[Original] Protocol conflict submitted by the server

An exception occurred when using httpwebrequest today,
Prompt that the server has submitted the Protocol conflict section = responsestatusline
After packet capture, we found the following interactions:
Post/service. ep http/1.1
Content-Type: Application/X-WWW-form-urlencoded; charset = UTF-8
User-Agent: Mozilla/4.0 (compatible; MSIE 5.00; Windows 98)
HOST: 127.0.0.1: 10900
Content-Length: 393
Secondary CT: 100-continue
Connection: keep-alive

Servic ...... % 3E

================================
Required bytes TTP/1.1 200 OK
Content-Type: text/html; charset = UTF-8
Content-Length: 269
Connection: Close

632836355380156250796096
7a46182a03213ed07bad242e2ff4e696
.....
==============
Note: Too Many TTP/1.1 200 OK. It turns out that the server returned an error. No wonder.
It is estimated that the server uses UTF-8 encoding.
And utf8 returns:Getpreamble() = Byte [] {0xef, 0xbb, 0xbf };