python3 socket 实现TFTP 文件下载

本代码运行环境：python3 + Ubuntu16
1：运行代码前需要运行tftp服务器端，把要上传的文件放在和执行文件同一个文件夹里
2：tftp服务器端ip要和ubuntu ip在同一网段

相关知识可以参考上一篇文章

粗糙的实现代码如下

# coding=utf-8
from socket import *
import struct
import sys


# 接收命令传进来的参数
if len(sys.argv) != 2:
    print('-'*30)
    print('run tips:')
    print('python3 filename destination_ip')
    print('-'*30)
    exit()
else:
    ip = sys.argv[1]


tftp_udp = socket(AF_INET, SOCK_DGRAM)
tftp_data = struct.pack("!H8sb5sb", 1, b"test.jpg", 0, b"octet", 0)  # python3
# tftp_data = struct.pack("!H8sb5sb", 1, "test.jpg", 0, "octet", 0)  # python
# 发送下载请求

bind_address = (ip, 69)
tftp_udp.sendto(tftp_data, bind_address)

receive_file = ''
num = 1

# 接收数据
while True:
    receive_data, receive_address = tftp_udp.recvfrom(1024)
    data_len = len(receive_data)
    data_unpack = struct.unpack('!HH', (receive_data[:4]))
    
    # 数据包拆分
    pack_num = data_unpack[0]  # 操作码
    return_num = data_unpack[1]  # 块编号

# 判断数据操作码，进行操作
    # 操作码3，下载数据
    if pack_num == 3:
        if return_num == 1:
            receive_file = open('test.jpg', 'ba')
        if num == return_num:
            receive_file.write(receive_data[4:])
            print('\r(%d)receive file' % num, end='')
            # 构建ack确认接收成功
            return_ack = struct.pack("!HH", 4, num)
            tftp_udp.sendto(return_ack, receive_address) # 发送确认
            num += 1
        if data_len < 516:
            receive_file.close()
            print('Download successful !')
            break
    # 操作码5,错误
    if pack_num == 5:
        print('error num: %d' % return_num)

tftp_udp.close()