server：
===========================================
import socket
import struct
import json
sk = socket.socket()
sk.bind(('127.0.0.1',8989))
sk.listen()

conn,addr = sk.accept()

resv_size = conn.recv(4)                #会儿收到报头的大小，经过struct转码的字节码
dic_size = struct.unpack('i',resv_size)[0] # 对字节码转码，得到报头的大小
bytes_head = conn.recv(dic_size)               # 接收bytes类型的报头
head = json.loads(bytes_head.decode('utf-8'))    # 真正的报头
filesize = head['filesize']             # 传输文件大小
buffer = 1024
with open(head['filename'],'wb') as f:
    while True:
        if filesize >= buffer:
            content = conn.recv(buffer)
               # 打开文件，写入本地
            f.write(content)
            filesize -= buffer
        else:
            content = conn.recv(filesize)
              # 打开文件，写入本地
            f.write(content)
            break
conn.close()
sk.close()

===============================================================================
client
==================================================================

import socket
import os
import struct
import json
sk = socket.socket()
sk.connect(('127.0.0.1',8989))
dic = {'filepath':r'E:\常用软件\pandownload\pan下载数据\day32',
       'filesize':None,
       'filename':'04 python fullstack s9day32 struct模块补充.mp4'}
path = os.path.join(dic['filepath'],dic['filename'])
dic_size = os.path.getsize(path)
dic['filesize'] = dic_size
dic_json = json.dumps(dic)              #字典转成字符串
# print(dic['filesize'])
bytes_head = dic_json.encode('utf-8')
send_size = struct.pack('i',len(bytes_head))
sk.send(send_size)
sk.send(bytes_head)
buffer = 1024
with open(path,'rb') as f:
    while dic_size:
        if dic_size >= buffer:
            content = f.read(buffer)
            sk.send(content)
            dic_size -= buffer
        else:
            content = f.read(dic_size)
            sk.send(content)

            break

sk.close()