"remote-test-server" on qemu-image with a tap interface throws an error.
The emulators for rust testing are with tcp port forwarding so used
slirp method with added rust port.
I'm not sure I understand - what kind of error? In both cases the server starts listening on a port, so in slirp scenario the address is
127.0.0.1:12345 (prone to breakage if something else on the build host took that port btw, including another instance of the same test), in tap it would be
192.168.7.2:12345. For the client you simply supply that via TEST_DEVICE_ADDR. No?