70 lines
2.2 KiB
Python
Executable File
70 lines
2.2 KiB
Python
Executable File
import socket
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import random
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class NetworkLayer:
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def __init__(self, host:str, port:int) -> None:
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self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
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self.socket.connect((host, port))
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print("下层的不可靠传输连接成功，等待发送方传输。")
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def udt_send(self, data:str):
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self.socket.send(data.encode())
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def udt_rcv(self) -> str:
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message = self.socket.recv(12).decode("utf-8")
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return message
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def close(self):
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self.socket.close()
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class ApplicationLayer:
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def __init__(self) -> None:
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self.data = list()
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class Receiver:
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def __init__(self, networkLayer:NetworkLayer, applicationLayer:ApplicationLayer):
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self.expected_seq_num = 1
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self.networkLayer = networkLayer
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self.applicationLayer = applicationLayer
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def deliver_data(self, data, seq_num):
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if seq_num == self.expected_seq_num:
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print(f'成功收到seq_num={seq_num}, data=\"{data}\"的包。')
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self.applicationLayer.data.append(data)
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self.udt_send(seq_num)
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self.expected_seq_num += 1
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else:
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print(f'收到seq_num={seq_num}, 与预期seq_num={self.expected_seq_num}不符。')
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self.udt_send(self.expected_seq_num - 1)
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def udt_send(self, ack_num):
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print(f"发送ACK={ack_num}", end="")
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if random.random() > 0.25:
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self.networkLayer.socket.send("{:0>4d}".format(ack_num).encode())
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else:
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print("，此包丢失。", end="")
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print()
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def extract(self, message:str):
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seq_num = int(message[:3])
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data = message[4:]
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return seq_num, data
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if __name__ == "__main__":
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max_seq_num = 20
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networkLayer = NetworkLayer(host="192.168.31.197", port=23666)
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applicationLayer = ApplicationLayer()
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receiver = Receiver(networkLayer, applicationLayer)
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while True:
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message = networkLayer.udt_rcv()
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if message:
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seq_num, data = receiver.extract(message)
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receiver.deliver_data(data, seq_num)
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if receiver.expected_seq_num > max_seq_num:
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break
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print("序列传输完成。")
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networkLayer.close()
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