I'm wondering if its possible to host a Minecraft server on my PC and have my wife connect to that server without any internet connection. We are willing to get a router/modem or switch if need be. We just can't use internet and need instructions on what to get, how to set it up, and how to use it. My hope is that it is possible to have our computers in the same room, plug our PCs into a router that has no internet service via Ethernet cables, turn on the server on my PC, my wife can type in the IP and we can play together.
Yes you can. I am running a Minecraft server on a separate Linux machine, and me and my brother connect to the Minecraft server from separate computers, all of it from our own wireless LAN and without an Internet connection.
We are using a WiFi router that is not connected to the Internet, the computer running the server is an old laptop, and then we have two additional computers, each running an instance of Minecraft, and it all works fine.
I'm not sure about using only a network switch, because you need to be connected at the IP layer, since you need to specify the internal, private IP address of the computer running the Minecraft server from the Minecraft client in order to join.
So in a nutshell, you will need to download and install the Minecraft server, install the latest Java OpenJDK, run the Minecraft server, read the eula, and last in order for this to work completely offline (that is, we want this to work without an Internet connection), you will need to go into the Minecraft server configuration file, locate the property of online-mode=true and set it to online-mode=false.
This setting basically controls whether or not players authenticate to Mojang's servers before they connect to your server, and it prevents players with cracked clients from connecting to your server, but since you will be hosting and joining from within an internal, private network anyways it does not matter. No one will be connecting to your server from the outside world if there is not a connection to the Internet anyway.
For more details about how to install and run a Minecraft server, there are many guides out there. It's actually pretty simple, if you're comfortable using a console screen and know just a little bit about IP addresses and editing a configuration file with a text editor. For me, I run the Mi ecraft server and I was able to connect to it with my brother and start playing right away, without having to mess around with the server at all.
So there you have it, I hope this helps someone.