如何在iOS、swift中使用UDP套接字？

我正在尝试连接到本地esp8266 UDP服务器。SwiftSocket没有文档。CocoaAsyncSocket不工作。 如何连接和发送数据到udp服务器？我该怎么办

我编写了示例UDP python服务器并尝试通过SwiftSocket和CoCoCoaAsyncSocket连接到它们。我很抱歉没有收到应用程序的反馈。服务器不接收连接。 例如-最重要的尝试之一：

    var connection = NWConnection(host: "255.255.255.255", port: 9093, using: .udp)

    connection.stateUpdateHandler = { (newState) in
        switch (newState) {
        case .ready:
            print("ready")
        case .setup:
            print("setup")
        case .cancelled:
            print("cancelled")
        case .preparing:
            print("Preparing")
        default:
            print("waiting or failed")
            break
        }
    }
    connection.start(queue: .global())
    connection.send(content: "Xyu".data(using: String.Encoding.utf8), completion: NWConnection.SendCompletion.contentProcessed(({ (NWError) in
        print(NWError)
    })))
    connection.receiveMessage { (data, context, isComplete, error) in
        print("Got it")
        print(data)
    }

---

无法连接到服务器

在尝试发送或接收任何数据之前，您需要等待连接处于就绪状态。您还需要在属性中保留对连接的强引用，以防止函数退出后立即释放连接

var connection: NWConnection?

func someFunc() {

    self.connection = NWConnection(host: "255.255.255.255", port: 9093, using: .udp)

    self.connection?.stateUpdateHandler = { (newState) in
        switch (newState) {
        case .ready:
            print("ready")
            self.send()
            self.receive()
        case .setup:
            print("setup")
        case .cancelled:
            print("cancelled")
        case .preparing:
            print("Preparing")
        default:
            print("waiting or failed")

        }
    }
    self.connection?.start(queue: .global())

}

func send() {
    self.connection?.send(content: "Test message".data(using: String.Encoding.utf8), completion: NWConnection.SendCompletion.contentProcessed(({ (NWError) in
        print(NWError)
    })))
}

func receive() {
    self.connection?.receiveMessage { (data, context, isComplete, error) in
        print("Got it")
        print(data)
    }
}

---

这个解决方案对我有用！谢谢@Paulw11
Swift 4、XCode 10.1、iOS 12.0
简单连接到公共UDP服务器（这不是最佳版本，但有效）：

导入UIKit
导入网络
类ViewController:UIViewController{
var连接：NWConnection？
var hostUDP:NWEndpoint.Host=“iperf.volia.net”
var portUDP:NWEndpoint.Port=5201
重写func viewDidLoad（）{
super.viewDidLoad（）
//黑客等待，直到一切都设置好
变量x=0
当我在空项目上运行此代码时（从viewDidLoad（）运行someFunction（）），我得到以下错误：2019-02-12 22:28:41.553015+0300 Nanopix Pilot[3891:189405][]nw_套接字_服务_写入_块_调用[C1:1]sendmsg（fd 5，3字节）[13:权限被拒绝]您正在尝试发送广播数据包；我不确定这是否允许。最好将数据包发送到您尝试与之通信的特定主机。非常感谢！我已成功连接到公共UDP服务器。下面我将编写最终代码，尝试在swift 5.x iOS 13上实现此功能。发送数据没有问题，但我似乎无法完成为了让它接收任何信息。我正在尝试使用python脚本发送一条简单的消息。你救了我的命！最终我能够使用Swift 5打开连接并向服务器发送消息，而无需将我的macOS升级到Catalina！谢谢！P.S:如果你需要使用TCP进行连接，也可以使用此示例，只需更改为UDP即可到TCP。如何使连接持续侦听？
import UIKit
import Network

class ViewController: UIViewController {

    var connection: NWConnection?
    var hostUDP: NWEndpoint.Host = "iperf.volia.net"
    var portUDP: NWEndpoint.Port = 5201

    override func viewDidLoad() {
        super.viewDidLoad()

        // Hack to wait until everything is set up
        var x = 0
        while(x<1000000000) {
            x+=1
        }
        connectToUDP(hostUDP,portUDP)
    }

    func connectToUDP(_ hostUDP: NWEndpoint.Host, _ portUDP: NWEndpoint.Port) {
        // Transmited message:
        let messageToUDP = "Test message"

        self.connection = NWConnection(host: hostUDP, port: portUDP, using: .udp)

        self.connection?.stateUpdateHandler = { (newState) in
            print("This is stateUpdateHandler:")
            switch (newState) {
                case .ready:
                    print("State: Ready\n")
                    self.sendUDP(messageToUDP)
                    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")
            }
        }

        self.connection?.start(queue: .global())
    }

    func sendUDP(_ content: Data) {
        self.connection?.send(content: content, 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 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() {
        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")
                }
            }
        }
    }
}