Port 1352

The catch with using the file transfer feature in Sametime is that there are two types of file transfers:  "client-to-client" and "through the Sametime server."  The default policy causes the client to use the client-to-client method and will not fail over to the other method if the latter does not succeed (and doesn't give the indication to the user if the file isn't going to route; leaving them with the opposite of the warm-fuzzy feeling).

Here's how IBM explains it:  If you enable "Allow client-to-client file transfer" and two users are unable to transfer files client-to-client, the file transfer does not automatically change to file transfer through the Sametime server. The file does not get transferred.

Too bad the client can't attempt to send a test packet and quickly warn a user that their client-to-client file transfer isn't going to work... or fail over to the alternative method... or present them with some other indication of what's going on... or...

Even if client-to-client transfer works in your environment, you might consider changing your policy to use the other method.  Your local paid-paranoid IT security manager will probably flip with the realization that files passed client-to-client are not logged.  (I know, neither are transfers via usb drives, and CDs, and...)

So, without further ado, here's how to prevent client-to-client transfers (destined for failure or not) and enable transfers through the server (set the other related settings you'll see in the following menus to match your needs):

1. Log in to your Sametime web site as an administrator.
2. Click "Administer the server."
3. Click Policies.
4. Click the user policy whose members you want to allow file transfers.  For this example, I'm editing the "Sametime Default Policy."
5. In the "Community Services" section, verify the "Allow file transfer" box is checked.
6. In the same section, verify the "Allow client-to-client file transfer" box is unchecked.
7. Click OK.
   
8. Click Configuration > Community Services.
9. On the "Community Services" tab, "Server Features" section, verify that "Allow users to transfer files to each other" has been enabled.
10. If you made changes to the Community Services settings, click Update and restart the Sametime server for the changes to take effect.

Sure this is pretty much straight out of the Lotus Sametime Info Center, but it isn't the easiest thing to find and solve if you don't know what you are looking for and how the client behaves by default.