The 3DS dlplay title has two dlplay modes: 3DS and DS. DS dlplay is just regular dsmode dlplay, same interface and protocol as before. Like DS gamecards, holding down start+select while starting the dsmode dlplay client will disable stretching the screens.
3DS dlplay protocol
3DS dlplay protocol has completely changed since the ds-mode protocol. Cleartext beacons have static Nintendo tag data, broadcasted at a rate of 0.102400/s. WPA2 data frames are broadcasted as well, the size of these varies. After a client authenticates to the host, the host sends an association response, with a random ASCII hex SSID, like: "EB6FAB77". After that the systems communicate and transfer the binary with WPA2 encrypted data frames.
This is a dump of the Nintendo tag of the cleartext beacon from Monkey ball 3D, with vendor 001f32:
000: 18 05 9f ae 17 c8 a5 1d 0b 81 28 be 74 0f d4 af 010: 97 30 04 60 fd 2d f3 d9 8d bc 22 80 51 60 3c 75 020: d9 89 6d 16 c4 f3 aa 89 26 d4 14 25 67 75 8e 4b 030: 3c 97 85 c9 83 15 d4 96 06 b1 29 b6 f5 51 57 71 040: cc b6 1f 4a c8 bd 4f c0 57 43 cb ab fa 37 74 b0 050: 64 6b 87 69 a1 de a4 05 7c 7c 49 5d f5 21 25 83 060: 4c f2 d0 70 38 14 7b 0f f4 97 f7 ff f3 ff 36 cd 070: c2 e2 c0 78 98 d1 d5 4d 3d d4 9b 57 84 6c e2 4f 080: 25 f2 56 c4 19 88 64 13 78 68 e2