EchoServer with Network.Framework

EchoServer.swift

//
//  EchoServer.swift
//  CS16
//
//  Created by JK on 2020/01/14.
//  Copyright © 2020 codesquad. All rights reserved.
//

import Foundation
import Network

class EchoServer {
    let networkQueue = DispatchQueue.init(label: "myqueue.codesquad.kr")
    var listener : NWListener

    init?(with port: NWEndpoint.Port) {
        let options = NWProtocolTCP.Options()
        let params = NWParameters.init(tls: .none, tcp: options)
        params.allowLocalEndpointReuse = true
        let binding = try? NWListener(using: params, on: port)
        guard binding != nil else { return nil }
        listener = binding!
    }
    
    func run() {
        setupListener()
    }
 
    private func setupListener() {
        listener.stateUpdateHandler = { newState in
            switch newState {
            case .ready:
                print("Listener ready on \(String(describing: self.listener.port))")
            case .failed(let error):
                print("Listener failed with \(error), restarting")
                self.listener.cancel()
            default:
                break
            }
        }
        listener.newConnectionHandler = setup(connection:)
        listener.start(queue: networkQueue)
    }
    
    private func setup(connection: NWConnection) {
        connection.stateUpdateHandler = { newState in
            switch newState {
            case .ready:
                self.setupReceiver(of: connection)
            case .failed(_):
                connection.cancel()
            case .cancelled:
                print("\(connection) cancelled")
            default:
                break
            }
        }
        connection.start(queue: self.networkQueue)
    }

    private func setupReceiver(of connection: NWConnection) {
        connection.receive(minimumIncompleteLength: 4, maximumLength: 1024) { (content, context, isComplete, error) in
            
            if let data = content, !data.isEmpty {
                connection.send(content: content, completion: .idempotent)
                print("\(connection) received and echo - ", String(data: data, encoding: .utf8)!)
            }
            connection.forceCancel()
            if let error = error {
                print("\(connection) error - ", error.localizedDescription)
            }
        }
    }
}

main.swift

import Foundation
import Network

let server = EchoServer(with: NWEndpoint.Port.init(integerLiteral: 9000))
server?.run()

RunLoop.main.run()