DB connection failed on local machine

Hi
In cloud computing; I use Oracle 11g database. I can access it in the browser.
But I fail to make connection in DB from my local machine (both thru JDEV and Java Program). It shows an error: 'Network Adapter could not establish the connection'.
All the requirements such as credentials, host name, port name, SID are correct. But, I am not able to connect. What is the reason? Please solve my problem. Thanks in advance.
