Right click on the search page's column header & make sure chat is ticked. This way, you'll be able to see which hosts have chat enabled (a smiley means they have chat enabled). Now, right click on a file where you see a & choose 'chat with host'. A chat box will open & you can try to chat with the host of that file!

You can do the same thing with the monitor page & see which uploaders have chat on.

Like I said before though, sometimes it won't work!!