exception {
    	runMe("localhost", "mysql", "root", "");
    } 
/* this bracket closes the class */ 
}

And here is my JCreator output;

MySQL Driver Found
Connection couldn't be established to jdbc:mysql://localhost:3306/feedback
Exception in thread "main" java.sql.SQLException: Cannot connect to MySQL server on localhost:3306. Is there a MySQL server running on the machine/port you are trying to connect to? (java.lang.NumberFormatException)
at com.mysql.jdbc.Connection.connectionInit(Unknown Source)
at com.mysql.jdbc.jdbc2.Connection.connectionInit(Unknown Source)
at com.mysql.jdbc.Driver.connect(Unknown Source)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at dbCon.makeCon(dbCon.java:24)
at dbCon.runMe(dbCon.java:10)
at dbCon.main(dbCon.java:63)

Process completed.

Well, I use Navicat to connect to mySQL servers, and they work fine.

As for localhost, yeah, I have tried that several times, unfortunately to no avail.

From the stack trace, it seems that the MySQL server is not running at localhost:3306
Connection couldn't be established to jdbc:mysql://localhost:3306/feedback
Exception in thread "main" java.sql.SQLException: Cannot connect to MySQL server on localhost:3306. Is there a MySQL server running on the machine/port you are trying to connect to?
You can do a telnet and check if MySQL is up or dead. Open your command prompt/linux console and run this cmd.
telnet localhost 3306
If it says.. "Connection refused or something similar", then MySQL service is not started. To start mysql on linux you can run
/etc/init.d/mysql start
If connection was successful, then check if you have created a database 'feedback' in mysql which you are connecting in your code.
Hope this helps

The problem is that you are using "localhost" in the connection URL. As you stated in your original post you are using a remote mysql server. You need to find out from that mysql provider what URL you should be using. If they don't know the URL, ask them for the host name and port number. I assume that you know the database. From that information you can build the connection URL.

The alternative is to follow my suggestion and install MySQL locally. I highly recommend that!