From the wikipedia page on RADIUS:
RADIUS is a client/server protocol that runs in the application layer,
using UDP as transport. The Remote Access Server, the Virtual Private
Network server, the Network switch with port-based authentication, and
the Network Access Server (NAS), are all gateways that control access
to the network, and all have a RADIUS client component that
communicates with the RADIUS server.
Could someone tell me how many actual piece of hardware I would need on the client side if I wanted to offer public wifi? Do these components listed above come built into a router, or a firewall, or a switch etc? Or would I need some servers on the client side? I was hoping to only have an access point and then a gateway to the internet… and on the other side my RADIUS server, web server (containing captive portal webpage etc)?
In a wifi deployment scenario your RADIUS client would be the access point. You’re looking for an AP that supports RADIUS.
In a wired Ethernet network the switch is the client, but you can’t just use the switch behind the access point as the RADIUS client in a wifi network if you want to use wifi to control the ability of clients to associate with the access point.
Typically you’d use a protocol like 802.1X to force clients to authenticate while associating with the wifi access point. This isn’t typically done in a public wifi access point where you want clients to associate w/o authentication.