In Mac OS 9, you can share files across a network with the File Sharing control panel; you can also monitor what's going on out on the network with the control panel's Activity Monitor tab.

A list of connected users appears at the top, and a list of shared folders and disks appear at the bottom. To disconnect a user at any time, select his or her name on the list and then click the Disconnect button. A dialog box appears, asking you how many minutes until the selected user is disconnected. Type in a number and click OK; when time is up, that user is disconnected.

If you type 0 in the disconnect dialog box, the user is disconnected immediately. Before you disconnect anyone from your computer, be sure to check with him or her to make sure they save whatever work their doing.

The activity monitor at the bottom of the screen tells you how much activity is on the network. If yours is always up in the busy range, you may need to rethink your network strategy.