How to connect my computer to a server that is outside of its lan

[hnijhar]

k so. currently i have my server computer in room a, and i have 2 computers in room b. my current setup is.
Server------ethernet cable--------router-----modem, for the computers in room b, the setup is.......computers-------ethernet router----ethernet wire--------router------modem.

if i remove the switch in room b, then the computer in room b can communicate with the server computer, if i keep the ethernet router then i cant connect to my server. i need help. i need the computers in room b to be wired but there is only 1 wire in the room, so that is y i added the ethernet router. how can i get the server to connect to the computers in room b with the ethernet router?

My main wifi router is a Asus N66U
My ethernet router is a dlink dir 130

 

[RealBeast]

Put all of your devices on a single network (i.e. a single network address range that uses only one DHCP server, for example gateway address 192.168.0.1 and all the devices will be 192.168.0.2 to .254). Turn off all the router functions of your "Ethernet router" to make it act as a switch and the machines should connect fine. If you also need wireless just configure it as an access point.