
 This value is cached for the duration of the connection after the
 first call to this method.  In other words, only the first time
 that you invoke this method will it issue a SYST command to the
 FTP server.  FTPClient will remember the value and return the
 cached value until a call to disconnect.
 <p></div>
<dl><dt><span class="strong">Returns:</span></dt><dd>The system type name obtained from the server.  null if the
       information could not be obtained.</dd>
<dt><span class="strong">Throws:</span