NetServiceBrowser (Bonjour) - why must stop() be called before searches work?

Hello,

In the documentation for Foundation's NetServiceBrowser (https://developer.apple.com/documentation/foundation/netservicebrowser) it states:

"To use an

NSNetServiceBrowser

schedule(in:forMode:)

remove(from:forMode:)

searchForRegistrationDomains()

searchForBrowsableDomains()

searchForServices(ofType:inDomain:)

However, that's not quite true. There must be a call to the stop() function of the browser before searches work.

e.g. if you place the code below into a Swift Playground you get the error:

Didn't search for service because: ["NSNetServicesErrorDomain": 10, "NSNetServicesErrorCode": -72003]

If you uncomment line 21 then the code works. Why does one have to call stop() on the NetServiceBrowser before searching, and shouldn't the docs mention this?

Thanks.

import Foundation

class DenonFinder: NSObject, NetServiceBrowserDelegate  {
    let browser = NetServiceBrowser()

    func start() {
        browser.delegate = self
        print("Search for registration domains")
        browser.searchForRegistrationDomains()
    }
    
    //MARK: NetServiceBrowserDelegate
    
    func netServiceBrowser(_ browser: NetServiceBrowser, didFindDomain domainString: String, moreComing: Bool) {
        print("didFindDomain: \(domainString)")
        if (moreComing) {
            print("moreComing")
        }

        //  Why must stop be called before search?
//        browser.stop()

        let webService = "_http._tcp."
        print("searchForServices: \(webService) in domain \(domainString)")
        browser.searchForServices(ofType: webService, inDomain: domainString)
    }
    
    func netServiceBrowserWillSearch(_ browser: NetServiceBrowser) {
        print("Search about to begin")
    }
    
    func netService(_ sender: NetService, didNotResolve errorDict: [String : NSNumber]) {
        print("Resolve error:", sender, errorDict)
    }
    
    func netServiceBrowserDidStopSearch(_ browser: NetServiceBrowser) {
        print("Search stopped")
    }

    func netServiceBrowser(_ browser: NetServiceBrowser, didFind service: NetService, moreComing: Bool) {
        print("Service found: \(service)")
        if (moreComing) {
            print("moreComing")
        } else {
            browser.stop()
        }
    }
    
    func netServiceBrowser(_ browser: NetServiceBrowser, didRemove service: NetService, moreComing: Bool) {
        print("Service went away: \(service)")
    }
    
    func netServiceBrowser(_ browser: NetServiceBrowser, didNotSearch errorDict: [String : NSNumber]) {
        print("Didn't search for service because: \(errorDict)")
    }
}




class MainApplication {
    let runLoop = RunLoop.current
    let distantFuture = Date.distantFuture
//    let testTimer = Timer.scheduledTimer(withTimeInterval: 4.0, repeats: false, block: {_ in print("timer fired")})
    let denonFinder = DenonFinder()

    ///    Set this to false when we want to exit the app...
    var shouldKeepRunning = true


    init() {
        denonFinder.start()
    }

    func run() {
        while shouldKeepRunning == true &&
            runLoop.run(mode:.default, before: distantFuture) {}
    }
}

//    Entry Point
let app = MainApplication()
app.run()