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How to use next_sequence_number method in localstack

Best Python code snippet using localstack_python

gbn.py

Source:gbn.py

1import config2import threading3import time4import udt5import util6# Go-Back-N reliable transport protocol.7class GoBackN:8    NO_PREV_ACK_MSG = (9        "Don't have previous ACK to send, will wait for server to timeout."10    )11    # "msg_handler" is used to deliver messages to application layer12    def __init__(self, local_port, remote_port, msg_handler):13        util.log("Starting up `Go Back N` protocol ... ")14        self.network_layer = udt.NetworkLayer(local_port, remote_port, self)15        self.msg_handler = msg_handler16        self.sender_base = 017        self.next_sequence_number = 018        self.set_timer()19        self.window = [b""] * config.WINDOW_SIZE20        self.expected_sequence_number = 021        self.receiver_last_ack = b""22        self.is_receiver = True23        self.sender_lock = threading.Lock()24    def set_timer(self):25        self.timer = threading.Timer((config.TIMEOUT_MSEC / 1000.0), self._timeout)26    # "send" is called by application. Return true on success, false otherwise.27    def send(self, msg):28        self.is_receiver = False29        if self.next_sequence_number < (self.sender_base + config.WINDOW_SIZE):30            threading.Thread(target=self._send_helper(msg))31            return True32        else:33            util.log("Window is full. App data rejected.")34            time.sleep(1)35            return False36    # Helper fn for thread to send the next packet37    def _send_helper(self, msg):38        self.sender_lock.acquire()39        packet = util.make_packet(msg, config.MSG_TYPE_DATA, self.next_sequence_number)40        packet_data = util.extract_data(packet)41        self.window[self.next_sequence_number % config.WINDOW_SIZE] = packet42        util.log("Sending data: " + util.pkt_to_string(packet_data))43        self.network_layer.send(packet)44        if self.sender_base == self.next_sequence_number:45            if self.timer.is_alive():46                self.timer.cancel()47            self.set_timer()48            self.timer.start()49        self.next_sequence_number += 150        self.sender_lock.release()51        return52    # "handler" to be called by network layer when packet is ready.53    def handle_arrival_msg(self):54        msg = self.network_layer.recv()55        msg_data = util.extract_data(msg)56        if msg_data.is_corrupt:57            if self.is_receiver:58                if self.expected_sequence_number == 0:59                    util.log("Packet received is corrupted. " + self.NO_PREV_ACK_MSG)60                    return61                self.network_layer.send(self.receiver_last_ack)62                util.log(63                    "Received corrupted data. Resending ACK: "64                    + util.pkt_to_string(util.extract_data(self.receiver_last_ack))65                )66            return67        # If ACK message, assume its for sender68        if msg_data.msg_type == config.MSG_TYPE_ACK:69            self.sender_lock.acquire()70            self.sender_base = msg_data.seq_num + 171            if self.sender_base == self.next_sequence_number:72                util.log(73                    "Received ACK with seq # matching the end of the window: "74                    + util.pkt_to_string(msg_data)75                    + ". Cancelling timer."76                )77                self.timer.cancel()78            else:79                util.log(80                    "Received ACK: "81                    + util.pkt_to_string(msg_data)82                    + ". There are messages in-flight. Restarting the timer."83                )84                if self.timer.is_alive():85                    self.timer.cancel()86                self.set_timer()87                self.timer.start()88            self.sender_lock.release()89        # If DATA message, assume its for receiver90        else:91            assert msg_data.msg_type == config.MSG_TYPE_DATA92            util.log("Received DATA: " + util.pkt_to_string(msg_data))93            if msg_data.seq_num == self.expected_sequence_number:94                self.msg_handler(msg_data.payload)95                ack_pkt = util.make_packet(96                    b"", config.MSG_TYPE_ACK, self.expected_sequence_number97                )98                self.network_layer.send(ack_pkt)99                self.receiver_last_ack = ack_pkt100                self.expected_sequence_number += 1101                util.log("Sent ACK: " + util.pkt_to_string(util.extract_data(ack_pkt)))102            else:103                if self.expected_sequence_number == 0:104                    util.log("Packet received is out of order. " + self.NO_PREV_ACK_MSG)105                    return106                util.log(107                    "DATA message had unexpected sequence #"108                    + str(int(msg_data.seq_num))109                    + ". Resending ACK message with sequence # "110                    + str(int(self.expected_sequence_number - 1))111                    + "."112                )113                self.network_layer.send(self.receiver_last_ack)114        return115    # Cleanup resources.116    def shutdown(self):117        if not self.is_receiver:118            self._wait_for_last_ACK()119        if self.timer.is_alive():120            self.timer.cancel()121        util.log("Connection shutting down...")122        self.network_layer.shutdown()123    def _wait_for_last_ACK(self):124        while self.sender_base <= self.next_sequence_number - 1:125            util.log(126                "Waiting for last ACK from receiver with sequence # "127                + str(int(self.next_sequence_number - 1))128                + "."129            )130            time.sleep(1)131    def _timeout(self):132        util.log(133            "Timeout! Resending all packets in window. Resending packets with seq #s "134            + str(self.sender_base)135            + "-"136            + str(self.next_sequence_number - 1)137            + "."138        )139        self.sender_lock.acquire()140        if self.timer.is_alive():141            self.timer.cancel()142        self.set_timer()143        for i in range(self.sender_base, self.next_sequence_number):144            pkt = self.window[(i % config.WINDOW_SIZE)]145            self.network_layer.send(pkt)146            util.log("Resending packet: " + util.pkt_to_string(util.extract_data(pkt)))147        self.timer.start()148        self.sender_lock.release()...

receptor.py

Source:receptor.py

1import socket2import numpy as np  # pip install numpy34socketUDP = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)5transmissor = ("127.0.0.1", 2020)6receptor = ("127.0.0.1", 3030)7socketUDP.bind(receptor)8buff_size = 10000910next_sequence_number = 01112def verify_checksum(data):13    data_sum = np.uint16(0)14    for element in data:15        data_sum += element16    return data_sum == 0xFFFF1718def calculate_checksum(data):19    data_sum = np.uint16(0)20    for element in data:21        data_sum += element22    return np.invert(data_sum)2324def udt_send(packet):25    socketUDP.sendto(packet.tobytes(), transmissor)2627def rdt_rcv():28    while True:29        message, source = socketUDP.recvfrom(buff_size)30        if source == transmissor:31            return np.frombuffer(message, dtype=np.uint16)3233def make_pkt(Is_ACK,seq_num):34    sndpkt = np.array([], np.uint16)35    sndpkt = np.append(sndpkt, np.uint16(seq_num))36    sndpkt = np.append(sndpkt, np.uint16(0))  # checksum37    sndpkt = np.append(sndpkt, np.uint16(Is_ACK))  # is_ack3839    sndpkt[1] = calculate_checksum(sndpkt)40    return sndpkt4142if __name__ == "__main__":43    44    while True:45        sndpkt = []46        print("Waiting for Data...")47        rcvpkt = rdt_rcv()48        49        notcorrupt = verify_checksum(rcvpkt)50        haseq = rcvpkt[0] == next_sequence_number51        # print(f'Dados recebidos {rcvpkt}') 52        print("NÃ£o EstÃ¡ Corrompido?",notcorrupt)  53        print("Tem seq?",haseq)  54        if haseq:55            if notcorrupt:56                sndpkt = make_pkt(1,next_sequence_number)57                if next_sequence_number == 0:58                    next_sequence_number = 159                else:60                    next_sequence_number = 061                print(f'Dados recebidos {rcvpkt}')        62            else:63                sndpkt = make_pkt(0,next_sequence_number)64        if len(sndpkt) > 0:65            print("Dados Enviados ",sndpkt)66            udt_send(sndpkt)67686970
...

transmissor.py

Source:transmissor.py

1import socket2import numpy as np  # pip install numpy345socketUDP = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)6transmissor = ("127.0.0.1", 2020)7receptor = ("127.0.0.1", 3030)8socketUDP.bind(transmissor)9buff_size = 100001011next_sequence_number = 0121314def calculate_checksum(data):15    data_sum = np.uint16(0)16    for element in data:17        data_sum += element18    return np.invert(data_sum)192021def verify_checksum(data):22    data_sum = np.uint16(0)23    for element in data:24        data_sum += element25    return data_sum == 0xFFFF262728def udt_send(packet):29    socketUDP.sendto(packet.tobytes(), receptor)303132def rdt_rcv():33    while True:34        message, source = socketUDP.recvfrom(buff_size)35        if source == receptor:36            return np.frombuffer(message, dtype=np.uint16)373839def rdt_send(data):40    global next_sequence_number4142    sndpkt = np.array([], np.uint16)43    sndpkt = np.append(sndpkt, np.uint16(next_sequence_number))44    sndpkt = np.append(sndpkt, np.uint16(0))  # checksum45    sndpkt = np.concatenate((sndpkt, data))4647    sndpkt[1] = calculate_checksum(sndpkt)48    udt_send(sndpkt)4950    while True:51        rcvpkt = rdt_rcv()52        is_corrupt = not verify_checksum(rcvpkt)53        is_ack = rcvpkt[2] == True54        is_nack = rcvpkt[2] == False55        print("Dados recebidos ", rcvpkt)56        print("EstÃ¡ corrompido? ", is_corrupt)57        print("EstÃ¡ Nack? ", is_nack)58        print("EstÃ¡ Ack? ", is_ack)59        print("Seq Num? ", next_sequence_number)60        61        if is_corrupt or is_nack:62            udt_send(sndpkt)63        if is_ack and not is_corrupt:64            break6566    if next_sequence_number == 0:67        next_sequence_number = 168    else:69        next_sequence_number = 0707172if __name__ == "__main__":73    i = 174    while i <= 3:75        dados = np.random.randint(5, size=10, dtype=np.uint16)76        print(f'Dados a serem enviados {dados}')77        rdt_send(dados)
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