[all variants] How to coect to another Ubuntu machine that using the same router but LAN to WLAN

Thread moved to Networking & Wireless.

Welcome. You are really asking two questions here: how to run a remote machine and how to share files/folders between two machines. Perhaps tackle getting a coection up and sharing files first then post remote machine setup questions in a new thread.

First off, can one machine ping the other and the router?

... where '***' matches the details of the final number of the router or the other machine. Hit enter. Getting a ping time?

I find it makes things easier if you set static IPs on the two machines so they don't change anytime.