"Ports" are completely arbitrary. You can use any one you want as long as nobody else is already listening on it.
In Sickbeard, if you go into Config then "Search Settings".
SABnzbd URL:
http://<bla address>:
8000/
The bold number has to match what you set in Newsbin. So, set Newsbin to 8100 and restart it. Then change the Sab URL to 8100 too. Use whatever address you already have in there. Only the port changes.
SABnzbd URL:
http://<bla address>:
8100/
After I restarted Newsbin this was what I see. Newsbin is listening on 8100.
PS C:\Windows\system32> netstat -ntb
Active Connections
Proto Local Address Foreign Address State
TCP 192.168.10.153:8100 192.168.10.201:61531 TIME_WAIT
TCP 192.168.10.153:8100 192.168.10.201:61532 TIME_WAIT
TCP 192.168.10.153:8100 192.168.10.201:61533 ESTABLISHED
[NewsbinPro.exe]
PS C:\Windows\system32>
You have to run a command prompt "As Administrator" to run this command.
I'd disable "Remote Control" while testing this.