Why is µTorrent's web UI slow to start?

Question

I have a wireless home network with one desktop connected to the router via cable and a laptop connected via wireless. I have a uTorrent client on the desktop, setup with its web UI.

When I try to access it from the laptop, the response time until anything starts moving on the UI is huge. Once the UI comes up, it is rather responsive. Why does it take forever to start?

Answer 1

When you first load the page, the browser has to load all the resources (HTML, Javascript and images).

No javascript (used heavily for the web UI) can run until the page is fully loaded, thus the initial delay.

Once the initial load is done, all the updates are done via AJAX (well, JSON, not XML), so will feel snappier (no full page reload required, it's only a few kilobytes of data which is used to update the page)

Can it be that the heavy upload cause by uTorrent blocks the upload from the web UI?

This is unlikely if it's slow over your local wireless network - it should be able to transfer about 1-5 megabyte/s, unless you can upload at that speed it's unlikely to cause noticeable slowdown. Over the internet, yes, too high upload speeds (saturating your upload) will cause everything to slow down a lot (as Slink84 says, you should limit uTorrent's upload speed to about 20kilobytes/s under your max upload speed)

Does it happen even when no torrents are running?

Have you tried connecting to the machine in other ways - such as the Windows file sharing, or something like XAMMP (a web server) - if these are similarly effected, it's not uTorrents fault, but some other factor (the router, perhaps?)

Another thing to try is telnet [uTorrent machines IP] [web interface port] then enter GET / followed by return twice - this is basically what the browser does, just without anything fancy like images, CSS or javascript. If you see a lot of HTML instantly, it may be something weird with your browser..