SOS, "IO exception: The Network Adaptor could not establish the connection." ?

[Roseanne Zhang]

I've never been a DBA, let alone Oracle DBA. However, I've to be one right now.
My Java jdbc code connected to a remote Oracle database (created by myself) w/o any problem until one day, I got an exception: "IO exception: The Network Adaptor could not establish the connection.". Since then, I always get the same exception. I thought the remote DB might have been changed by some admin people. I use a local Oracle database, (they mirror each other), then I've the same problem, I can access it from local network. I cannot access it from home or anywhere else on earth. The same exception "IO exception: The Network Adaptor could not establish the connection.".
Please help! Tell me what are the possible causes? What could go wrong? Trust me, I've searched google.com, etc.
I'm totally lost. I even tried the Sybase sample database on the web, which I used to connect on my previous job for testing purposes. No luck, I got IO exception, connection timeout. I think it is the same error with different wording. I must have done something wrong, but I don't know what is it.
I use Ant sql task to test the connection, here is the ant snippet:
For Oracle: The code works locally with the same absolute IP "***.***.**.***".

  <target name="test.db" >
    
    <sql driver="oracle.jdbc.driver.OracleDriver"
      url="jdbc:oracle:thin:@***.***.**.***:1521:mydbname"
      userid="username"
      password="password">
      <classpath>
<fileset dir="${oracle.home}"
  includes="*.jar"/>
      </classpath>
         <transaction>
           select * from tab_name;     
         </transaction> 
    </sql>     
  </target>

For sybase: The url/userid/password are all real and from sybase website.

  <target name="test.sybase" >
    
    <sql driver="com.sybase.jdbc2.jdbc.SybDriver"
      url="jdbc:sybase:Tds:192.138.151.39:4444"
      userid="guest"
      password="sybase">
      <classpath>
<fileset dir="${sybase.home}/classes"
  includes="*.jar"/>
      </classpath>
         <transaction>
           select * from tab;     
         </transaction> 
    </sql>     
  </target>
  

I'm running out of time, please help!
Thanks in advance!
Roseanne
[ November 29, 2003: Message edited by: Roseanne Zhang ]

[Roseanne Zhang]

I just setup a brand new computer, and got the same result. I think the success of remote connection is normal or opposite. Is there a security settings involved? The sybase sample database should not be behind a firewall... Confused
Please excuse my ignorance and give me a little help.

[Avi Abrami]

Hi Roseanne,

IO exception: The Network Adaptor could not establish the connection.

Usually occurs due to one (or more) of the following three things:

the database server is not running

database listener is not running

you are using the wrong URL

If you can connect to the database using SQL*Plus, then the database server is running.

Use the "lsnrctl" utility to check whether the database listener is running

Check the database configuration to find out the correct URL

Hope it helps.
Good Luck,
Avi.