im trying to set up a ftp server. i have it all set up except for my modem. my modem is connected to my linux computer and my windows computer is connected to linux. the ip address of linux is 192.168.1.2 and the address of windows is 192.168.0.5. my modem is a Netcomm NB1 and i went into the port forward part and i noticed that when i forward port 21 to linux and do a security check it says port 21 is open but when i forward it to windows it still says its closed and im not sure why.

It doesn't work because there is no direct connection between the modem and the Windows computer.

You should either connect the Windows machine directly to the "modem" (your modem seems to include a router device) or set up another port forwarding rule on the Linux computer.