I want to host a Forge Server (probably 1.7.10, but maybe 1.10.2, I don't know if that changes anything). I have McAfee Total Protection (I won't be uninstalling it). And I also have Windows Defender (which is mostly kept disabled, but I know it is not completely disabled, and I will have to deal with it before this is over).
My Internet Provider allocates me a dynamic IP every time my modem gets turned off and on again, and that's not something you guys need to take into account. The server is just for friends and we're practically within shout range from one another.
My Network is like this: A modem connected to the outside (it is one of those "routed modems, which has more than just one outlet, so I don't know if that complicate things. We just use it like a normal modem: we connect one outlet to the one input of our router number 1). This modem is connected to a router. My PC and a bunch of other stuff, including another PC is connected to this router. Another router is connected to the first router and acts as a "repeater" just so the rest of the stuff can fit into the network. The first router also emits the WiFi signal (the modem's and the second router's WiFi signals are disabled)
What I want to know is how do I let my friends PCs get inside my network through Minecraft's port?
I didn't find the right solution from the Internet.