Socket爬虫图片打开提示不支持此格式

环境：python3.7.2

尝试用Socket爬虫网站：http://desk.zol.com.cn/

附代码：

#https://desk-fd.zol-img.com.cn/t_s960x600c5/g5/M00/00/07/ChMkJl3qNKaIDNA2AARqqK0FxbEAAvnJAJbLQMABGrA592.jpg

import socket

b=socket.socket()

b.connect(('desk-fd.zol-img.com.cn',80))

req_line='GET /t_s960x600c5/g5/M00/00/07/ChMkJl3qNKaIDNA2AARqqK0FxbEAAvnJAJbLQMABGrA592.jpg HTTP/1.1\r\n'

req_header='host:desk-fd.zol-img.com.cn\r\nUser-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36\r\nReferer: http://desk.zol.com.cn/bizhi/8376_103845_2.html\r\n'

empty_line='\r\n'

req_content=''

b.send((req_line+req_header+empty_line+req_content).encode())

complete_content=b''

res_content=b.recv(4096)

while res_content:

    complete_content+=res_content

res_content=b.recv(4096)

print(len(res_content))

with open('d:/temp2.jpg','wb')as f:

    f.write(complete_content)

执行结果：正常

问题：图片和网上下载的大小一样，打开提示不支持此格式

用网页下载的图一正常打开