Wi-Fi Probe request is used to actively seek any, or a particular access point.
For example, if you turn on the Wi-Fi of the smart phone, the smart phone will show all available AP list. At this time, the smart phone transmits the “Probe Request” packets to search the APs around. After then the phone will show a list of APs that sends the response packets to the phone.
The probe request packet includes MAC address information of the device. Therefore, if we can capture this probe request packet in any specific area, it is possible to collect the data about staying time of devices. In this posting, we will make a device to track Wi-Fi devices using probe request packets.
We need below hardware
- WIZwiki-W7500 (ARM Cortex-M0 Platform)
- WizFi310 : Wi-Fi Module (This module has the function to capture the probe-request packet.)
- SD CARD
WizFi310 scans the probe request around and send the data to WIZwiki-W7500ECO. After parsing the data, WIZwiki-W7500 save the data in the SD Card.
The source code for this operation, can be downloadable from mbed.
We could get the below data.
- X4000 : Probe request packet
- xx:xx:xx ~~ : MAC Address
- -84:RSSI (Wireless Signal Sensitivity)
By analyzing above raw data, we could get below result
- WizFi310 captured about 36,000 Probe request packets
- Found 343 MAC addresses
- Captured 15,000 probe requests from a MAC address
- Captured more than 1000 probe requests from 5 MAC addresses
- Captured more than 100 probe requests from 33 address
If we use this ‘probe request packet capture’ function, we may be able to make the device to search the visitors who often visit a specific area and sends various information such as restaurant, movies, parking places and etc.