According to Wiki:
Only one of the Wi-Fi devices needs to be compliant with Wi-Fi Direct to establish a peer-to-peer connection that transfers data directly between them with greatly reduced setup.
How to actually establish the Wifi Direct connection from one Samsung Android phone (with Wifi Direct enabled) with another Samsung Android phone (without Wifi Direct / with Wifi Direct disabled)?
(FYI, I could establish connection with Wifi Direct enabled on both phones. But theoretically only enabling one phone is enough.)