Skype - random connections? Also takes ages to answer?

Whenever I have Skype running, my firewall is almost constantly telling
me that, for example

Someone from 88.135.80.125, port 44332 wants to send UDP datagram to
port 47964 owned by 'Skype' on your computer

Someone from wireless-165-124-119-184.nuwlan.northwestern.edu
[165.124.119.184], port 17258 wants to send UDP datagram to port 47964
owned by 'Skype' on your computer

etc.; i. e. the originating source varies at random, sometimes with a.

These stop if I stop Skype, so it is clearly to do with Skype. However,
nothing shows up within Skype if I permit them - no contact requests
etc. - so what are they about?

I have heard it alleged that Skype use spare capacity on your computer -
is that what this is about? (Definite answers only please!) If so, why
does it come in bursts with long gaps between?

It doesn't seem to affect the operation of Skype that I have them
blocked (or rather brought to my attention). I do have a couple of
allows - UDP out and TCP out - in my firewall for Skype.

Also, when someone calls me on Skype, I click Answer - but have to do so
(keep clicking) for ages: the ringing sound continues, and the Answer
button doesn't disappear, for many tens of seconds. The other person and
I can hear each other after about the first click.
--
J. P. Gilliver. UMRA: 1960/1985 MB++G.5AL-IS-P--Ch++(p)[email protected]+Sh0!:`)DNAf

Being punctual makes people think you have nothing to do.