IO Error: The network adapter could not establish the connection

I'm not sure if the following steps will help you or not to solve the "IO Error: The network adapter could not establish the connection" issue just give a try it works in my case.

The error  was:

(In NetBeans and in Sqldeveloper)

Steps:

Step 1: Open CMD
Step 2: Type services.msc and hit enter

Step 3: Search for Oracle Services and make sure that the following three are running:
                                             OracleXETNSListener
                                             OracleXEClrAgent
                                             OracleServiceXE

Step 4: If not then just right click and hit start

That's all :).

Hope This will help you :p.