io 错误：网络适配器无法建立连接

Question

I am developing a mini project using Java and Oracle XE database. I was able to connect to database, insert, update and run all other queries from my personal computer, but when I tried to run the same program on my college computer (which is networked) it did not run and gave me the following exception message:

io error:network adapter could not establish the connection

I tried researching the error message on the internet and found that it must be a firewall or port number problem, but I am unable to sort it. How can I fix this error?

Here is the connection code that I used:

public void connect()
{
    try
    {
        Class.forName("oracle.jdbc.driver.OracleDriver");
        conn=DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:XE","system","system");
    }
    catch(Exception e)
    {
        JOptionPane.showMessageDialog(this, e.getMessage());
    }
}

SimpleDateFormat sd=new SimpleDateFormat("dd-MM-yy");
DefaultTableModel table_allrec;
PreparedStatement pstmt,pstmt1;
Connection conn;
ResultSet rs,rs1;

Answer 1

This error is most likely caused by one of these factors:

• You are using the wrong URL

• The wrong port number or IP address (or DNS host name) was used

• The listener is not configured properly

• The listener process (service) is not running. You can re-start it with the "lsnrctl start" command or on Windows by starting the listener service.

Answer 2

1. Please make sure, you are entering correct username, password, hostname, PORT, SID while creating connection in SQL Developer

2. On the machine where DB is installed, go to this folder C:\\app{{Username_machine}}\\product\\11.2.0\\dbhome_1\\NETWORK\\ADMIN

PS : {{Username_machine}} : This is will differ from machine to machine

3. Open 2 files inside this listener.ora AND tnsnames.ora

4. Check hostname, PORT, SID mentioned in the files MUST match with the one you are trying to use in STEP 1.

5. If any of the value doesn't match, Use the values present in the 2 Files for creating connection in SQL Developer

6. Try to connect with updated values in case mismatch of values were found

7. If you are still not able to connect

8. press windows + R, and type services.msc -- this is will open Services running on your machine

9. restart all the services that are starting with oracle

10. Try to reconnect again on SQL Developer

11. If it fails again,

12. Open CMD in administrative mode,

13. Check if Your TNS Listener is up by typing the following command lsnrctl status

14. The above command will give error if the Listener is not up

15. Start the Listener, by typing the following command, lsnrctl start

16. In case you are having problems in starting your listener then try starting “OracleOraDb11g_home1TNSListener” windows service. For that open your Run Command and write services.msc this will open your service panel. Here search for the same and right click to start it.

17. Doing the above steps, will resolve your Problem. Thanks !