I have been troubleshooting W5500. I have come across weird things.
When W5500 operates as server (socket status = 0x14) when it gets SYN packet it sends back RST/ACK instead of establishing connection.
when W5500 acts as a client, my PC does exactly the same.
sadly I cannot include pictures due to rules of this forum.
I also tried turning firewall off.
When WIznet chip sends or receives a RST packet instead of ACK, WIZChip port configuration of listening or connection is wrong.
You first check the port value is correct.
You can check easy by using wireshark packet caputer program.
As it turns out you were right! thanks for pointing out.
if everyone is wondering I had my server at 9999 but I wrote 99 and 99 in port registers of W5500 resulting in actual pirt bumber of 25443