cannot connect my oracle server to developer
First Logged in SQLPlus and Unlock the user

Run SQLPlus, connect as SYS user (use administrator's password you have entered during installation) . Suppose that here For your test connection unlock HR user and give him a new password:

C:\&gt;sqlplus  sys as sysdba

SQL*Plus: Release 12.1.0.2.0 Production on Wed Jan 24 12:15:51 2018

Copyright (c) 1982, 2014, Oracle.  All rights reserved.

Enter password:

Connected to:
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options

SQL&gt; alter user hr identified by new_password;

User altered.

SQL&gt; alter user hr account unlock;

User altered.


For Creating a Database Connection

The first step to managing database objects using Oracle SQL Developer is to create a database connection.Perform the following steps:


Open Oracle SQL Developer.
In the Connections navigator, right-click Connections and select New Connection.
Enter test for the Connection Name (or any other name that identifies your connection), hr for the Username and Password, specify your localhost for the Hostname and enter ORCL10(in your case, as it showing in your attached picture) for the SID. Click Test.
The status of the connection was tested successfully. The connection was not saved however. Click Save to save the connection, and then click Connect.


For further your ref Here , Here &amp; Here