首先,TFTP协议遵循以下格式:

tftp协议

我们只需要根据这些协议, 来决定我们每次请求数据是什么

构造请求数据时的注意点:(struct的格式)
例如

fileName = "123456.jpg"
dlreq = struct.pack("!H10sb5sb", 1, fileName.encode("utf-8"), 0, b"octet", 0)

注意: "!H10sb5sb"中, H标示两个字节, s表示一个字节, b标示1个字节. 具体含义如下图:

fmt的格式

• 注1.q和Q只在机器支持64位操作时有意思

• 注2.每个格式前可以有一个数字，表示个数

• 注3.s格式表示一定长度的字符串，4s表示长度为4的字符串，但是p表示的是pascal字符串

• 注4.P用来转换一个指针，其长度和机器字长相关

• 注5.最后一个可以用来表示指针类型的，占4个字节

符号fmt

然后上代码:

from socket import *
import struct
import sys
from threading import Thread

g_ip = ""
g_port = 0



def downLoad():

    g_socket = socket(AF_INET, SOCK_DGRAM)
    g_socket.bind(("", 9090))
    fileName = input("请输入要下载的文件名: ")
    fileNameLen = len(fileName)
    # 下载请求格式控制字符串
    dlreqStr = "!H" + str(fileNameLen) + "sb5sb"
    # 构造下载请求数据
    dlreq = struct.pack(dlreqStr, 1, fileName.encode("utf-8"), 0, b"octet", 0)

    sendAdd = (g_ip, g_port)
    g_socket.sendto(dlreq, sendAdd)

    p_Num = 0
    recvfile = ""

    while True:
        recvData, recvAddr = g_socket.recvfrom(1024)
        recvdataLen = len(recvData)
        cmd_tuple = struct.unpack("!HH", recvData[:4])
        cmd = cmd_tuple[0]
        currentPackNum = cmd_tuple[1]
        if cmd == 3:
            if currentPackNum == 1:
                recvfile = open(fileName, "wb")

            if p_Num + 1 == currentPackNum:
                recvfile.write(recvData[4:])
                p_Num += 1
                print("第 %d 次接收到数据"%p_Num)

                ackBuf = struct.pack("!HH", 4, p_Num)
                g_socket.sendto(ackBuf, recvAddr)

            if recvdataLen < 516:
                recvfile.close()
                print("已经下载成功!")
                break

        elif cmd == 5:
            print("错误!! 错误块: %d"%currentPackNum)
            break

    recvfile.close()
    g_socket.close()



def upLoad():
    upSocket = socket(AF_INET, SOCK_DGRAM)
    num = 0
    
    fileName = input("输入要上传的文件:")
    sendAdd = (g_ip, g_port)

    fileNameLen = len(fileName)
    # 上传请求格式控制字符串
    ulreqStr = "!H" + str(fileNameLen) + "sb5sb"
    # 构造下载请求数据
    ulreq = struct.pack(ulreqStr, 2, fileName.encode("utf-8"), 0, b"octet", 0)

    upSocket.sendto(ulreq, sendAdd)

    recvData1 = upSocket.recvfrom(1024)
    rand_port = recvData1[1][1]
    ack_num = struct.unpack("!H",recvData1[0][2:4])
    sendAdd = (g_ip, rand_port)

    try:
        fileRead = open(fileName, 'rb')
    except:
        errorData = struct.pack("!HHHb", 5, 5, 5, num)
        upSocket.sendto(errorData, sendAdd)
        exit() # 退出线程

    while True:
        readData = fileRead.read(512)
        sendData = struct.pack("!HH", 3, num) + readData
        upSocket.sendto(sendData, sendAdd)

        if len(sendData) < 516:
            print("传输成功!!")
            break

        recv_ack = upSocket.recvfrom(1024)[0]
        recv_cmd, ack_num = struct.unpack("!HH", recv_ack)

        print("接收到了 %d", ack_num)

        num +=1

        if int(recv_cmd) != 4 or int(ack_num != num - 1):
            break
    upSocket.close()
    fileRead.close()





def main():

    global g_ip
    global g_port


    g_ip = input("请输入ip地址: ")
    g_port = int(input("请输入端口号: "))

    t1 = Thread(target = upLoad)

    t1.start()
    t1.join()
    
if __name__ == "__main__":
    main()