SQL Developer cannot connect but SQL*plus can

Question

I have a developer who is able to connect to Oracle database using SQL*Plus from command line.

But the person is not able to connect by using SQL*Developer.

The error is as follows :

"IO Error: The network adapter could not establish the connection"

Answer 1

Here are some of the things I did to resolve the problem.

1. Download latest version of SQL*Developer ( I downloaded 17.4.0 )
2. Go to Tools -> Preferences -> Database -> Advanced
3. At the bottom of the screen look for "Oracle Client" and "Use OCI/Thick driver"
4. Press "Configure" and set Oracle client to ORACLE_HOME
5. Press "Browse" and set TNSNAMES.ORA directory

That resolved the problem.

Answer 2

First in SQL Plus, reset the SYS password by: ALTER USER SYS IDENTIFIED BY oracle ACCOUNT UNLOCK;

In the SQL Developer In the connection box, enter user name as "SYS as SYSDBA" and the password "oracle" from step 1.

This works.