I got the same message, and after a little tinkering, found that Trio was (for some inexplicable reason) expecting receiver.arf to exist in the directory where you started the server...ie, if you started it from foo/trio/bin, then receiver.arf should be in foo/trio.bin. I started it in /usr/local/trio/bin, but receiver.arf was in /usr/local/trio. I copied it over and everything worked fine.

I'm currently looking into how to change this. First I have to figure out Trio's build system (looks like he uses ant) and then I'll look at hacking the code ;-)