GBN_Server.py

import select
import socket
import sys
from random import random

from GBN.Data import Data

class GBNServer:
    def __init__(self):
        self.nextseqnum = 1
        self.addr = ('127.0.0.1', 31500)
        self.client_addr = ('127.0.0.1', 12345)
        self.socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
        self.socket.bind(self.addr)
        self.max_time = 5 # 超时时间
        self.wait_time = 15 # 等待看是否还有数据发来的时间
        self.pkg_num = 0
        self.N = 3 # 窗口大小
        self.buff_size = 1024
        self.send_windows = []

    def send(self, buffer):
        # 计时和包序号初始化
        pkg_timer = 0
        self.pkg_num = len(buffer)
        # 记录上一个回执的ack的值
        last_ack = 0
        msg_timer = 0

        while True:
            # 当超时后，将窗口内的数据更改为未发送状态
            if pkg_timer > self.max_time:
                resend = []
                for data in self.send_windows:
                    data.state = 0
                    resend.append(data.seq)
                if len(resend) > 0:
                    print('Client: 发生超时，重传', resend)

            # 窗口中数据少于最大容量时，尝试添加新数据
            while len(self.send_windows) < self.N:
                if(self.nextseqnum > self.pkg_num):
                    break
                # 将第nextseqnum-1个包加入窗口内，并封装成数据,type为0
                data = Data(buffer[self.nextseqnum-1], 0, seq=self.nextseqnum)
                self.send_windows.append(data)
                self.nextseqnum += 1

            # 窗口内无数据则退出总循环
            if not self.send_windows:
                if pkg_timer > self.max_time and msg_timer > self.wait_time:
                    print('Server: 发送/接收完毕, 退出')
                    break

            # 遍历窗口内数据，如果存在未成功发送的则发送
            for data in self.send_windows:
                if not data.state:
                    print('Server: 发送数据 ', data.seq)
                    self.socket.sendto(str(data).encode(), self.client_addr)
                    data.state = 1

            # 无阻塞socket连接监控
            readable, writeable, errors = select.select([self.socket, ], [], [], 1)

            if len(readable) > 0:
                message, address = self.socket.recvfrom(self.buff_size)
                msg = message.decode()
                if msg[1] == '1':
                    # 收到ACK， 重新计时
                    pkg_timer = 0
                    print('Server: 收到ACK ', msg[0])
                    ack_num = msg[0]
                    for i in range(len(self.send_windows)):
                        if ack_num == self.send_windows[i].seq:
                            self.send_windows = self.send_windows[i + 1:]
                            break
                else:
                    pkg_timer += 1
                    # 非ACK，说明是收到的数据
                    print('Server: 收到MSG = ', msg[0])
                    ackNum = int(msg[0])
                    msg_timer = 0
                    # 连续接收数据则反馈当前ack
                    if last_ack == ackNum - 1:
                        # 丢包率为0.2
                        if random() < 0.1:
                            print('Server: 模拟发生丢包, 丢失的包的seq为', str(ackNum))
                            continue
                        if random() < 0.1:
                            print('Server: 模拟ACK丢失, 丢失ACK为 ', str(ackNum))
                            last_ack = ackNum
                            continue
                        self.socket.sendto(str(Data(''.encode(), 1, ackNum)).encode(), address)
                        print('Server: 发送ACK ', str(ackNum))
                        last_ack = ackNum
                    else:
                        print('Server: 收到的MSG不是需要的，发送当前收到的最大的ACK ', last_ack)
                        self.socket.sendto(str(Data(''.encode(), 1, last_ack)).encode(), address)
            else:
                # 未收到数据则计时器加一
                pkg_timer += 1
                msg_timer += 1

    def start(self):
        # 读取文件
        buffer = []
        with open('server_send.txt', 'rb') as f:
            while True:
                seq = f.read(500)
                if len(seq) > 0:
                    buffer.append(seq)
                else:
                    break
        while True:
            # 无阻塞socket连接监控
            readable, writeable, errors = select.select([self.socket, ], [], [], 1)
            if (len(readable) > 0):
                message, address = self.socket.recvfrom(self.buff_size)
                if message.decode() == '-testgbn':
                    self.send(buffer)

s = GBNServer()
s.start()