Use wifi direct at 2.4GHz on Galaxy Tab S2

It is strange that you are trying to use wi-fi direct to accomplish this task. AFAIK most Wi-Fi Direct compatible devices use the 2.4GHz connection (by default) and given that most devices nowadays only communicate with other Wi-Fi Direct-certified devices not just random.

I suggest you simply use a standard wi-fi connection i.e something like a mobile hotspot using your device or PC as host. If it is a case that your mobile predominantly uses 5GHz connection, then you can use this to force a 2GHz connection.

Another option apart from WebDAV server is using an SMB, FTP server or even TCP server of your folder structure in sdcard or internal storage similar to this.