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Asked: 2026-05-11T00:26:55+00:00

Pretty straightforward stuff, here — I’m just not good enough with mysql to understand

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Pretty straightforward stuff, here — I’m just not good enough with mysql to understand what it wants from me.

I’ve got a short java test-case that opens a connection on mysql on my dev system but, when I try to put it to my server, it fails.

Any help in tracking this down would be most appreciated.

Thanks!

Test Code

import  java.util.*; import  java.sql.*;  public  class   mysqltest {      static  public  void  getDBConnection() {         System.out.println ('Start of getDBConnection.');          Connection  conn        = null;         String      url         = 'jdbc:mysql://localhost:3306/';         String      dbName      = 'magnets_development';         String      driver      = 'com.mysql.jdbc.Driver';         String      userName    = '*****';  // blanked for publication         String      password    = '*****';          try {             Class.forName (driver).newInstance();             System.out.println ('driver.newInstance gotten.');             conn = DriverManager.getConnection (url+dbName, userName, password);             System.out.println ('Connection gotten: ' + conn + '.');             Statement sql     = conn.createStatement ();             ResultSet results = sql.executeQuery ('use ' + dbName + ';');         }         catch (Exception ex) {             System.out.println ('*** Got exception.');             ex.printStackTrace();         }     }      public static void main(String args[]) {         System.out.println ('Main started.');         mysqltest.getDBConnection();     } }

Dev System Output (Expected/correct response)

olie$ java mysqltest Main started. Start of getDBConnection. Properties set. driver.newInstance gotten. Connection gotten: com.mysql.jdbc.Connection@c980c9. olie$

Server Output (Error I’m trying to track-down) (Some blank lines removed.)

mini$ java mysqltest Main started. Start of getDBConnection. Properties set. driver.newInstance gotten. *** Got exception. com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception:   ** BEGIN NESTED EXCEPTION **   java.net.ConnectException MESSAGE: Connection refused  STACKTRACE:  java.net.ConnectException: Connection refused     at java.net.PlainSocketImpl.socketConnect(Native Method)     at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)     at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)     at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)     at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:432)     at java.net.Socket.connect(Socket.java:520)     at java.net.Socket.connect(Socket.java:470)     at java.net.Socket.<init>(Socket.java:367)     at java.net.Socket.<init>(Socket.java:209)     at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:256)     at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:271)     at com.mysql.jdbc.Connection.createNewIO(Connection.java:2771)     at com.mysql.jdbc.Connection.<init>(Connection.java:1555)     at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)     at java.sql.DriverManager.getConnection(DriverManager.java:525)     at java.sql.DriverManager.getConnection(DriverManager.java:140)     at mysqltest.getDBConnection(mysqltest.java:34)     at mysqltest.main(mysqltest.java:49)  ** END NESTED EXCEPTION **  Last packet sent to the server was 3 ms ago.     at com.mysql.jdbc.Connection.createNewIO(Connection.java:2847)     at com.mysql.jdbc.Connection.<init>(Connection.java:1555)     at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)     at java.sql.DriverManager.getConnection(DriverManager.java:525)     at java.sql.DriverManager.getConnection(DriverManager.java:140)     at mysqltest.getDBConnection(mysqltest.java:34)     at mysqltest.main(mysqltest.java:49) mini$
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1 Answer

  1. Bah! My apologies — I just had ‘local connections only’ set up. I was confused by the fact that the java app was running locally (so seemed a ‘local connection’ but, because it is connecting via TCP, it’s a ‘remote’ connection, even though it originates on localhost.

    I will eventually learn how to administer these things. In the mean time, I hope someone else can learn from my mistakes.

    Thank you to all who put time into trying to help me. I have since allowed ‘remote’ connections, but all of my user-accounts are ‘username’@’localhost’ only (i.e., there is no ‘username’@’%’, which would allow any machine to connect.) Hopefully, I got that part right, at least.

    Thanks again!

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