TFTP_client python实现（个人备忘）

#coding=utf-8
from socket import *
import time,struct

class TFTPClient():
    # 操作码
    DOWNLOAD    = 1
    UPLOAD      = 2
    DATA        = 3
    ACK         = 4
    ERROR       = 5

    def __init__(self, ip = "192.168.38.1", port = 69):
        self.udpSocket = socket(AF_INET, SOCK_DGRAM)
        # 服务器信息
        self.serverAddr = (ip, port)

    def download(self, fileName):
        self.udpSocket = socket(AF_INET, SOCK_DGRAM)
        # fileName must be bytes
        fileName = fileName.encode()
        # 发送下载请求
        req = struct.pack(str("!H%dsb5sb" % len(fileName)), 1, fileName, 0, b"octet", 0)
        self.udpSocket.sendto(req, self.serverAddr)
        print("客户端启动！请求下载文件：%s" % fileName)

        #帧计数，用于数据校验
        recvFrameNum = 1
        try :
            #等待服务器发送数据
            while True:
                #接收数据
                recvData, recvAddr = self.udpSocket.recvfrom(1024)
                #数据帧： 操作码2 快编号2 数据n
                cmdType, frameNum = struct.unpack("!HH", recvData[:4])
                # 判断接收的是否是“数据”
                if cmdType == self.DATA and frameNum == recvFrameNum:
                    print("接收到第%d帧数据！"%frameNum) #for test
                    # 打开文件
                    if frameNum == 1:
                        fileRecv = open("download.txt", "ab")
                        fileRecv.write(b"#"*30+time.strftime("%Y-%m-%d %H:%M:%S").encode()+b"#"*30+b"\n")

                    fileRecv.write(recvData[4:])

                    # 响应 : 操作码2 快编号2
                    ack = struct.pack("!HH", self.ACK, frameNum)
                    self.udpSocket.sendto(ack, recvAddr)

                    #判断是否发送完
                    if len(recvData) < 516 :
                        fileRecv.close()
                        fileRecv = None
                        print("接收完毕， 关闭文件。")
                        break

                    #计数+1
                    recvFrameNum += 1

                elif cmdType == self.ERROR:
                    print("服务器返回异常，退出！")
                    break
        finally:
            if fileRecv != None:
                fileRecv.close()

    def upload(self, fileName):
        # 若此处不新建套接字，当重复使用时会出现异常
        self.udpSocket = socket(AF_INET, SOCK_DGRAM)
        # fileReq = None
        # fileName must be bytes
        fileName = fileName.encode()
        # 发送上传请求
        req = struct.pack(str("!H%dsb5sb" % len(fileName)), self.UPLOAD, fileName, 0, b"octet", 0)
        self.udpSocket.sendto(req, self.serverAddr)
        print("客户端启动！请求上传！")

        # 等待服务器就绪
        recvData, recvAddr = self.udpSocket.recvfrom(1024)
        cmdType, frameNum = struct.unpack("!HH", recvData[:4])
        if cmdType != self.ACK or frameNum != 0:
            print("服务器相应失败！")
            return False

        try:
            # fileReqName = self.recvData[2:-7].decode()
            print("客户端请求上传文件：%s" % fileName)
            # 打开文件
            try:
                fileUpload = open(fileName, "rb")
            except:
                print("文件 《%s》 不存在" % fileName)
                # 向 client 发送异常信息
                errInfo = struct.pack("!HHHb", 5, 5, 5, 0)
                self.udpSocket.sendto(errInfo, recvAddr)
                return False

            # 初始化块编号
            frameNum = 1

            while True:
                fileData = fileUpload.read(512)
                # 打包
                # frameData = struct.pack(str("!HH%ds" % len(fileData)), 3, frameNum, fileData)
                frameData = struct.pack(str("!HH"), 3, frameNum) + fileData
                # 发送
                for i in range(0, 3):
                    self.udpSocket.sendto(frameData, recvAddr)

                    # 若文件已发送完成
                    if len(fileData) < 512:
                        print("文件发送完成！")
                        fileUpload.close()
                        fileUpload = None
                        return True

                    # 等待 server 响应
                    # 接收数据
                    recvData, recvAddr = self.udpSocket.recvfrom(1024)
                    cmdType, recvFrameNum = struct.unpack("!HH", recvData[:4])
                    if cmdType == self.ACK and recvFrameNum == frameNum:
                        break
                    elif i == 3:
                        print("链接异常，取消发送")
                        # 向 client 发送异常信息
                        errInfo = struct.pack("!HHHb", 5, 5, 5, 0)
                        self.udpSocket.sendto(errInfo, recvAddr)
                        exit()

                # 编号+1
                frameNum += 1
        finally:
            if fileUpload != None:
                fileUpload.close()

#文件名
# fileName = b"text.txt"
client = TFTPClient()
client.download("text.txt")
client.upload("text.txt")