无法使用jdbc连接到mysql服务器

Question

  

可能重复：
  com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

我有一个使用jdbc连接到mysql数据库的java程序。它以前工作过，现在却没有。这是tomcat catalonia.out日志中的错误：

Cannot connect to database server
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.GeneratedConstructorAccessor8.newInstance(Unknown Source)
    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:411)
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1116)
    at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:696)
    at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1102)
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2336)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2369)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2153)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:792)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
    at sun.reflect.GeneratedConstructorAccessor10.newInstance(Unknown Source)
    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:411)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:381)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)
    at java.sql.DriverManager.getConnection(DriverManager.java:582)
    at java.sql.DriverManager.getConnection(DriverManager.java:185)
    at web.DBConnectionDesign.<init>(DBConnectionDesign.java:33)
    at web.SaveDatabase2.doPost(SaveDatabase2.java:126)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
    at java.lang.Thread.run(Thread.java:619)
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:2552)
    at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:620)
    ... 30 more

这是尝试连接数据库的代码

public DBConnectionDesign() {
// Create a database connection
    String account = "account";
String password = "password";
String server = "localhost:3306";
String database = "database";
try {
    Class.forName("com.mysql.jdbc.Driver");

    con = DriverManager.getConnection
        ( "jdbc:mysql://" + server, account,password);
        System.out.println ("Database connection established");
    stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,     ResultSet.CONCUR_UPDATABLE);
    stmt.executeQuery("USE " + database);
    // get the column names; column indexes start from 1        
    } catch (SQLException e) {
        System.err.println ("Cannot connect to database server");
        e.printStackTrace();
    } 
    catch (ClassNotFoundException e) {
        e.printStackTrace();
    }

}

我可以使用终端上的相同用户名和密码访问数据库。我还有一个wordpress站点，可以访问同一台服务器上的另一个mysql数据库。这是my.conf：

[client]
port            = 3306
socket          = /var/run/mysqld/mysqld.sock

[mysqld_safe]
socket          = /var/run/mysqld/mysqld.sock
nice            = 0

[mysqld]

user            = mysql
socket          = /var/run/mysqld/mysqld.sock
port            = 3306
basedir         = /usr
datadir         = /var/lib/mysql
tmpdir          = /tmp
skip-external-locking

bind-address            = 127.0.0.1
key_buffer              = 16M
max_allowed_packet      = 16M
thread_stack            = 192K
thread_cache_size       = 8

myisam-recover         = BACKUP

query_cache_limit       = 1M
query_cache_size        = 16M

general_log_file        = /var/log/mysql/mysql.log
general_log             = 1

log_error                = /var/log/mysql/error.log

expire_logs_days        = 10
max_binlog_size         = 100M

[mysqldump]
quick
quote-names
max_allowed_packet      = 16M

[mysql]

[isamchk]
key_buffer              = 16M

如果有人想要检查其他错误日志，或者如何正确使用tcpdump来查看请求，我会非常感激。现在，我不知道为什么我无法连接到服务器：端口号是正确的，用户名和密码也是正确的。如何找出无法连接服务器的原因？

谢谢！