how can I detect success/failure sftp Batch script on Windows OS?

I use %errorlevel% to detect success/failure, sometime the %errorlevel% be returned by 0, but that session is fail and the file is not upload to the server. my script is below

how can I detect sftp uploaded correctly? THX so much

@echo off
(echo cd %4
  echo put %2
  echo exit)>sftpScript.txt
sftp -b sftpScript.txt %3
set result=%errorlevel%
if result EQU 0 (
  del sftpScript.txt
  del %2
) else (
  del sftpScript.txt
)
exit %result%