As long at you are under 100metres , just run cables. Run the outdoor Cat6a variety, or lay regualr in conduit, Dont run just one, run two (One for now and one for later/if something breaks.)

You can buy other point to point wireless netwoking devices as suggested below, but these will all add more power use and complexity as they are a little specialised to get working well.

Cat6a will allow you many years of cheap and reliable service and will be cheper in the long run unless you've got some really difficult terrain to work with.

You could also run Multi Mode fibre optic cable up to 550m with 2 cheap swiches that have an SPF port at either end. This will cost a little more, but willgive you near unlimited expansion