Hi Alastair!

I’ve checked your code once again and I found an error, in line:

ack_list.remove(scapy[scapy.TCP].seq)

You are missing the proper name of the packet which is scapy_packet, so it should be like:

ack_list.remove(scapy_packet[scapy.TCP].seq)

Change it and let me know how it goes!
Diego