Python的网络编程[2] -> TFTP 协议[1] -> TFTP 的 Python 实现

TFTP实现 / TFTP Implement

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目录

1. TFTP 的服务器建立过程
2. TFTP 的客户端建立过程

1 TFTP 的服务器建立过程

服务器建立步骤主要有:

（1）      设定服务器IP和端口号(常用69)，建立socket并bind地址;

（2）      设定服务器工作目录;

（3）      建立主循环进行监听，根据收到的信息选择读/写模式;

（4）      （建立新的线程及socket）执行上传下载操作;

（5）      下载操作: block number设置为1—打开需要下载的文件—进入循环—读取512byte数据—发送读取的数据—等待ACK报文（超时重发）—确认opcode—确认数据长度是否结束（结束则进行结束处理，并关闭文件）11—block number +1;

（6）      上传操作: block number 设置为0—发送ACK报文—block number +1—打开新的文件存储上传数据—进入循环—等待接收DATA报文—确认opcode—写入数据—发送ACK报文—确认数据长度是否结束（结束则进行结束处理，并关闭文件）—block number +1。

Note: 关于THTP_Helper 的 TFTP 的加解码过程请参考 TFTP 加解码部分

 import importlib
 from TFTP_Helper import *
 import socket
 from threading import Thread

 class TFTPServer():
     def __init__(self):
         ip = '127.0.0.1'
         port = 69
         address = (ip, port)
         self.home_path = 'TFTPServerFile'
         self.server = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
         self.server.bind(address)

     def readRequest(self, file_name, addr):
         print('<<< RRQ', '\n=== Read request, starting file %s downing to client' % file_name, end='')
         sock_down = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
         block_num = 1
         try:
             f = open(self.home_path + '\\' + file_name, 'rb')
         except:
             # file no found, exit thread
             print('=== File %s no found' % file_name)
             exit()
         while True:
             down_data = f.read(512)     # data is byte format
             sock_down.sendto(TFTPData.encode(block_num, down_data), addr)
             print('>>> DATA', block_num)
             ack_msg, ack_addr = sock_down.recvfrom(1024)
             print('<<< ACK ', block_num)
             opcode, ack_block_num = TFTPAck.decode(ack_msg)
             assert opcode == 4 and ack_block_num == block_num, 'Invalid ack message.'
             if len(down_data) < 512:
                 block_num = 1
                 print('=== Transmission of %s completed' % file_name)
                 f.close()
                 exit()
             block_num += 1
         print('=== Close file')
         f.close()

     def writeRequest(self, file_name, addr):
         print('<<< WRQ', '\n=== Write request, starting file %s uploading to server' % file_name)
         sock_upload = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
         block_num = 0
         sock_upload.sendto(TFTPAck.encode(block_num), addr)
         print('>>> ACK')
         try:
             f = open('TFTPServerFIle\\Copy-'+file_name, 'wb')
         except:
             print('=== File "%s" no found' % file_name)
             exit()
         block_num += 1
         while True:
             recv_data, addr = sock_upload.recvfrom(1024)
             opcode, block_num_recv, data = TFTPData.decode(recv_data)
             print('<<< DATA')
             if opcode != 3 or block_num != block_num_recv:
                 print('=== Error Opcode or Block Number')
                 # TODO: add error msg send and handle here
                 exit()
             f.write(data)
             sock_upload.sendto(TFTPAck.encode(block_num), addr)
             print('>>> ACK')
             if len(data) < 512:
                 # TODO: add transmission completed handle here
                 block_num = 1
                 print('=== File "%s" transmission completed' % file_name)
                 f.close()
                 exit()
             block_num += 1

     def server_run(self):
         while True:
             print('=== Waiting client')
             msg, addr = self.server.recvfrom(1024)
             print('<<< Receive a connection from client %s, msg is %s' % (addr, msg))
             opcode, file_name = TFTPReadWriteRequest.decode(msg)
             cmdSelect = {1: Thread(target=self.readRequest, args=(file_name, addr)),
                          2: Thread(target=self.writeRequest, args=(file_name, addr))}
             try:
                 cmdSelect[opcode].start()
             except:
                 print('<<< Receive error opcode%s' % opcode)
                 raise ErrorOpcode

 server = TFTPServer()
 server.server_run()

2 TFTP 的客户端建立过程

客户端建立步骤主要有:

（1）      获取服务器ip和端口;

（2）      下载操作: 建立下载socket—发送RRQ下载请求—设置block number为1—新建文件存储下载数据—进入循环—等待接收DATA报文—确认opcode—写入数据—发送ACK报文—确认数据长度是否结束（结束则进行结束处理，并关闭文件）—block number +1;

（3）      上传操作: 建立上传socket—发送WRQ上传请求—等待ACK报文—设置block number为0—确认opcode—打开需要上传的文件—进入循环—读取数据—发送DATA报文—接收ACK报文—确认opcode—确认数据长度是否结束（结束则进行结束处理，并关闭文件）—block number +1;

 from TFTP_Helper import *
 import socket

 class TFTPClient():
     def __init__(self):
         server_ip = '127.0.0.1'
         port = 69
         self.address = (server_ip, port)

     def readRequest(self, file_name):
         sock_down = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
         send_data = TFTPReadWriteRequest.encode('r', file_name)
         sock_down.sendto(send_data, self.address)
         block_num = 1
         try:
             f = open('TFTPClientFIle\copy-'+file_name, 'wb')
         except:
             print('--- File "%s" no found' % file_name)
             exit()
         while True:
             recv_data, recv_addr = sock_down.recvfrom(1024)
             print('<<< DATA', block_num)
             opcode, block_num_recv, data = TFTPData.decode(recv_data)
             if opcode != 3 or block_num != block_num_recv:
                 print('--- Opcode or Block Number Error')
                 # TODO: add error msg send and handle here
                 break
             f.write(data)
             sock_down.sendto(TFTPAck.encode(block_num), recv_addr)
             print('>>> ACK ', block_num)
             if len(data) < 512:
                 # TODO: add transmission completed handle here
                 block_num = 1
                 print('--- File "%s" transmission completed' % file_name)
                 f.close()
                 break
             block_num += 1

     def writeRequest(self, file_name):
         sock_upload = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
         send_data = TFTPReadWriteRequest.encode('w', file_name)
         sock_upload.sendto(send_data, self.address)
         print('>>> WRQ')
         recv_data, addr = sock_upload.recvfrom(1024)
         print('<<< ACK')
         opcode, ack_block = TFTPAck.decode(recv_data)
         block_num = 0
         if opcode != 4 or ack_block != block_num:
             print('--- Error Opcode or Block Number')
             # TODO: add error msg send and handle here
             exit()
         try:
             f = open('TFTPClientFIle\\'+file_name, 'rb')
         except:
             print('--- File "%s" no found' % file_name)
             exit()
         block_num += 1
         while True:
             upload_data = f.read(512)
             sock_upload.sendto(TFTPData.encode(block_num, upload_data), addr)
             print('>>> DATA')
             ack_msg, addr = sock_upload.recvfrom(1024)
             print('<<< ACK')
             opcode, ack_block_num = TFTPAck.decode(ack_msg)
             assert opcode == 4 and ack_block_num == block_num, 'Invalid ack message.'
             if len(upload_data) < 512:
                 # TODO: add transmission completed handle here
                 block_num = 1
                 print('--- File "%s" transmission completed' % file_name)
                 f.close()
                 break
             block_num += 1

 tftp = TFTPClient()
 for file in ['downFile.py', 'downFile.docx', 'downFile.txt', 'downFile.zip']:
     tftp.readRequest(file)
 for file in ['uploadFile.py', 'uploadFile.docx', 'uploadFile.txt', 'uploadFile.zip']:
     tftp.writeRequest(file)

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2. struct 模块