我可以检查连接到wifi网络的用户（或手机）数量吗

Question

I have read these Getting Started with WiFi on Android . Implemented Marakana's tutorial for basic wifi functionalities.

But my question is: Is there a way to find the number of users connected to a wifi network?

If it can be done, kindly share a link or resources.

If it cant be done, kindly provide some detail, why not?

Thank you,

Answer 1

Getting a list of computers on a network is inherently an unreliable proposition, wifi or wired.

There are three common approaches: a discovery protocol, scanning, and passive listening.

Discovery protocols (such as LLDP from the UPnP framework) work very well for devices that support them. Occasionally also for devices that don't. They don't work at all if firewalls block them, or if switches or wifi access points are configured not to allow traffic between devices.

Scanning means, sending a probe (such as a ping) to each possible IP address. This is something many intrusion detection devices block, and many wifi access points will also prevent you from sending a ping to another device. Also, scanning is entirely unfeasible in IPv6 because each network has billions of IP addresses to probe, rather than the usual 254 in IPv4.

Passive listening means, simply paying attention to the layer-2 traffic on the network, and building a table of MAC addresses based on the ARP traffic (or all traffic). That only works reliably if you have a wired network with a hub - switches don't forward all layer 2 traffic everywhere (although the ARP messages you need most are usually broadcast and available). WiFi isolation may also prevent you from getting enough layer 2 traffic.