java.sql.SQLException: Io 异常:The Network Adapter could not establish the connect

package com.bjpowernode.drp.util;import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;public class DbUtil {

public static Connection getConnection(){
Connection conn = null;
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
conn = DriverManager.getConnection("jdbc:oracle:thin:@127.0.0.1:1521:bjpowernode","drp","yanyu");
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
System.out.println("连接异常！");
e.printStackTrace();
}
return conn;
}

public static void main(String args[]){
System.out.println(DbUtil.getConnection());
}
}
总是出现连接错误的问题，错误如下：
java.sql.SQLException: Io 异常: The Network Adapter could not establish the connection连接异常！ at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:112)
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:146)
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:255)
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:387)
at oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:414)
at oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:165)
at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:35)
at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:801)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at com.bjpowernode.drp.util.DbUtil.getConnection(DbUtil.java:14)
at com.bjpowernode.drp.util.DbUtil.main(DbUtil.java:27)
null
但是我把conn = DriverManager.getConnection("jdbc:oracle:thin:@127.0.0.1:1521:bjpowernode","drp","yanyu");中的127.0.0.1改成192.168.16.2就连接成功了，但是改成127.0.0.1或者localhost都不行，出现上面的错误，使用的数据库是oracle10g，哪位高手给解读下这是咋回事啊？