-- Get a count of SQL connections by IP address
SELECT
   ec.client_net_address,
   es.[program_name],
   es.[host_name],
   es.login_name,
   COUNT(ec.session_id) AS [connection count]
FROM sys.dm_exec_sessions AS es  
INNER JOIN sys.dm_exec_connections AS ec  
   ON es.session_id = ec.session_id  
GROUP BY
   ec.client_net_address,
   es.[program_name],
   es.[host_name],
   es.login_name  
ORDER BY
   ec.client_net_address,
   es.[program_name];

-- Get a count of SQL connections by login_name
SELECT
   login_name,
   COUNT(session_id) AS [session_count]
FROM  sys.dm_exec_sessions
GROUP BY login_name
ORDER BY login_name;