def sendAck(self):
"""Function for building and sending acknowledgement frame"""
frame = Frame(self.senderAddress, self.receiverAddress,
self.frameType['ack'], self.seqNo,
'acknowledgement frame')
self.recentACK = frame
self.connection.send(str.encode(frame.toBinaryString(22)))
def sendAck(self):
"""Function for building and sending ACK frame"""
frame = Frame(self.senderAddress, self.receiverAddress,
self.frameType['ack'], self.front,
'acknowledgement frame')
self.recentACK = frame
print("Sent ACK", self.front)
self.connection.send(str.encode(frame.toBinaryString(22)))
self.lastACKsent = time.time()
def sendFrames(self):
"""Function to handle data sending"""
time.sleep(0.2)
# mark the start of sending
print("\n", self.name, " starts sending data to ", self.receiver, "\n")
# open data file for reading
file = open(self.fileName, 'r')
# read data from file
data_frame = file.read(46)
# loop until whole data is sent
while data_frame:
# if window is not full, send another frame
if (self.window_size < MAX_WINDOW_SIZE):
# build frame using data, type and sequence number
frame = Frame(self.senderAddress, self.receiverAddress,
self.frameType['data'], self.end, data_frame)
# store current frame for re-transmission (if needed)
self.current_window[self.end] = frame
# acquire window write lock
self.lock.acquire()
# send the frame
self.connection.send(str.encode(frame.toBinaryString(46)))
print("\nSTATUS: FRAME", self.end, "SENT TO CHANNEL")
self.frameTimer[self.end] = time.time()
# update end, window size and other parameters accordingly
self.end = ((self.end + 1) % MAX_SEQUENCE_NUMBER)
self.window_size += 1
self.frameCount += 1
self.totalFrameCount += 1
# read next data frame
data_frame = file.read(46)
# release window write lock
self.lock.release()
# if all data has been read, break
if len(data_frame) == 0: break
# set the end-transmitting flag True
self.eot = True
# close the data file
file.close()
def sendFrame(self):
"""Function to send data"""
time.sleep(0.2)
# open data file for reading
file = open(self.fileName, 'r')
# read the first data to be sent in a frame
data = file.read(46)
self.seqNo = 0
self.frameCount = 0
self.totalframeCount = 0
# loop until whole data is sent
while data:
if (not self.frameSent):
# build frame using data, type and sequence number
frame = Frame(self.senderAddress, self.receiverAddress,
self.frameType['data'], self.seqNo, data)
# store current frame for re-transmission (if needed)
self.lastFrame = frame
# acquire the send lock
self.lock.acquire()
# send the frame and start sent-timer
self.connection.send(str.encode(frame.toBinaryString(46)))
self.sentTime = time.time()
self.frameSent = True
# update sequence number and other parameters accordingly
self.seqNo = (self.seqNo + 1) % 2
self.frameCount += 1
self.totalframeCount += 1
print("\nSTATUS: FRAME", self.frameCount, "SENT TO CHANNEL")
# release the send lock
self.lock.release()
# read next data
data = file.read(46)
# if all data has been read, break
if len(data) == 0: break
# set the end of transmission flag to True
self.eot = True
# close the data file
file.close()
class Receiver:
def __init__(self, connection, name: str, senderAddress: int,
receiverAddress: int, file: str):
# get the client/receiver connection and other informations (name, data file name)
self.connection = connection
self.name = name
self.filename = file
self.senderAddress = senderAddress
self.receiverAddress = receiverAddress
# some transmission control variables and flags
self.frameType = {'data': 0, 'ack': 1}
self.seqNo = 0
self.recentACK = Frame(senderAddress, receiverAddress, 1, 0,
"Acknowledgement Frame")
def sendAck(self):
"""Function for building and sending acknowledgement frame"""
frame = Frame(self.senderAddress, self.receiverAddress,
self.frameType['ack'], self.seqNo,
'acknowledgement frame')
self.recentACK = frame
self.connection.send(str.encode(frame.toBinaryString(22)))
def resendPreviousACK(self):
"""Function for resending previous acknowledgement frame if needed"""
self.connection.send(str.encode(self.recentACK.toBinaryString(22)))
def startReceiving(self):
"""# Function for receiving data"""
time.sleep(0.4)
# receive data from sender
data = self.connection.recv(576).decode()
# initialise total data received
total_data = ""
while data != "end":
print("\nSTATUS: FRAME RECEIVED")
# build frame from binary data string
frame = Frame.build(data)
# If frame has no error
if not frame.hasError():
print("STATUS: NO ERROR FOUND")
seqNo = frame.getSeqNo()
if self.seqNo == seqNo:
# extract data
data = frame.getData()
# print(data)
total_data += data
# update the sequence number of ACK
self.seqNo = (self.seqNo + 1) % 2
# send the corresponding ACK
self.sendAck()
print("STATUS: ACK SENT\n")
# if sequence number is not what is required, resend the previous ACK
else:
self.resendPreviousACK()
print("STATUS: ACK RESENT")
# discard erroneous frame
else:
print("STATUS: FRAME DISCARDED")
# wait and receive next frame
data = self.connection.recv(576).decode()
file = open(self.filename, 'w')
file.write(total_data)
file.close()
def sendNak(self):
"""Function for building and sending NAK frame"""
frame = Frame(self.senderAddress, self.receiverAddress,
self.frameType['nak'], self.front, 'not acknowledgement')
self.connection.send(str.encode(frame.toBinaryString(22)))
print("Sent NAK", self.front)
class Receiver:
def __init__(self, connection, name: str, senderAddress: int,
receiverAddress: int, file: str):
# get the client/receiver connection and other informations (name, data file name)
self.connection = connection
self.name = name
self.filename = file
self.senderAddress = senderAddress
self.receiverAddress = receiverAddress
# some transmission control variables and flags
self.frameType = {'data': 0, 'ack': 1, 'nak': 2}
self.front = 0
self.end = WINDOW_SIZE
self.window = [0 for i in range(0, MAX_SEQUENCE_NUMBER)]
self.filled_up = [False for i in range(0, MAX_SEQUENCE_NUMBER)]
self.nakSent = False
self.ackSent = False
self.recentACK = Frame(self.senderAddress, self.receiverAddress, 1, 0,
"Acknowledgement Frame")
self.eot = False
self.lastACKsent = None
def validSEQ(self, seq_no: int):
"""Function to check if the sequence number of incoming frame lies within window"""
if ((self.front <= seq_no and seq_no < self.end)
or (self.end < self.front and self.front <= seq_no)
or (seq_no < self.end and self.end < self.front)):
return True
else:
return False
def sendAck(self):
"""Function for building and sending ACK frame"""
frame = Frame(self.senderAddress, self.receiverAddress,
self.frameType['ack'], self.front,
'acknowledgement frame')
self.recentACK = frame
print("Sent ACK", self.front)
self.connection.send(str.encode(frame.toBinaryString(22)))
self.lastACKsent = time.time()
def sendNak(self):
"""Function for building and sending NAK frame"""
frame = Frame(self.senderAddress, self.receiverAddress,
self.frameType['nak'], self.front, 'not acknowledgement')
self.connection.send(str.encode(frame.toBinaryString(22)))
print("Sent NAK", self.front)
def resendPreviousACK(self):
"""Function for resending last ACK on timeout"""
while (not self.eot):
if (self.lastACKsent == None):
continue
elapsedTime = time.time() - self.lastACKsent
if (elapsedTime > 1):
self.connection.send(
str.encode(self.recentACK.toBinaryString(22)))
self.lastACKsent = time.time()
def startReceiving(self):
"""Function for receiving frames"""
time.sleep(0.4)
ACKresendingThread = threading.Thread(target=self.resendPreviousACK)
ACKresendingThread.start()
# wait for data and receive
data = self.connection.recv(576).decode()
total_data = ""
while data != "end":
# build frame from binary data string
frame = Frame.build(data)
print("\nSTATUS: FRAME RECEIVED")
if not frame.hasError():
print("STATUS: NO ERROR FOUND")
seqNo = frame.getSeqNo()
# if frame other than first one got, send NAK
if (seqNo != self.front and self.nakSent == False):
self.sendNak()
self.nakSent = True
# if seq no within the window accept it
if (self.validSEQ(seqNo) and self.filled_up[seqNo] == False):
self.filled_up[seqNo] = True
self.window[seqNo] = frame.getData()
print(frame.getData())
# take the received data sequentially into the final data string
# update the front, end of the window accordingly (also update flags)
while (self.filled_up[self.front] == True):
total_data += self.window[self.front]
self.filled_up[self.front] = False
self.front = (self.front + 1) % MAX_SEQUENCE_NUMBER
self.end = (self.end + 1) % MAX_SEQUENCE_NUMBER
self.ackSent = True
print("STATUS: FRAME RECEIVED SUCCESSFULLY")
# if sequential frame received, send acknowledgement
if (self.ackSent):
self.sendAck()
self.ackSent = False
self.nakSent = False
# discard erroneous frame
else:
print("STATUS: ERRONEOUS FRAME")
# wait and receive next frame
data = self.connection.recv(576).decode()
# stop the resending-acknowledgement thread
self.eot = True
ACKresendingThread.join()
# write the whole data into file
file = open(self.filename, 'w')
file.write(total_data)
file.close()
