def execute(self):
# Read packets and process
while True:
message, client_addr = self.server_socket.recvfrom(5000)
packet = struct.unpack('IHH' + str(len(message) - 8) + 's', message)
# Drop packet
if random.random() <= self.packet_drop_probability:
self.logger.info('Sequence Number %d - Packet Dropped', packet[0])
continue
self.logger.info('Sequence Number %d - Packet Received', packet[0])
# Verify packet checksum
if not Checksum.verify(message):
self.logger.info('Sequence Number %d - Packet is Corrupt', packet[0])
continue
self.process(packet, client_addr)
def get_next_ack(self):
message = self.socket.recv(self.mss)
packet = struct.unpack('IHH', message)
# Drop ack based on probability
if random.random() <= self.packet_drop_probability:
self.logger.info(
'Acknowledgement Number %d - Acknowledgement Dropped',
packet[0])
return False
self.logger.info(
'Acknowledgement Number %d - Acknowledgement Received', packet[0])
# Packet corrupted, ignore
if not Checksum.verify(message):
self.logger.info(
'Acknowledgement Number %d - Acknowledgement Corrupted',
packet[0])
return False
return packet
def startListening(self):
while True:
try:
data, addr = self.serverSock.recvfrom(1024)
packet = Packet()
packet.deserializePacket(data)
# print('addr: ', addr)
if (self.simulatePacketLoss()):
print("Simulating packet loss for packet with seq no: ",
packet.seq_num)
continue
if (Checksum.verify(packet.data, packet.checksum)):
ack_num, discard = self.protocol.receive_packet(packet)
if (discard):
print("Discarding packet with sequence number " +
str(packet.seq_num))
else:
print("Received Segment: ", str(packet.seq_num))
_ = self.serverSock.sendto(str(ack_num).encode(),
addr) #sending ack with ack_num
print("ACK Sent: ", str(ack_num))
else:
print(
"Discarding packet with invalid checksum, packet no: ",
packet.seq_num)
except KeyboardInterrupt:
print('Interrupted')
os._exit(0)
except ConnectionResetError:
pass # Do nothing.
except Exception:
raise Exception
return
