I guess you won't have problems to make it work.
1 - First Step is to check your Soulseek settings, I suggest you to configure like in the image below. You can set the "Listening Port" to whatever between 50000/60000 to avoid any issues.
2 - Second Step is to adjust Windows settings.
- Check your network profile
° Open Windows settings.
° In the left menu, select Network and Internet.
° Select your active network (Wireless or Ethernet).
° In the profile type, select Private Network.
- Check your Windows Firewall Advanced Settings
° Hit Windows key + R to open and run a command.
° Type "wf.msc"
° In the left menu, Inbound Rules, check for 2 soulseek Rules (One for TCP ports and another for UDP).
° Double click in the rule, then go to "Advanced" tab, select just the Private profile.
° Click in the OK button to save and close the window.
!(you need to do it for both soulseek rules)!
3 - Third Step is to configure your Modem.
° Open Windows settings.
° In the left menu, select Network and Internet.
° Select your active network (Wireless or Ethernet).
° Find out your Default Gateway IP.
° Type the Gateway IP in your browse and log with admin privileges account.
Now pay attention, you can do it in two different ways. I don't have the exactly step by step for your modem here but I will speak generally, so you can figure out by yourself there.
This will make your setup stable and avoid any interruptions.
A) - You can go to the Home Network option in the upper menu and click in the Subnet and DHCP settings.
° You going to set your DHCP IP distribution to start a bit far (Ex: starting at 192.168.1.50 to 192.168.1.254)
° Set your Windows IP to manual and use something like:
IP: 192.168.1.40
Subnet Mask: 255.255.255.0
Gateway: 192.168.1.1 (your default gateway)
DNS: 192.168.1.1 (your default gateway)
B) - You can reserve the IP of your SoulSeek Machine.
Find an option to bind your Soulseek machine to a single IP. Normally called DHCP reservation.
And finally, use this Youtube Tutorial to configure the port forward in your modem using the IP of the SoulSeek Machine and the ports you set in the first step. Don't forget to configure both ports to TCP and UDP.
https://www.youtube.com/watch?v=iHFxa460VgIIt was a bit long procedure, but it is very solid. Once you do, just forget about it.
OBS: Soulseek server has being unstable lately, if you open the ports correctly, you will be able to test it, but maybe you can't login to search music :(
Hope you get it work.