When a Wi-Fi device is switched on, it starts spewing out probe requests to try and find a familiar access point. There are two methods of scanning for active WiFi access points. E.g., I have to go to a business meeting this coming week. I'm writing a Python module for finding nearby WiFi client devices. Putting it together. The problem I'm having is that I'm completely reliant on the device broadcasting a probe request for me to discover it. When you don't know the password to a Wi-Fi network at a friend's house or coffee shop, you have to ask for it to save cellular data on your iPhone. All my current scanner does is listen for Probe Requests and logs the clients MAC address. If the hotspot's owner can actually remember the password, good luck putting it in on the first try. What are Wifi probe requests? This program just listen for those "probe requests" and prints to serial port the information. What are Wi-Fi probe requests?¶ Probe requests are sent by a station to elicit information about access points, in particular to determine if an access point is present or not in the nearby environment. For example, does the phone probe once or several times per “probe burst”, how many milliseconds between the probe requests in a given burst, and so on. This is part of the Wi-Fi specification. Thankfully, this whole process has gotten much easier in newer iOS versions. Every probe request contains the interface's MAC address. Those public packets are named as "probe requests" and are used by smartphones to connect faster to wifi networks than if it waits for the network send a Beacon frame to announce the SSID. Wifi is an interesting protocol when you get into the gritty details. I'm wondering if there is any other way to discover devices. To analyze our captured data, we used Wireshark to filter wireless LAN packets down to just the “probe” requests—the “Marco” part of Wi-Fi’s game of “Marco Polo.” wpa_supplicant will send probe requests containing an explicit ESSID name for each entry that has scan_ssid=1. On each scan, wpa_supplicant will send out probe requests. Basically, the client sends a probe request message and then all access points that receive it respond saying they're there. A tool for sniffing unencrypted wireless probe requests from devices: new in 2.1: Displaying the number of hosts; Logging to SQLite database file As you walk around, the smartphone in your pocket is broadcasting its MAC address for anyone within Wi-Fi range to notice. A probe request is a special message sent by a Wifi client to discover what Wifi access points are within range. I will probably link to the conference center's wi-fi. 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