I am using SQL Server 2008 Enterprise. I want to see any active SQL Server connections, and the related information of all the connections, like from which IP address, connect to which database or something.
Are there existing commands to solve this issue?
You can use the sp_who stored procedure.
Provides information about current users, sessions, and processes in an instance of the Microsoft SQL Server Database Engine. The information can be filtered to return only those processes that are not idle, that belong to a specific user, or that belong to a specific session.
Apart from sp_who, you can also use the "undocumented" sp_who2 system stored procedure which gives you more detailed information. See Difference between sp_who and sp_who2.
Click the "activity monitor" icon in the toolbar.
In SQL Server Management Studio, right click on Server, choose "Activity Monitor" from context menu -or- use keyboard shortcut Ctrl + Alt + A.
Reference: Microsoft Docs - Open Activity Monitor in SQL Server Management Studio (SSMS)
MS's query explaining the use of the KILL command is quite useful providing connection's information:
SELECT conn.session_id, host_name, program_name,
nt_domain, login_name, connect_time, last_request_end_time
FROM sys.dm_exec_sessions AS sess
JOIN sys.dm_exec_connections AS conn
ON sess.session_id = conn.session_id;
You can perform the following T-SQL command:
SELECT * FROM sys.dm_exec_sessions WHERE status = 'running';