Document processing client

import socket,struct,json,os
DOWNLOAD_DIR=r'D:\python13期\网络编程\文件处理\DOWNLOAD'
class FtpClient:
    def __init__(self,host,port):
        self.host=host
        self.port=port
        self.client=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
        self.client.connect((self.host,self.port))
    def interactive(self):
        while True:
            data=input('>>:').strip()
            if not data:continue
            params=data.split()
            cmd=params[0]
            if hasattr(self,cmd):
                func=getattr(self,cmd)
                func(params)
    def get(self,params):
        params_json=json.dumps(params)
        self.client.send(params_json.encode('utf-8'))
        headers_size = struct.unpack('i', self.client.recv(4))[0]
        headers_bytes = self.client.recv(headers_size)
        headers_json = headers_bytes.decode('utf-8')
        headers_dic = json.loads(headers_json)
        print('>>:', headers_dic)
        filename=headers_dic['filename']
        filesize=headers_dic['file_size']
        filepath=os.path.join(DOWNLOAD_DIR,filename)
        with open(filepath,'wb')as f:
            recv_size = 0
            while recv_size < filesize:
                line=self.client.recv(1024)
                recv_size += len(line)
                f.write(line)
            print('>>:下载成功')
if __name__ == '__main__':
    client=FtpClient('127.1.2.3',8999)
    client.interactive()