Error:Network Adapter could not establish the connection

[vamsi naki]

Hi,
I installed Oracle SQL Developer ,i am trying to create a new connection but i am getting this error message "The Network Adapter could not establish the connection".
The hostname is :localhost
port:1521
SID:xe

[Jeanne Boyarsky]

Is Oracle running? (check Windows services or "ps" on UNIX.) Is the database in your tns file? Does it work at the command line?

[vamsi naki]

Oracle is running ,i checked it in the task manager .I dont know what a tns file is .This is my first time installing or running oracle ,i just have a basic idea of some of the oracle commands.The oracle sql developer tool is opening when i run through command prompt .