The Network Adapter could not establish the connection in SQL developer

Question

I created a database using SQL developer list of 1000 entries and it created successfully. The connection also succeeded. But today while I'm trying to connect there is an error occurring:

IO Error: The Network Adapter could not establish the connection in SQL developer

I can surely say it is not connecting I tried it in Command prompt also in prompt it is mentioning as Protocol Adapter Error.

What is the problem here?

What is meant by Protocol Adapter Error how can i overcome it?

What is Network Adapter Error?

Answer 1

Please check the listener to see if it is down:-

ps -ef | grep tns

If you dont find the output of the listener then you have to start it. To do that type start in the LSNRCTL> prompt.

From the Oracle forum:

If the Oracle clients have been installed with 11.1.2.3 the TNS_ADMIN will be point to \user_projects\config\dbclient In that folder there should be a tnsnames.ora, if the Oracle DB is on the same machine you may want to copy the contents of database tnsnames folder to the TNS_ADMIN folder or as suggested change the environment variable.

Answer 2

You need to follow few steps .

1. Go to the directory "C:\oraclexe\app\oracle\product\11.2.0\server\network\ADMIN"

2. Open tnsnames.ora file and change the host. Generally localhost in your case

   XE =
   (DESCRIPTION =
   (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
   (CONNECT_DATA =
     (SERVER = DEDICATED)
     (SERVICE_NAME = XE)
   )
   )
   

3. Open listener.ora file and change the listener host name to localhost.

   LISTENER =
   (DESCRIPTION_LIST =
   (DESCRIPTION =
     (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
     (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
   )
   )
   

4. Open command prompt as administrator. Check for the listener status.

   c:\> lsnrctl status
   

   If you find listener is up then you can be able to connect to the sql developer. Other wise start the listener by using below command.

   c:\> lsnrctl start
   

   Now you can be able to login to sql developer without the above mentioned error.