You can start or stop the TFTP service by clicking on the Start/Stop button: it will change its icon and text to reflect the server's status, also visible in the status area at the bottom of the TftpServer window.
You can also change the TFTP server working path by either clicking the Change Path button and browsing to select a new path or typing the new path in the path text field and hitting the [Enter] key (in the latter case the application will check whether the path you have just typed is correct or not). After the path is changed, the outline view will be consequently updated to display the contents of the newly selected folder.
Please note that the name of the folder that you wish to use as TFTP working folder and those of all its parent folders must not contain spaces, parenthesis or other punctuation or special characters, thus you can only use names with letters, numbers or dashes, otherwise the TftpServer application will not allow you to select such a folder.
You can easily open a new Finder window displaying the current TFTP working folder's content clicking the Reveal in Finder button.
If you need to upload a new file to your TFTP server, click the Create File button and type the name of the file to upload: a new empty file with the correct permissions already set will be created (this is mandatory if you have to upload a file to your Mac via TFTP, see here for more info); here you also have the choice to set the file creator to BBEdit for the new file (or any other app of your choice, but you need to know its 'classic' app creator 4-chars code), otherwise TextEdit is the default app that will open it.
Click the Refresh button to update either the current path's outline or the Log Viewer.
There are also two other toolbar buttons, not present in the default toolbar, that may be useful when dealing with Cisco IOS devices: Copy to tftp: and Copy from tftp: These buttons are active only when a file is selected and they can be used to copy to the clipboard the Cisco IOS command that you can paste in a Terminal window where you are connected to a Cisco device to copy its startup-config respectively to and from you Mac runing a TFTP server (e.g. copy startup-config tftp://192.168.1.10/router-confg).
To the right of the TFTP working path you can find a popup button with a list of the network interfaces configured on your Mac and their IP addresses with the primary interface listed first; selecting a different interface its IP address is automatically copied to the clipboard: this may be useful when you have to manually upload/download a file using tftp.
Double clicking on a file listed in the current path's outline view you can open it with its default application, like when you double-click a file in a Finder window. Moreover, if you select a file and hit [Cmd]-C (the standard shortcut for Copy) the selected file name will be copied to the clipboard.
In the Log Viewer we used to find some useful info about the TFTP service and its activity, e.g. when and how its configuration has been changed, when the service has been started/stopped and when an external device attempts to upload/download a file. This data is extracted from both the Console.log and System.log files but since Mac OS X 10.4 Apple has broken something and the only information we can actually get from such log files is just when the service is started or stopped: I have tried in all ways to force the TFTP daemon to log more stuff than this, but to no avail.
At the bottom of the TftpServer window you are noticed about the server status and whether the permissions of both the current TFTP working folder and its parent folders are properly set; if needed, you can click on the appropriate Fix button and the application will automatically set the correct permissions as described in the About TFTP section.