Yes this is exactly the same problem. Maybe you can get some support from your ISP or your modem manufacturer.

is the firewall on your router on? i have the option to turn on/off my router's firewall. you should look into that...

I've forwareded the right ports in my router and also tried connecting directly without the router. So my guess is that the modem is the problem.

@Dark_samurai
Ye, good idea tomorrow I'll phone my ISP, it's to late now, maybe they know something. For now, hopefully google knows

access the router(if you know how) and see if your router firewall is on

I've accessed my router and turned of my firewall and no changes but I found a manual on the internet to open the ports in my modem. Maybe ( hopefully ) that helps. If I remember correct I've already tried that but I'm not sure.

www.portforward.com you can find manuals for PF for every router

Thanks Croman, I forward the ports in my router, but it didn't work. Even when I connect my PC directly on my modem, turn off the firewall inside my modem and turn off the windows firewall. Still no succes.. Tomorrow I'll phone my ISP and if they dont have any answers, then I'm out of ideas

hey DarkSamurai, but why it gives him an error "Malfunction W1527 Lost connection to server". that should mean that he did connect to the server but he lost connection. if his friend cant connect shouldnt it be something like cant connect or cant find the server error message?

To connect through the internet to your own IP usually fails, this is why the localhost connection (127.0.0.1) is a better option.

If you are having more than one PC, and can reacht the other PC over the LAN, there is another thing.
In your router you must not just forward the port, but also direct traffic from and to the IP of the server PC, otherwise the data gets scattered in your LAN.
Change the IP of the server PC to static, and then do not just forward the port but forward it with the internal IP of the server PC.
This way the incoming data gets directed to the server and connection should be possible.

If you have just one PC, either ask a friend to connect or rent a external server.

The disconnect event is also called if he tries to connect and fails.