How to find open connections with Oracle database

If you want to know the open or active or inactive connections with Oracle DB,
1. Login to that Oracle schema (may be through Toad or Oracle etc) and
2. Run below sql
select sid,serial#,PROGRAM,machine,TO_CHAR(logon_Time,'DD-MON-YYYY HH24:MI:SS') AS logon,status from v$session where username='userNameWhichIWouldHaveUsedToConnect';