Packet-Switching-Example/packetswitchingmultir.py at main · timcarpe/Packet-Switching-Example · GitHub

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import random
import time

senderPackets = []
receiverPackets = []
r1 = []
r2 = []
r3 = []
r4 = []
message = ""
parity = 0

#input a message to send
message = input("Input a message: ")

#Go through each character of the message and turn it into a packet [header,payload,trailer]
#In each packet we will record the packet number which is the current list length, the character as payload, and the parity 'bit' which is the current length modulus 2 which alternates 0 or 1
for char in message:
    #[packet number, payload, parity check]
    senderPackets.append([len(senderPackets), char, len(senderPackets)%2])

print("Packets to be sent:", senderPackets)

loopCount = 0

while bool(senderPackets + r1 + r2 + r3 + r4):
#send each packet in the senderPackets list

    if len(senderPackets) > 0:
        #get and remove the first packet from the list
        nextPacket = senderPackets.pop(0)
        #choose a random router to send to
        router = random.choice([r1,r2])
        #add packet to the router list
        print("Packet number", nextPacket[0], "with payload", nextPacket[1], "sent")
        router.append(nextPacket)

    if len(r1) > 0:
        randomPacket = random.choice(r1)
        #choose a random router to send to
        router = random.choice([r2,r3,r4])
        #add packet to the router list
        print("Packet number", randomPacket[0], "with payload", randomPacket[1], "sent")
        router.append(randomPacket)
        r1.remove(randomPacket)

    if len(r2) > 0:
        randomPacket = random.choice(r2)
        #choose a random router to send to
        router = random.choice([r1,r3,r4 ])
        #add packet to the router list
        print("Packet number", randomPacket[0], "with payload", randomPacket[1], "sent")
        router.append(randomPacket)
        r2.remove(randomPacket)

    if len(r3) > 0:
        randomPacket = random.choice(r3)
        #choose a random router to send to
        router = random.choice([r2,r4,receiverPackets])
        #add packet to the router list
        print("Packet number", randomPacket[0], "with payload", randomPacket[1], "sent")
        router.append(randomPacket)
        r3.remove(randomPacket)

    if len(r4) > 0:
        randomPacket = random.choice(r4)
        #choose a random router to send to
        router = random.choice([r2,r3,receiverPackets])
        #add packet to the router list
        print("Packet number", randomPacket[0], "with payload", randomPacket[1], "sent")
        router.append(randomPacket)
        r4.remove(randomPacket)

    loopCount += 1
    time.sleep((0.1))
    print("----\nFinished loop", loopCount, ":" , "\nSender:", senderPackets, "\nR1:", r1, "\nR2:", r2, "\nR3:", r3, "\nR4:", r4)


#output unsorted packets at receiver for checking
print("Unsorted packets received at receiver:")
for packet in receiverPackets:
    print(packet)

#this returns the packet number so we can sort
def packetNumber(e):
    return e[0]

#sort the packets by the packet number
receiverPackets.sort(key=packetNumber)

receiverMessage = ""
parity = 0

#reconstruct the message and also check for parity in message (should alternate between 1 and 0)
for packet in receiverPackets:
    if parity % 2 == packet[2]:
        print("Parity check for packet passed!")
    parity += 1
    receiverMessage += packet[1]
    time.sleep(0.05)

print("------------")
print("Message received after", loopCount, "iterations :", receiverMessage)