Port Fowarding

It depends on the ports but in all cases it DOES expose you to danger.

How do you really know if there is or is not a bug in your software that someone may attack your machine on. Then after getting control of your machine they now can attempt to attack all the other machines in your house since now ALL ports are available to them to attempt to exploit.

And don't think nobody will find your machine. There are machines constantly sending traffic looking for holes.

If your router has a firewall then maybe you can convince him a safer configuration is possible. You would port forward the ports like normal but you would then put in firewall rules that say only accept connection from a small list of IP addresses. You can make the argument nobody would get control of the handful of big companies gaming servers to attack your house with.

If you need random other people IP to get access then I would say you are out of luck. It is HIM taking all the risk you are taking none and since it causes him no problems other than your complaining what does he get in return for taking even a small risk.

If I want it to be 'safe' the router should have a firewall? Where can I check that, we have a D-Link DIR-645 Router... Should only my IP be allowed or the IP of the game server?

Just a quick look at the manual appears it has a fairly advanced method of port forwarding that does have firewall features. You would want to create a inbound filter for each forwarded port.

It is the IP address of the game servers on the internet you need to add to this list.

Enable UPnP (universal plug-n-play) in the router in order for applications to automatically open/forward ports it needs. Those ports will close when you quit the application.