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How does a computer get the list of WiFi? Does it broadcast something and the routers send back something? So what exactly do they send each other? Could I set up my computer to be a wireless router and that is findable on the list of WiFi, without simply linking it to the internet, but doing code for all of the authentication and sending? How?

  • @Akina What is an example of the special software? – Aphrodite Aug 12 at 9:58
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How does a computer get the list of WiFi? Does it broadcast something and the routers send back something? So what exactly do they send each other?

Clients can send "probe request" frames requesting APs to respond, which can be either broadcast to all APs, or carry a list of specific SSIDs that should reply.

Additionally, access points periodically broadcast "beacon" frames containing their SSIDs, usually every 0.1s. This is useful on certain limited-use channels where the client is not allowed to transmit first.

So in order to find all available networks, the client needs to go through all possible Wi-Fi channels (radio frequencies), send probe requests, and collect probe responses and beacons that it receives.

The full details are in the IEEE 802.11 standard, which can be downloaded for free.

A STA shall operate in either a Passive Scanning mode or an Active Scanning mode depending on the current value of the ScanMode parameter […]

To become a member of a particular ESS using passive scanning, a STA shall scan for Beacon and DMG Beacon frames containing that ESS’s SSID, returning all Beacon and DMG Beacon frames matching the desired SSID in the BSSDescriptionSet parameter […]

To actively scan, the STA shall transmit Probe Request frames containing the desired SSID or one or more SSID List elements […] When the SSID List element is present in the Probe Request frame, one or more of the SSID elements may include a wildcard SSID […]


Could I set up my computer to be a wireless router and that is findable on the list of WiFi, without simply linking it to the internet, but doing code for all of the authentication and sending?

Being a Wi-Fi access point has nothing to do with having an Internet connection. (The word 'router' in wireless routers is about network connection, not about Wi-Fi.)

So yes, as long as your computer's Wi-Fi hardware allows choosing this mode, you can configure it to be an access point. Windows 10 has this feature built-in as "hotspot mode"; on Linux you would need to use hostapd.

(There seem to be two methods for creating an AP using a PC Wi-Fi adapter. Many older adapters just support being put in regular access-point mode, but this varies between manufacturers. Some adapters don't support AP mode directly, but do support "Wi-Fi Direct" and it seems that Windows is able to use this as well in order to convince the adapter to act as an AP.)

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