import socket
def main():
  #creat:
  download_client=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
  #link:
  serv_ip=input("please input server IP")
  serv_port=int(input(("please input server port")))
  serv_addr=(serv_ip,serv_port)
  download_client.connect(serv_addr)
  #send and receive
  filename=input("please input filename")
  download_client.send(filename.encode("utf-8"))
  download_data=download_client.recv(1024)
  if download_data:
    with open("receive_"+filename,"wb") as f:
      f.write(download_data)
  download_client.close()
if __name__ == '__main__':
  main()

import socket
def send_data(server_socket):
  while True:
    filename = server_socket.recv(1024).decode("utf-8")
    print("用户请求下载对象是%s"%filename)
    if filename:
      with open(filename, "rb") as f:
        file_data = f.read()
        server_socket.send(file_data)
    else:
      server_socket.close()
      break
def main():
  #creat
  server=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
  #bind
  server.bind(("",4399))
  #listen
  server.listen(128)
  #accept
  while True:
    print("waiting for quest")
    server_socket,client_ip=server.accept()
    print("connected")
    send_data(server_socket)
  #close
  server.close()
if __name__ == '__main__':
  main()