Unfortunately can't say anything regarding Raspberry specific, just some general tips on communication from any outer platform.
- setup direct WiFi connection from Raspberry to OBD2 Device
- check that Raspberry's get (or pre-set) address in the same network 192.168.0.XXX and mask is 255.255.255.0
- setup socket (serial port protocol - SPP) connection from "terminal" with OBD2 device
- first check that OBD2 responds with "internal" AT-commands, for example ATZ - reset the device
- be sure that sent command is finished with "carriage return" (using terminal, that is automatic... just pressing Enter at the end of command)
- if all above is Ok, could proceed with OBD2 commands
Thanks!