A loop to continuously collect the Wifi strength of nearby access points

Question

Assume I have an iPhone connected to a wifi network with 3+ access points.

I'd like to collect all possible fields around wifi access strength/signal/etc from EACH access point and use that to triangulate, even while in background.

while true {
   ...
   for access_point in access_points {
      ...
      signal_strength = ...
   }
}

I've been reading previous SO answers and other posts, and seems like it wasn't allowed on iOS without a jailbreak for a while, but is now availiable again.

Anyone can show a code snippet of how I'd go about doing this? All new to iOS development..

wow, this has been downvoted by a user who in previous comments has been advertising their own company's framework to do this... — lollercoaster, Jan 27 '17 at 23:42
Possible duplicate of [iPhone get a list of all SSIDs without private library](https://stackoverflow.com/questions/9684341/iphone-get-a-list-of-all-ssids-without-private-library) — Senseful, Sep 24 '18 at 05:25

score 2 · Answer 1 · edited May 23 '17 at 12:25

I've answered how to ping ALL wifi networks in this question;

 func getInterfaces() -> Bool {
    guard let unwrappedCFArrayInterfaces = CNCopySupportedInterfaces() else {
        print("this must be a simulator, no interfaces found")
        return false
    }
    guard let swiftInterfaces = (unwrappedCFArrayInterfaces as NSArray) as? [String] else {
        print("System error: did not come back as array of Strings")
        return false
    }
    for interface in swiftInterfaces {
        print("Looking up SSID info for \(interface)") // en0
        guard let unwrappedCFDictionaryForInterface = CNCopyCurrentNetworkInfo(interface) else {
            print("System error: \(interface) has no information")
            return false
        }
        guard let SSIDDict = (unwrappedCFDictionaryForInterface as NSDictionary) as? [String: AnyObject] else {
            print("System error: interface information is not a string-keyed dictionary")
            return false
        }
        for d in SSIDDict.keys {
            print("\(d): \(SSIDDict[d]!)")
        }
    }
    return true
}

You may have seen this feature in jailbroken apps as it is possible to do this using private libraries, which means that apps that are sold on the iOS store can't be sold if they utilise them.

which part of the iOS do you have to leverage to do this (but isn't allowed)? what is it called? also what bits of information do you get in `SSIDDict `? — lollercoaster, Feb 08 '17 at 16:58
also I don't want the strength of wifi networks, I want the strength of access points (routers)... — lollercoaster, Feb 08 '17 at 16:58

score 2 · Accepted Answer · answered Feb 09 '17 at 14:32

It's been quite a while since I worked with this, so I did a quick check again and now I am fairly certain you misunderstood something you've read. As far as I can tell, Apple did not suddenly revert their previous decision to restrict the public frameworks to scan for access points, i.e. specific MAC addresses and their signal strength.

You can query the specific rssi (signal strength) for a network (i.e. for an ssid), but not for individual MAC addresses. Before iOS 5 you could do that using private APIs, then you could do it with private APIs on a jailbroken device and that's pretty much it.

I don't have the code of my own, old stuff at hand (I used to do this for indoor location tracking before we switched to use iBeacons), so I can't provide you with a sample snippet myself. My code is dated and no longer functioning anyways, but you might find something here.

I would be really interested in the sources you mention that claim iOS 10 now allows this again. Apple closed this for privacy considerations (officially at least, and although this might be true in part it also means developers dealing with location-tracking now need to rely fully on Apple's framework for that only), so I highly doubt they went back on it.

Also, note that this is for sure not something trivial, especially if you're new to iOS development. I haven't even tackled the background idea, you can safely forget about that, because no matter what you do, you will not have a scanner that runs continuously in the background. That's against a very core principle of iOS programming.

A loop to continuously collect the Wifi strength of nearby access points

2 Answers2