Wait, you do a trick that is not official but works very very well.
you have this:
Machine 1 - cable 1 - active network port 1
because your cable is passing from one place to other and you not want or can’t put a second cable you can do this:
machine 1 - adapter - cable 1 - adapter - active network port 1
machine 2 /… … … … … … … … … … \ active network port 2
where the adapters you use a female rj45 to split to other 2 males.
The trick is that tcp/ip in reality only use 4 wires, so the other 4 non used wires you can use to connect a second pc. the adapters what do is rewire in both sides to on the males sides use the correct pins and in the female side to use all 8 rj45 wires (4 wires pc1 and 4 wires pc2).
I can ensure that it works perfectly well even with cables + 100m and in Gbps.
What is important is you do the correct wiring. Search on the internet for this trick to see what pairs you should use and the scheme for the adapter home made.
Its a unofficial trick and works!