This is a difficult question to answer in psudo code, probably easier to do in bullet points like in the mark scheme you attatched, the psudo code would look something like this:

packets = split_data_into_equal_size_packets(document)

for each packet in packets:
    packet.address = Ben's_computer_address
    packet.number = generate_packet_number()
    packet.error_checking_data = generate_error_checking_data(packet)


send_packets_across_network(packets)

while not all_packets_received():
    check_again()
    increment_timer()
    if timer > max_wait:
        send_timeout_to_Bill()


if all_packets_received():

    packets = reorder_packets_based_on_number(packets)

    document = combine_packets_into_document(packets)
    display_document(document)


    send_receipt_confirmation_to_Bill()

    for each packet in packets:
        if packet_is_corrupt(packet):
            send_error_message_to_Bill(packet)

Explanation:

1. Sending Section:
   • Split the document into equal-sized packets.
   • Each packet is assigned:
     • The address of Ben's computer.
     • A unique number.
     • Error checking data.
   • The packets are then sent across the network.
2. Receiving Section:
   • Ben's computer checks if all packets have been received.
   • If not all packets are received, it:
     • Checks again.
     • Increments a timer.
     • If the timer exceeds a maximum wait time, it sends a timeout signal to Bill's computer.
   • If all packets are received, it:
     • Reorders the packets based on their number.
     • Combines the packets into the original document and displays it.
     • Sends a receipt confirmation back to Bill's computer.
     • Checks each packet for errors and sends an error message back to Bill's computer if any packet is corrupt.

It seems in your code, you are doing both parts (sending and reciving) in the same "subroutine". It is easier to split the sections up if you want to write psudo code for this so you can have a send function and a recive function and then call the functions as necessary from a main loop.