trouble getting RankCapes started

[RexyMex]

Hi,
i'd love to get this plugin/mod running but have several problems. Sorry for my newbie questions in advance - i have RankCapes-bukkit-1.7.2-2.0.0.26.jar plugin installed on my spigot mc server. I configured a port in the config file and added it to my firewall / router config.

config.yml:
cape-pack: capes.zip
port: 25568

server console log
19:37:47 RankCapes: Enabling RankCapes v2.0.0.26
19:37:47 RankCapes: Loading cape pack: capes.zip

Some questions concerning the port configuration:

1. Does the port require TCP or UDP (or both) protocols?
2. When i do 'telnet localhost 25568' on the windows command line, i don't get a connection. Is this intended behaviour?

On the client side i have RankCapes-client-forge-1.7.2-2.0.0.32.jar installed on Forge 1.7.10 / mc release 1.8.8. As admin i given myself rankcapes.cape.use.* via PermissionsEX plugin. When i press F5 to change view and 'c' to change a cape nothing happens (no cape shown, no menu pops up).

So some more questions here:
3) Do Rankcape server plugin and client mod versions have to match?
4) Is Forge version 1.7.10 ok for plugin forge version 1.7.2?

When i enter 'mycape', i get 'You have no cape. An internal error occurred while attempting to perform this command'.

5. What's going wrong here?

thanks!