Swift command-line script to find Bonjour services on your local network.

allbonjour.swift

#!/usr/bin/swift

// Swift script to search for Bonjour services on the local network.
// Found services are printed to the console.

import Foundation
import CoreFoundation

// Inner search, finds services of a particular type

class ServicesDiscoverer : NSObject, NSNetServiceBrowserDelegate {
    let browser = NSNetServiceBrowser()
    let service: NSNetService
    let allServicesDiscoverer: AllServicesDiscoverer
    
    // Save the list of services until we have them all before printing
    var serviceNames = Array<String>()
    
    init(service: NSNetService, allServicesDiscoverer: AllServicesDiscoverer) {
    	self.service = service
    	self.allServicesDiscoverer = allServicesDiscoverer
	    super.init()
        browser.delegate = self
    }

	func start() {
        let parts = service.type.componentsSeparatedByString(".")
        let type = "\(service.name).\(parts[0])."
        browser.searchForServicesOfType(type, inDomain: "local.")
    }

    func netServiceBrowser(browser: NSNetServiceBrowser, didNotSearch errorDict: [String : NSNumber]) {
		self.allServicesDiscoverer.removeDiscoverer(self);
    }
    
	func netServiceBrowserDidStopSearch(browser: NSNetServiceBrowser) {
		self.allServicesDiscoverer.removeDiscoverer(self);
	}

    func netServiceBrowser(browser: NSNetServiceBrowser, didFindService service: NSNetService, moreComing: Bool) {
	    serviceNames.append(service.name)
	    if (!moreComing) {
	    	NSOperationQueue.mainQueue().addOperationWithBlock {
				for name in self.serviceNames {
					print("\(self.service.name) \(self.service.type) \"\(name)\"")
				}
				print("")
				
				self.allServicesDiscoverer.removeDiscoverer(self);
			}
	    }
    }
}

// Outer search, searches for all the types of services available, and uses
// ServicesDiscoverer to search for instances of those services.

class AllServicesDiscoverer : NSObject, NSNetServiceBrowserDelegate, NSNetServiceDelegate {
    
    let browser = NSNetServiceBrowser()
    var serviceDiscoverers = Set<ServicesDiscoverer>()
    var searchComplete = false
    
    func start() {
        browser.delegate = self
        browser.searchForServicesOfType("_services._dns-sd._udp.", inDomain: "local.")
    }
    
    func removeDiscoverer(discoverer: ServicesDiscoverer) {
    	serviceDiscoverers.remove(discoverer)

    	if (searchComplete && serviceDiscoverers.isEmpty) {
	    	exit(0)
	    }
    }
    
    func netServiceBrowser(browser: NSNetServiceBrowser, didFindService service: NSNetService, moreComing: Bool) {
		let serviceDiscoverer = ServicesDiscoverer(service:service, allServicesDiscoverer: self)        
        serviceDiscoverers.insert(serviceDiscoverer)
        serviceDiscoverer.start()
        
        if (!moreComing) {
	        searchComplete = true
	    }
    }
}

// Start the search
let serviceDiscoverer = AllServicesDiscoverer()
serviceDiscoverer.start()

// The search is asynchronous, so run the run loop and let the end of the search exit the process.

NSRunLoop.currentRunLoop().run()

Updated to Swift 5:

class ServicesDiscoverer : NSObject, NetServiceBrowserDelegate {
    let browser = NetServiceBrowser()
    let service: NetService
    let allServicesDiscoverer: AllServicesDiscoverer
    
    // Save the list of services until we have them all before printing
    var serviceNames = Array<String>()
    
    init(service: NetService, allServicesDiscoverer: AllServicesDiscoverer) {
        self.service = service
        self.allServicesDiscoverer = allServicesDiscoverer
        super.init()
        browser.delegate = self
    }

    func start() {
        let parts = service.type.components(separatedBy: ".")
        let type = "\(service.name).\(parts[0])."
        browser.searchForServices(ofType: type, inDomain: "local.")
    }

    func netServiceBrowser(_ browser: NetServiceBrowser, didNotSearch errorDict: [String : NSNumber]) {
        self.allServicesDiscoverer.removeDiscoverer(discoverer: self);
    }
    
    func netServiceBrowserDidStopSearch(_ browser: NetServiceBrowser) {
        self.allServicesDiscoverer.removeDiscoverer(discoverer: self);
    }

    func netServiceBrowser(_ browser: NetServiceBrowser, didFind service: NetService, moreComing: Bool) {
        serviceNames.append(service.name)
        if (!moreComing) {
            OperationQueue.main.addOperation {
                for name in self.serviceNames {
                    print("\(self.service.name) \(self.service.type) \"\(name)\"")
                }
                print("")
                
                self.allServicesDiscoverer.removeDiscoverer(discoverer: self);
            }
        }
    }
}

// Outer search, searches for all the types of services available, and uses
// ServicesDiscoverer to search for instances of those services.
class AllServicesDiscoverer : NSObject, NetServiceBrowserDelegate, NetServiceDelegate {
    
    let browser = NetServiceBrowser()
    var serviceDiscoverers = Set<ServicesDiscoverer>()
    var searchComplete = false
    
    func start() {
        browser.delegate = self
        browser.searchForServices(ofType: "_services._dns-sd._udp.", inDomain: "local.")
    }
    
    func removeDiscoverer(discoverer: ServicesDiscoverer) {
        serviceDiscoverers.remove(discoverer)

        if (searchComplete && serviceDiscoverers.isEmpty) {
            exit(0)
        }
    }
    
    func netServiceBrowser(_ browser: NetServiceBrowser, didFind service: NetService, moreComing: Bool) {
        let serviceDiscoverer = ServicesDiscoverer(service:service, allServicesDiscoverer: self)
        serviceDiscoverers.insert(serviceDiscoverer)
        serviceDiscoverer.start()
        
        if (!moreComing) {
            searchComplete = true
        }
    }
}

 // Start the search
let serviceDiscoverer = AllServicesDiscoverer()
serviceDiscoverer.start()

// The search is asynchronous, so run the run loop and let the end of the search exit the process.
RunLoop.current.run()