TFTP下载
TFTP下载器流程图.png
#构造下载请求数据
cmd_buf = struct.pack("!H8sb5sb",1,"test.jpg",0,"octet",0)
#解析返回数据格式
cmdTuple = struct.unpack("!HH", recvData[:4])
#构造ACK(应答包)
ackBuf = struct.pack("!HH",4,p_num)
TFTP数据包格式.png
from socket import *
import struct
import sys
if len(sys.argv) != 2:
print('-'*30)
print("tips:")
print("python xxxx.py 192.168.1.1")
print('-'*30)
exit()
else:
ip = sys.argv[1]
# 创建udp套接字
udpSocket = socket(AF_INET, SOCK_DGRAM)
#构造下载请求数据
cmd_buf = struct.pack("!H8sb5sb",1,"test.jpg",0,"octet",0)
#发送下载文件请求数据到指定服务器
sendAddr = (ip, 69)
udpSocket.sendto(cmd_buf, sendAddr)
p_num = 0
recvFile = ''
while True:
recvData,recvAddr = udpSocket.recvfrom(1024)
recvDataLen = len(recvData)
# print recvAddr # for test
# print len(recvData) # for test
cmdTuple = struct.unpack("!HH", recvData[:4])
# print cmdTuple # for test
cmd = cmdTuple[0]
currentPackNum = cmdTuple[1]
if cmd == 3: #是否为数据包
# 如果是第一次接收到数据，那么就创建文件
if currentPackNum == 1:
recvFile = open("test.jpg", "a")
# 包编号是否和上次相等
if p_num+1 == currentPackNum:
recvFile.write(recvData[4:]);
p_num +=1
print '(%d)次接收到的数据'%(p_num)
ackBuf = struct.pack("!HH",4,p_num)
udpSocket.sendto(ackBuf, recvAddr)
# 如果收到的数据小于516则认为出错
if recvDataLen<516:
recvFile.close()
print '已经成功下载！！！'
break
elif cmd == 5: #是否为错误应答
print "error num:%d"%currentPackNum
break
udpSocket.close()
