ddwtp12

.swift

import UIKit
import Network

class Connect: NSObject {
  
  private var talking: NWConnection?
  private var listening: NWListener?
  
  
  func listenUDP( port: Int) {
    let port2U = NWEndpoint.Port.init(integerLiteral: NWEndpoint.Port.IntegerLiteralType(port))
    do {
      self.listening = try NWListener(using: .udp, on: port2U)
      self.listening?.stateUpdateHandler = {(newState) in
        switch newState {
        case .ready:
          print("ready")
        default:
          break
        }
      }
      self.listening?.newConnectionHandler = {(newConnection) in
        newConnection.stateUpdateHandler = {newState in
          switch newState {
          case .ready:
            print("new connection")
            self.receive(on: newConnection)
          default:
            break
          }
        }
        newConnection.start(queue: DispatchQueue(label: "new client"))
      }
    } catch {
      print("unable to create listener")
    }
    self.listening?.start(queue: .main)
  }
  
  func receive(on connection: NWConnection) {
    connection.receiveMessage { (data, context, isComplete, error) in
      if let error = error {
        print(error)
        return
      }
      if let data = data, !data.isEmpty {
        let backToString = String(decoding: data, as: UTF8.self)
        print("b2S",backToString)
      }
    }
  }
  
}