socket模拟服务器，客户端下载东西（ftp）

服务端（ftp_server.py）

 import hashlib,socket,os

 server = socket.socket()
 server.bind(("localhost",9999))
 server.listen()
 while True:
     client,address = server.accept()
     while True:
         req_data = client.recv(1024)
         print(req_data.decode())
         if not req_data:
             print("客户端连接已断开")
             break
         if len(req_data) == 0: continue
         if os.path.isfile(req_data.decode()):
             file_size = os.stat(req_data).st_size
             print("file size:",file_size)
             client.send(str(file_size).encode('utf-8'))
             client_ack = client.recv(1024)
             f = open(req_data,'rb')
             for line in f:
                 m = hashlib.md5()
                 print(line)
                 client.send(line)
                 m.update(line)
             res = m.hexdigest()
             client.send(res.encode('utf-8'))
         else:
             client.send("无此文件")

客户端（ftp_client.py）

 import socket,hashlib

 client = socket.socket()
 client.connect(("localhost",9999))
 while True:
     cmd = input("输入文件名>>:")
     if cmd !=None or cmd != '':
         client.send(cmd.encode('utf-8'))
     file_total_size = client.recv(1024)
     print(file_total_size)
     file_total_size = int(file_total_size)
     client.send(b"ok")
     curent_size = 0
     size = 0
     m = hashlib.md5()
     f = open(cmd+"new",'wb')
     while curent_size != file_total_size:
         if file_total_size-curent_size > 1024:#不是最后一次
             size = 1024
         else:
             size = file_total_size-curent_size
         ser_info = client.recv(size)
         print(ser_info)
         f.write(ser_info)
         m.update(ser_info)
         curent_size += len(ser_info)

     else:
         print("原文件：%s，新文件：%s"%(str(file_total_size),str(curent_size)))
         ser_md5 = client.recv(1024)
         cli_md5 = m.hexdigest()
         f.close()
         print("cli_md5:%s,ser_md5:%s"%(cli_md5,ser_md5.decode()))

说明：

1.程序使用python3运行

2.明确http传输的基本概念