On Sun, Jan 2, 2011 at 9:47 AM, <<a href="mailto:lziegler@unix.csbsju.edu">lziegler@unix.csbsju.edu</a>> wrote: <div class="gmail_quote"><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"> It is clear that it is not MY firewall that is the problem since Transmission worked very well in both directions until the last 3 weeks or so. I suspect my ISP is simply blocking ports but I am not sure how to check this. </blockquote></div> For diagnostics, I'd still suggest temporarily turning off your firewall during testing. Do a net search for 'port scan' and you will find a number of online tools that can scan your ports. Set BT to a scanable port and see what happens. With my ISP, they are throttling my upload when I'm downloading. So I have to set my upload limit to 10 Kbps during downloads; I can open up my upload speed after the download is complete.