I see the issue both on the same computer, so loopback, as well as on two computers on the same LAN. I tested with unidirectional traffic. Pretty easy to test f

I see the issue both on the same computer, so loopback, as well as on two computers on the same LAN. I tested with unidirectional traffic. Pretty easy to test for yourself. The problem appears to be with the TCP protocol implementation. For UDP transmission speed is the same both ways.