AppDelegate.swift

//
//  AppDelegate.swift
//  UDPTest
//
//  Created by Paul Wilkinson on 22/10/19.
//  Copyright © 2019 Paul Wilkinson. All rights reserved.
//

import Cocoa
import SwiftUI

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate {

	var window: NSWindow!
	
	var network: UDPNetwork!


	func applicationDidFinishLaunching(_ aNotification: Notification) {
		// Create the SwiftUI view that provides the window contents.
		let contentView = ContentView()

		// Create the window and set the content view. 
		window = NSWindow(
		    contentRect: NSRect(x: 0, y: 0, width: 480, height: 300),
		    styleMask: [.titled, .closable, .miniaturizable, .resizable, .fullSizeContentView],
		    backing: .buffered, defer: false)
		window.center()
		window.setFrameAutosaveName("Main Window")
		window.contentView = NSHostingView(rootView: contentView)
		window.makeKeyAndOrderFront(nil)
		
		self.network = UDPNetwork(host: "127.0.0.1", port:"4210")!
		self.network.connect()
	}



}

UDPNetwork.swift

//
//  UDPNetwork.swift
//  UDPTest
//
//  Created by Paul Wilkinson on 22/10/19.
//  Copyright © 2019 Paul Wilkinson. All rights reserved.
//

import Foundation
import Network

class UDPNetwork {
	
	var hostUDP: NWEndpoint.Host
	var portUDP: NWEndpoint.Port
	
	private var connection: NWConnection?
	
	private var queue = DispatchQueue(label: "NetworkQuue", qos: .utility)
	
	init?(host: String, port: String) {
		
		guard !host.isEmpty, let portUDP = NWEndpoint.Port(port) else {
			return nil
		}
		
		self.hostUDP = NWEndpoint.Host(host)
		self.portUDP = portUDP
	}
	
	
	func connect()
	{
		connection = NWConnection(host: hostUDP, port: portUDP, using: .udp)
		connection?.stateUpdateHandler =
			{
				(newState) in switch (newState)
				{
				case .ready:
					//The connection is established and ready to send and recieve data.
					print("ready")
					self.sendPaket("Hello")
					self.receive()
				case .setup:
					//The connection has been initialized but not started
					print("setup")
				case .cancelled:
					//The connection has been cancelled
					print("cancelled")
				case .preparing:
					//The connection in the process of being established
					print("Preparing")
				default:
					//The connection has disconnected or encountered an error
					print("waiting or failed")
				}
		}
		connection?.start(queue: self.queue)
	}
	
	func sendPaket(_ packet:String)
	{
		let packetData = packet.data(using: .utf8)
		self.connection?.send(content: packetData, completion: NWConnection.SendCompletion.contentProcessed(({ (error) in
			if let err = error {
				print("Sending error \(err)")
			} else {
				print("Sent successfully")
			}
		})))
		
	}
	
	func receive()
	{
		self.connection?.receiveMessage(completion:
			{
				(data, context, isComplete, error) in
				print("Got it")
				if let err = error {
					print("Recieve error: \(err)")
				}
				
				if let rcvData = data,
					let str = String(data:rcvData, encoding: .utf8) {
					print("Received: \(str)")
				}
				
				self.receive()
				
		})
	}
	
}