NET.exe - NET SESSION and NET FILE

The NET command is used to manage open files and user sessions.

Syntax
      NET SESSION [\\computername [/DELETE] | /LIST]

      NET FILE [id [/CLOSE]]
Key
   computername    A computer whose shared resources you want to view. 
   domainname      The domain to view, by default all domains in the LAN.
   /DELETE         End the session and close all open files for that session,
                   if computername is omitted all sessions are ended.
   /LIST           Display information in a list rather than a table.
   id              The identification number of the file.
   /CLOSE          Close an open file and remove file locks

Display all the open shared files on a server and the lock-id
NET FILE

Close a shared file (disconnect other users and remove file locks) type this command from the server where the file is shared.
NET FILE id /CLOSE

List all sessions connected to this machine:
NET SESSION
or
NET SESSION | Find "\\"

List sessions from a given machine
NET SESSION \\ComputerName

Disconnect all sessions connected to this machine
NET SESSION /DELETE

Disconnect all sessions connected to this machine (without any prompts)
NET SESSION /DELETE /y

Disconnect sessions from a given machine
NET SESSION \\ComputerName /DELETE

NET SESSION displays incoming connections only, in other words it must be run on the machine that is acting as the server.

To create file shares the SERVER service must be running, which in turn requires 'File and Print Sharing' to be installed.

UAC elevation

Administrator privileges are required to run the NET SESSION command, if run from a non-elevated session it will return an ERRORLEVEL = 5 Access is Denied.

NET SESSION requires the Server service to be running

“Never mistake activity for achievement” ~ John Wooden

Related:

NET - Manage network resources.
NET USE - connect to a file share.
OPENFILES - List or disconnect open files, local or remote.
PsFile - Show files opened remotely.
PsLoggedOn - Who's logged on.
Q149427 - Change Password from the CMD prompt.
Powershell: Get-WmiObject win32_share
Equivalent bash command (Linux): who currently logged in.