Esp32 error 400 upload spiffs wav file to web server using http post

the arduino IDE debug

  File name                              Size
=================================================
  recording.wav                        163884 bytes
=================================================

===> Upload FILE to python flask Server
recording.wav
163884
[  9396][D][HTTPClient.cpp:293] beginInternal(): protocol: http, host: 192.168.1.112 port: 5000 url: /upload
[  9558][D][HTTPClient.cpp:574] sendRequest(): request type: 'POST' redirCount: 0

[  9781][D][HTTPClient.cpp:1112] connect():  connected to 192.168.1.112:5000
[ 11065][D][HTTPClient.cpp:1257] handleHeaderResponse(): code: 400
[ 11071][D][HTTPClient.cpp:1260] handleHeaderResponse(): size: 167
[ 11077][D][HTTPClient.cpp:618] sendRequest(): sendRequest code=400

httpResponseCode : 400
Error
[ 11084][D][HTTPClient.cpp:373] disconnect(): still data in buffer (167), clean up.

[ 11094][D][HTTPClient.cpp:380] disconnect(): tcp stop