receiver.py

from random import Random
import socket
from threading import *


def makeseg(contents, seq_seg, seq_ack, is_ack):
    return "data = " + str(contents) + " seqSeg = " + str(seq_seg) + " seqAck = " + str(seq_ack) + " isack = " + str(is_ack)


serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
host = "127.0.0.1"
port = 8000
serversocket.bind((host, port))

seq_seg = 0
seq_ack = 1

seed = input("Choose a seed: ")

prob = float(input(
    "What is the probability that the data segment 1 or 2 has been corrupted? (between 0 inclusive and 1 exclusive) "))

rand = Random()
rand.seed(seed)

serversocket.listen(5)
c, addr = serversocket.accept()

last = ""

while True:
    num = rand.random()
    received = c.recv(4096).decode()
    if received != "":
        print("")
        if num >= prob:
            # Not corrupted
            print("Segment received contains: " + received)

            print("An ACK" + str(seq_ack) + " is about to be sent")

            if "seqSeg = 0" in received:
                seq_seg = 0
                seq_ack = 0
            elif "seqSeg = 1" in received:
                seq_seg = 1
                seq_ack = 1

            ack = makeseg(0, seq_seg, seq_ack, 1)

            if last == received:
                print("The receiver is moving back to state WAIT FOR " +
                      str(seq_ack) + " FROM BELOW")
            else:
                print("The receiver is moving to state WAIT FOR " +
                      str(seq_ack) + " FROM BELOW")

            print("ACK to send contains: " + ack)
            c.send(ack.encode())
        else:
            # Corrupted
            print("A Corrupted segment has been received")
        last = received

c.close()

sender.py

from random import Random
import socket
from threading import *
import time


def makeseg(contents, seq_seg, seq_ack, is_ack):
    return "data = " + str(contents) + " seqSeg = " + str(seq_seg) + " seqAck = " + str(seq_ack) + " isack = " + str(is_ack)


serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
host = "127.0.0.1"
port = 8000
serversocket.connect((host, port))

seq_seg = 0
seq_ack = 0

seed_timing = input("Choose a seed for timing: ")
num_segments = int(input("What is the number of segments to send? "))
seed_corrupted = input(
    "Choose a seed for checking if an ACK has been corrupted: ")
prob = float(input(
    "What is the probability that an ACK has been corrupted? (between 0 inclusive and 1 exclusive) "))
seed_data = input("What is the seed for the packet data? ")
travel_time = input("What is the round trip travel time? ")

timing_gen = Random()
timing_gen.seed(seed_timing)

rand_corrupted_gen = Random()
rand_corrupted_gen.seed(seed_corrupted)

data_gen = Random()
data_gen.seed(seed_data)

serversocket.settimeout(3.0)

data = int(data_gen.random() * 1024)
resend = 0
segments = 0

while segments <= num_segments:
    print("")

    rand_corrupted = rand_corrupted_gen.random()

    if resend:
        print("A data segment with sequence number " +
              str(seq_seg) + " is about to be resent ")
    else:
        print("A data segment with sequence number " +
              str(seq_seg) + " is about to be sent ")

    seg = makeseg(data, seq_seg, seq_ack, 0)

    serversocket.send(seg.encode())

    if resend:
        if seq_seg == 0:
            print("The sender is moving back to state WAIT FOR ACK 0")
        elif seq_seg == 1:
            print("The sender is moving back to state WAIT FOR ACK 1")
    else:
        if seq_seg == 0:
            print("The sender is moving to state WAIT FOR ACK 0")
        elif seq_seg == 1:
            print("The sender is moving to state WAIT FOR ACK 1")

    print("Segment sent: " + seg)

    try:
        response = serversocket.recv(4096).decode()
    except socket.timeout:  # fail after 1 second of no activity
        resend = 1
        continue

    data = int(data_gen.random() * 1024)
    resend = 0
    segments += 1

    if seq_seg == 0:
        seq_seg = 1
    elif seq_seg == 1:
        seq_seg = 0

    if rand_corrupted >= prob:
        # not corrupted
        if "seqAck = 0" in response:
            print("An ACK0 segment has just been received")
            print("The sender is moving to state WAIT FOR CALL 1 FROM ABOVE")
        elif "seqAck = 1" in response:
            print("An ACK1 segment has just been received")
            print("The sender is moving to state WAIT FOR CALL 0 FROM ABOVE")
        else:
            print("Error: can't read response")
    else:
        # corrupted
        print("A Corrupted ACK segment has just been received")

    time.sleep(int(timing_gen.random() * 5))

serversocket.shutdown(socket.SHUT_RDWR)
serversocket.close()