iOS 12 Network Framework UDP Client Example

UDPClient.swift

import Network
import Foundation

class UDPClient {
    
    var connection: NWConnection
    var address: NWEndpoint.Host
    var port: NWEndpoint.Port
    
    init?(address newAddress: String, port newPort: Int32) {
        guard let codedAddress = IPv4Address(newAddress),
            let codedPort = NWEndpoint.Port(rawValue: NWEndpoint.Port.RawValue(newPort)) else {
                print("Failed to create connection address")
                return nil
        }
        self.address = .ipv4(codedAddress)
        self.port = codedPort
        self.connection = NWConnection(host: .ipv4(codedAddress), port: codedPort, using: .udp)
    }
    
    func connect() {
        connection.stateUpdateHandler = self.stateChanged(newState:)
        connection.start(queue: .global())
    }
    
    func stateChanged(newState: NWConnection.State) {
        print(#function)
        switch (newState) {
            case .ready:
                print("State: Ready\n")
                self.receiveUDP()
            case .setup:
                print("State: Setup\n")
            case .cancelled:
                print("State: Cancelled\n")
            case .preparing:
                print("State: Preparing\n")
            default:
                print("ERROR! State not defined!\n")
        }
    }
    
    func sendUDP(_ content: String) {
        let contentToSendUDP = content.data(using: String.Encoding.utf8)
        self.connection.send(content: contentToSendUDP, completion: NWConnection.SendCompletion.contentProcessed(({ (NWError) in
            if (NWError == nil) {
                print("Data was sent to UDP")
            } else {
                print("ERROR! Error when data (Type: Data) sending. NWError: \n \(NWError!)")
            }
        })))
    }
    
    func receiveUDP() {
        while self.connection.state == .ready {
            self.connection.receiveMessage { (data, context, isComplete, error) in
                if (isComplete) {
                    print("Receive is complete")
                    if (data != nil) {
                        let backToString = String(decoding: data!, as: UTF8.self)
                        print("Received message: \(backToString)")
                    } else {
                        print("Data == nil")
                    }
                }
            }
        }
    }
}