OUCH!
https://www.itfast.com.au/shopnow.asp?ID=EPL-14U
I found what appears to be a similar device - expensive, and that's only one.
The best way to split your interneat connection, is with a suitable router..
An ADSL router has the ADSL modem built in, and is used instead of the supplied modem - settings need to be noted and applied to it.
A cable router is used with a cable modem with an ethernet port, and may also be used with an ADSL modem if that has an ethernet port - most supplied ones are cheap USB only.
A wired router generally has 4 ethernet ports, while a "wireless" router normally has at least one wired port available, in addition to wireless.
The router solution is infinitely preferable to relying on one PC acting as the server, but you can set up ICS (Internet Connection Sharing) on a computer using an ethernet port/card (a second one, if the internet connection is also by ethernet instead of USB), WiFi point to point (a wireless card or USB pod on each PC), or even Bluetooth point to point, though the low security of bluetooth makes this a risky option.