How to remote access Oracle 12c using SQL Developer? The listener has started correctly and its status shows OK!

I enter the correct IP address of the server in the listener.ora file, not localhost.

But when I try to connect to my database by entering the following in SQL Developer:

user: system
password: *******

host: 54.215.5.46
port: 1521
SID: orcl


I get this error: 


  Statut : échec -Echec du test : Erreur d'E/S: The Network Adapter could not establish the connection


I think that I need to open the 1521 port but I don't know if this is the problem?
You need to check the following in-order to connect to remote database:


Make sure server is accessible from client side, easiest way to do it by using ping command to verify.
There is a connection between host and server using a specific port, you can use telnet command to verify.
Enable the instance listener to be listening on an IP address not localhost.
Database is running