You can read the audit logs using this sample: https://doc.developer.milestonesys.com/html/index.html?base=samples/componentsamples/logread/readme.html&tree=tree_search.html?search=logread
The server does not keep a list of who is currently logged-in, so the only way to know is reading the logs. Logging is low priority and there can be a long wait from a login to a log update.
The server does log users if they are logging in using a MIP SDK based application same way exactly as the user using the Smart Client.