# ftp server端
import socket, os, time
 
server = socket.socket()
server.bind(("localhost", 8080))
server.listen()
while True:
  conn, addr = server.accept()
  print("连接到客户端:", addr)
  while True:
    try: # windows会直接报错,需要捕获异常
      data = conn.recv(1024)
      if not data:
        print("客户端已断开")
        break
    except Exception as e:
      print("客户端已经断开")
      break
    cmd, filename = data.decode().split() # ex: get name.txt
    if os.path.isfile(filename):
      f = open(filename, "rb")
      # 获取文件的字节大小
      size = os.stat(filename).st_size
      conn.send(str(size).encode()) # 发送文件大小
      conn.recv(1024)
      for line in f:  # 客户端确认后发送文件内容
        conn.send(line)
      f.close()
      print("文件下载完成")
    conn.send("not file".encode())
server.close()

import socket
 
client = socket.socket()
client.connect(("localhost", 8080))
while True:
  cmd = input(":").strip()
  if len(cmd)==0: continue
  if cmd.startswith("get"):
    client.send(cmd.encode()) # 发送请求
    server_response = client.recv(1024)
    if server_response.decode().startswith("not"):
      print("请输入有效文件名")
      continue
    client.send(b"ready to recv file") # 发送确认
    file_size = int(server_response.decode()) # 获取文件大小
    rece_size=0
    filename = cmd.split()[1]
    f = open(filename + ".new", "wb")
    while rece_size < file_size:
      if file_size - rece_size > 1024: # 要收不止一次
        size = 1024
      else: # 最后一次了，剩多少收多少,防止之后发送数据粘包
        size = file_size - rece_size
        print("last receive:", size)
      recv_data = client.recv(size)
      rece_size += len(recv_data) # 累加接受数据大小
      f.write(recv_data) # 写入文件,即下载
    else:
      print("文件下载完成")
      f.close()
client.close()