title: Tomcat6 can't connect to MySql (The driver has not received any packets from the server)
body: <p>i'm running an Apache Tomcat 6.0.20 / MySQL 5.1.37-lubuntu / sun-java6-jdk /sun-java6-jre / sun-java6-bin  on my local machine using Ubuntu 9.10 as OS.
  I'm trying to get a simple DB-query example running for 2 days now, but i still get this Exception:</p>
  
  <pre><code>org.apache.jasper.JasperException: javax.servlet.ServletException: javax.servlet.jsp.JspException: Unable to get connection, DataSource invalid: "org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (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.)"
   org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:522)
   org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:398)
   org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
   org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
   javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
  
  root cause
  
  javax.servlet.ServletException: javax.servlet.jsp.JspException: Unable to get connection, DataSource invalid: "org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (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.)"
   org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:862)
   org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:791)
   org.apache.jsp.index_jsp._jspService(index_jsp.java:104)
   org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
   javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
   org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
   org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
   org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
   javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
  
  root cause
  
  javax.servlet.jsp.JspException: Unable to get connection, DataSource invalid: "org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (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.)"
   org.apache.taglibs.standard.tag.common.sql.QueryTagSupport.getConnection(QueryTagSupport.java:285)
   org.apache.taglibs.standard.tag.common.sql.QueryTagSupport.doStartTag(QueryTagSupport.java:168)
   org.apache.jsp.index_jsp._jspx_meth_sql_005fquery_005f0(index_jsp.java:274)
   org.apache.jsp.index_jsp._jspx_meth_c_005fotherwise_005f0(index_jsp.java:216)
   org.apache.jsp.index_jsp._jspx_meth_c_005fchoose_005f0(index_jsp.java:130)
   org.apache.jsp.index_jsp._jspService(index_jsp.java:93)
   org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
   javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
   org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
   org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
   org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
   javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
  </code></pre>
  
  <p>my web.xml looks like this :</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;web-app xmlns="http://java.sun.com/xml/ns/javaee"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
      version="2.5"&gt;
    &lt;resource-ref&gt;
        &lt;description&gt;DB Connection&lt;/description&gt;
        &lt;res-ref-name&gt;jdbc/testDB&lt;/res-ref-name&gt;
        &lt;res-type&gt;javax.sql.DataSource&lt;/res-type&gt;
        &lt;res-auth&gt;Container&lt;/res-auth&gt;
    &lt;/resource-ref&gt;
  &lt;/web-app&gt;
  </code></pre>
  
  <p>the context.xml looks like this :</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;Context path="/my1stApp" docBase="/var/www/jsp/my1stApp" debug="5" reloadable="true" crossContext="true"&gt;
      &lt;Resource name="jdbc/testDB" auth="Container" type="javax.sql.DataSource"
      maxActive="5" maxIdle="5" maxWait="10000"
      username="user" password="password" driverClassName="com.mysql.jdbc.Driver"
      url="jdbc:mysql://localhost:3306/some"/&gt;
  &lt;/Context&gt;
  </code></pre>
  
  <p>and the jsp file looks like this:</p>
  
  <pre><code>&lt;%@ page contentType="text/html" %&gt;
  
  &lt;%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %&gt;
  
  &lt;%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %&gt;
  
  &lt;%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %&gt;
  &lt;%@ taglib prefix="sql" uri="http://java.sun.com/jsp/jstl/sql" %&gt;
  
  
  &lt;html&gt;
  
    &lt;head&gt;
  
      &lt;title&gt;DroneLootTool&lt;/title&gt;
  
    &lt;/head&gt;
  
    &lt;body bgcolor="white"&gt;
  
  
  
   &lt;sql:query var="res" dataSource="jdbc/testDB"&gt;
    select name, othername 
    from mytable
   &lt;/sql:query&gt;
  
    &lt;h2&gt;Results&lt;/h2&gt;
  
  &lt;c:forEach var="row" items="${res.rows}"&gt;
      Name ${row.name}&lt;br/&gt;
      MoreName ${row.othername}&lt;br/&gt;&lt;br/&gt;
  &lt;/c:forEach&gt;
  
  
    &lt;/body&gt;
  
  &lt;/html&gt;
  </code></pre>
  
  <ul>
  <li>read lots of forum entries / tried lots of different settings (always changed back to original settings when it didnt' work)</li>
  <li>set TOMCAT6_SECURITY=no in /etc/default/tomcat6 because TOMCAT6_SECURITY=yes was causing trouble too</li>
  <li>the skip-networking flag is not set for the DB (BIND 127.0.0.1 is set)</li>
  <li>firewall is swiched off (sudo ufw disable)</li>
  <li>MySQL works (tested several times with user used in this skript)</li>
  <li><p>telnet localhost 3306 says</p>
  
  <p>Trying ::1...
  Trying 127.0.0.1...
  Connected to localhost.
  Escape character is '^]'.
  Connection closed by foreign host.</p></li>
  </ul>
  
  <hr>
  
  <p>The TestConnection.java produced the following output:</p>
  
  <p>me@my-laptop:~/Desktop$ java -classpath '/usr/share/java/mysql.jar:./' TestConnection com.mysql.jdbc.Driver jdbc:mysql://localhost:3306/testDB myuser mypassword</p>
  
  <pre><code>com.mysql.jdbc.CommunicationsException: Communications link failure
      Last packet sent to the server was 0 ms ago.
          at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1070)
          at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2103)
          at com.mysql.jdbc.ConnectionImpl.&lt;init&gt;(ConnectionImpl.java:718)
          at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:298)
          at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:282)
          at java.sql.DriverManager.getConnection(DriverManager.java:582)
          at java.sql.DriverManager.getConnection(DriverManager.java:185)
          at TestConnection.checkConnection(TestConnection.java:40)
          at TestConnection.main(TestConnection.java:21)
      Caused by: com.mysql.jdbc.CommunicationsException: Communications link failure
  
      Last packet sent to the server was 0 ms ago.
          at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1070)
          at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:666)
          at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1069)
          at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2031)
          ... 7 more
      Caused by: java.io.EOFException: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.
          at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2431)
          at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:590)
          ... 9 more
      Connection failed.
  </code></pre>
  
  <hr>
  
  <p>i don't know if there is a difference between the way the java driver connects to the DB and the Perl DBI module does, but this PERL skript works</p>
  
  <pre><code>#!/usr/bin/perl -w 
  
  use CGI;
  use DBI;
  use strict;
  
  print CGI::header();
  
  my $dbh = DBI-&gt;connect("dbi:mysql:some:localhost", "user", "password");
  
  my $sSql = "SELECT * from mytable";
  
  my $ppl = $dbh-&gt;selectall_arrayref( $sSql );
  
  foreach my $pl (@$ppl)
  {
    my @array = @$pl;
    print @array;
  }
  
  $dbh-&gt;disconnect;
  </code></pre>
  
  <hr>
  
  <p>enabled --log-warnings on the mysql, but i didn't get any new warnings.
  When i was searching the logs for warnings i found this messages when i restart the tomcat, don't know if it helps to find the problem :</p>
  
  <pre><code>Feb  2 19:50:37 tobias-laptop jsvc.exec[3129]: 02.02.2010 19:50:37 org.apache.catalina.startup.HostConfig checkResources#012INFO: Undeploying context [/myapp]
  Feb  2 19:50:37 tobias-laptop jsvc.exec[3129]: 02.02.2010 19:50:37 org.apache.catalina.loader.WebappClassLoader clearReferencesThreads#012SCHWERWIEGEND: A web application appears to have started a thread named [MySQL Statement Cancellation Timer] but has failed to stop it. This is very likely to create a memory leak.
  Feb  2 19:50:37 tobias-laptop jsvc.exec[3129]: 02.02.2010 19:50:37 org.apache.catalina.startup.HostConfig deployDescriptor#012INFO: Deploying configuration descriptor myapp.xml
  </code></pre>