JS readFile() does not working in web client

Hi, experts. I have one problem with working readFile() function in JS. I created wizard with which must take file from user and read its as binary, so i use formdesigner element "file", in input i wrote variable $attach. In wizard's Actions tab i wrote this code:

try
{
      var str = readFile(vars.$attach, "B")
}
catch (ex)
{
      print(ex)
}

But it does not work, after click Finish button in wizard there is error: "Unable to open file 45c581da559d78160155bbdbcc020090/1.txt for reading", this error is everywhere except HP Service Manager Client that installed on server there HP Service Manager Server installed.

Have any ideas what is it?

P.S. HP Service Manager Server v9.41.3016