I would like to connect a Raspberry Pi 4B (RPI) to a PC via Ethernet using TCPIP. Both devices should have fixed IPv4 address. PC is the server, Raspberry is the client. Server program is running under Windows 7 (on a Dell laptop) or Windows 10 (on an Acer laptop). Server IPv4 is 10.0.9.2, Raspberry IPv4 address is 10.0.9.9
The Dell-RPI connection is working, but when the RPI is connected to the Acer no SYN/ACK is sent for the SYN package. After a couple of retransmissions, the Raspberry application quits with "Connection timed out" error. Packages are monitored by Wireshark on the server side.