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client.py
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client.py
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"""
The module for the client class of the file transfer application using UDP
"""
import sys
import time
from typing import Tuple
from socket import timeout
from lib.parser import parse_args
from lib.connection import Connection
from lib.segment import Segment
from lib.constants import ACK_FLAG, SYN_ACK_FLAG, SYN_FLAG, DEFAULT_IP, FIN_FLAG, TIMEOUT_LISTEN, FIN_ACK_FLAG
class Client:
"""
The client class of the file transfer application using UDP
The client should be able to:
1. Establishes a three-way handshake connection with the server
2. Receives the file from the server
3. Sends the acknowledgement to the server
"""
def __init__(self):
client_port, broadcast_port, output_file, server_ip, client_ip = parse_args(
False)
if server_ip is None:
server_ip = DEFAULT_IP
if client_ip is None:
client_ip = DEFAULT_IP
self.server_ip = server_ip
self.client_port = client_port
self.broadcast_port = broadcast_port
self.output_file = output_file.split("/")[-1]
self.file = self.create_file()
self.conn = Connection(
ip=client_ip,
port=self.client_port,
broadcast=self.broadcast_port,
as_server=False
)
self.segment = Segment()
def create_file(self):
"""Create the output file"""
try:
file = open(f"received_file/{self.output_file}", "wb")
return file
except FileNotFoundError:
print(f"[!] {self.output_file} doesn't exists. Client exiting...")
sys.exit(1)
def close_file(self):
"""Close the output file"""
self.file.close()
def connect(self):
"""Connect"""
self.conn.send(
self.segment.to_bytes(), self.server_ip, self.conn.broadcast_port
)
def acknowledge(self, seq_number: int, server_address: Tuple[str, str]):
"""Send acknowledge to the server"""
response = Segment()
response.set_flag(["ACK"])
response_header = response.get_header()
response_header["seq"] = seq_number
response_header["ack"] = seq_number + 1
response.set_header(response_header)
self.conn.send(response.to_bytes(),
server_address[0], server_address[1])
def three_way_handshake(self):
"""
Establishes a three-way handshake connection with the server
1. Send SYN to server
2. Receive SYN-ACK from server
3. Send ACK to server
"""
while True:
server_addr = (self.server_ip, self.broadcast_port)
try:
data, server_addr = self.conn.listen_segment()
self.segment = Segment.from_bytes(data)
if self.segment.get_flag() == SYN_FLAG:
self.segment.set_flag(["SYN", "ACK"])
header = self.segment.get_header()
header["ack"] = header["seq"] + 1
header["seq"] = 0
self.segment.set_header(header)
print(
f"[ INFO ] [Server {server_addr[0]}:{server_addr[1]}] received SYN from client"
)
self.conn.send(self.segment.to_bytes(), *server_addr)
elif self.segment.get_flag() == SYN_ACK_FLAG:
print(
f"[ INFO ] [Server {server_addr[0]}:{server_addr[1]}] sent SYN-ACK to client"
)
self.conn.send(self.segment.to_bytes(), *server_addr)
elif self.segment.get_flag() == ACK_FLAG:
print(
f"[ INFO ] [Server {server_addr[0]}:{server_addr[1]}] received ACK from client"
)
print(
f"[ INFO ] [Server {server_addr[0]}:{server_addr[1]}] Three-way handshake established"
)
break
else:
print(
f"[ INFO ] [Server {server_addr[0]}:{server_addr[1]}] already received segment file, resetting connection"
)
self.segment.set_flag(["SYN", "ACK"])
header = self.segment.get_header()
header["ack"] = header["seq"] + 1
header["seq"] = 0
self.segment.set_header(header)
print(
f"[ INFO ] [Server {server_addr[0]}:{server_addr[1]}] sent SYN-ACK to client"
)
self.conn.send(self.segment.to_bytes(), *server_addr)
except timeout:
if self.segment.get_flag() == SYN_FLAG:
print(
f"[ TIMEOUT ] [Server {server_addr[0]}:{server_addr[1]}] ACK response timeout, resending SYN"
)
self.conn.send(self.segment.to_bytes(), *server_addr)
else:
print(
f"[ TIMEOUT ] [Server {server_addr[0]}:{server_addr[1]}] SYN response timeout"
)
def shutdown(self):
"""Shutdown the client"""
self.close_file()
self.conn.close()
def listen_file_transfer(self):
"""Listen for file transfer attempt from server"""
# File transfer, client-side, receive file from a server
# SYN : 0
# ACK : 1
# Metadata : 2
metadata_seq_number = 2
is_metadata_received = False
seq_number = 3
while True:
try:
data, server_address = self.conn.listen_segment()
if server_address[1] != self.broadcast_port:
print(
f"[ WARNING ] [Server {server_address[0]}:{server_address[1]}] Received Segment {self.segment.get_header()['seq']} [Wrong port]"
)
else:
self.segment = Segment.from_bytes(data)
# Received data fails checksum
if not self.segment.is_valid():
print(
f"[ WARNING ] [Server {server_address[0]}:{server_address[1]}] Received Segment {self.segment.get_header()['seq']} [Segment Corrupted]"
)
# Received valid metadata when metadata haven't been received
elif (self.segment.get_header()["seq"] == metadata_seq_number
and not is_metadata_received
):
payload = self.segment.get_payload()
metadata = payload.decode().split(",")
print(
f"[ INFO ] [Server {server_address[0]}:{server_address[1]}] Received Filename: {metadata[0]}, File Extension: {metadata[1]}, File Size: {metadata[2]}"
)
print(
f"[ INFO ] [Server {server_address[0]}:{server_address[1]}] Sending ACK {metadata_seq_number + 1}"
)
self.acknowledge(self.segment.get_header()[
"seq"], server_address)
# Prevent the loop from continuing, which would cause ACK to be sent twice
continue
# Received valid data that is next in line to be received
elif (self.segment.get_header()["seq"] == seq_number
):
print(
f"[ INFO ] [Server {server_address[0]}:{server_address[1]}] Received Segment {seq_number}"
)
payload = self.segment.get_payload()
self.file.write(payload)
print(
f"[ INFO ] [Server {server_address[0]}:{server_address[1]}] Sending ACK {seq_number + 1}"
)
self.acknowledge(seq_number, server_address)
seq_number += 1
# Prevent the loop from continuing, which would cause ACK to be sent twice
continue
# End of File
elif self.segment.get_flag() == FIN_ACK_FLAG:
print(
f"[ INFO ] [Server {server_address[0]}:{server_address[1]}] Received FIN-ACK"
)
break
# Received previously received data
elif self.segment.get_header()["seq"] < seq_number:
print(
f"[ WARNING ] [Server {server_address[0]}:{server_address[1]}] Received Segment {self.segment.get_header()['seq']} [Duplicate]"
)
elif self.segment.get_header()["seq"] > seq_number:
print(
f"[ WARNING ] [Server {server_address[0]}:{server_address[1]}] Received Segment {self.segment.get_header()['seq']} [Out-Of-Order]"
)
self.acknowledge(seq_number, server_address)
except timeout:
print(
f"[ WARNING ] [Server {server_address[0]}:{server_address[1]}] Received Segment {self.segment.get_header()['seq']} [Timeout]"
)
self.acknowledge(seq_number, server_address)
self.closing_connection(seq_number, server_address)
def closing_connection(self, seq_number, server_address):
"""Received FIN-ACK, starting the protocol to close connection"""
# Send ACK
print(
f"[ INFO ] [Server {server_address[0]}:{server_address[1]}] Sending ACK")
self.acknowledge(seq_number, server_address)
# Send FIN-ACK
print(
f"[ INFO ] [Server {server_address[0]}:{server_address[1]}] Sending FIN-ACK")
fin_ack_segment = Segment()
fin_ack_segment.set_header({
"ack": seq_number,
"seq": seq_number
})
fin_ack_segment.set_flag(["FIN", "ACK"])
self.conn.send(fin_ack_segment.to_bytes(),
server_address[0], server_address[1])
is_ack_received = False
time_limit = time.time() + TIMEOUT_LISTEN
while not is_ack_received:
try:
data, _ = self.conn.listen_segment()
ack_segment = Segment.from_bytes(data)
if ack_segment.get_flag() == ACK_FLAG:
print(
f"[ SUCCESS ] [Server {server_address[0]}:{server_address[1]}] ACK received, closing down connection."
)
is_ack_received = True
except timeout:
if time.time() > time_limit:
print(
f"[ WARNING ] [Server {server_address[0]}:{server_address[1]}] [Timeout] Client waited too long, connection closed."
)
break
print(
f"[ WARNING ] [Server {server_address[0]}:{server_address[1]}] [Timeout] Resending FIN ACK."
)
self.conn.send(fin_ack_segment.to_bytes(),
server_address[0], server_address[1])
# ACK received from server
print(
f"[ SUCCESS ] [Server {server_address[0]}:{server_address[1]}] Data received successfuly"
)
print(
f"[ INFO ] [Server {server_address[0]}:{server_address[1]}] File written to received_file/{self.output_file}"
)
if __name__ == "__main__":
CLIENT = Client()
CLIENT.connect()
CLIENT.three_way_handshake()
CLIENT.listen_file_transfer()
CLIENT.shutdown()