python实现文件下载

# -*- coding:utf-8 -*-

import struct
from socket import *
import time
import os

def main():


	#0. 获取要下载的文件名字:
	downloadFileName = input("请输入要下载的文件名:")

	#1.创建socket
	udpSocket = socket(AF_INET, SOCK_DGRAM)

	requestFileData = struct.pack("!H%dsb5sb"%len(downloadFileName), 1, downloadFileName, 0, "octet", 0)

	#2. 发送下载文件的请求
	udpSocket.sendto(requestFileData, ("192.168.0.107", 69))

	flag = True #表示能够下载数据，即不擅长，如果是false那么就删除
	num = 0
	f = open(downloadFileName, "w")

	while True:
		#3. 接收服务发送回来的应答数据
		responseData = udpSocket.recvfrom(1024)

		# print(responseData)
		recvData, serverInfo = responseData

		opNum = struct.unpack("!H", recvData[:2])

		packetNum = struct.unpack("!H", recvData[2:4])

		print(packetNum[0])

		# print("opNum=%d"%opNum)
		# print(opNum)

		# if 如果服务器发送过来的是文件的内容的话:
		if opNum[0] == 3: #因为opNum此时是一个元组(