在JavaFx中编码UDP通信

我在JavaFx中编码UDP通信时遇到问题。

代码能够发送消息但不能接收消息。

我应该在源代码中修改以接收消息？

这是源代码：

public class JavaFXApplication10 extends Application { public DatagramSocket receivesocket; public DatagramPacket receivepacket; public DatagramSocket sendsocket; public DatagramPacket sendpacket; public InetSocketAddress remoteAdress; public Label label_IP; public TextField tx_IP; public Label label_SENDPORT; public Label label_RECEIVEPORT; public TextField tx_SENDPORT; public TextField tx_RECEIVEPORT; public Button bt_co; public Button bt_start ; private String message; private XYChart.Series series; private Timeline timer; private static String IP = "192.168.121.23"; private static Integer SENDPORT = 12345; private static Integer RECEIVEPORT = 12345; public double time_counter=0.0; private String text; private byte[] b; @Override public void start(Stage stage) throws Exception{ /* text */ tx_IP = TextFieldBuilder.create().text(IP).build(); /* text */ tx_SENDPORT = TextFieldBuilder.create().text(""+SENDPORT).build(); /* text */ tx_RECEIVEPORT = TextFieldBuilder.create().text(""+RECEIVEPORT).build(); /*button */ bt_co = ButtonBuilder.create().text("Connection") .prefWidth(200) .alignment(Pos.CENTER) .id("connect") .build(); /* button_start */ bt_start = ButtonBuilder.create().text("START") .id("start") .build(); /* timer */ timer = new Timeline(new KeyFrame(Duration.millis(1000), new EventHandler(){ @Override public void handle(ActionEvent event) { time_counter = time_counter+1; // time } })); timer.setCycleCount(Timeline.INDEFINITE); timer.play(); /*figure*/ stage.setTitle("Line Chart Sample"); final NumberAxis xAxis = new NumberAxis(); final NumberAxis yAxis = new NumberAxis(); xAxis.setLabel("Time [s]"); yAxis.setLabel("Force [N]"); //creating the chart final LineChart lineChart = new LineChart(xAxis,yAxis); lineChart.setTitle(""); //defining a series series = new XYChart.Series(); series.setName("Force"); series.getData().add(new XYChart.Data(0.0,0.0)); lineChart.getData().add(series); HBox root1 = HBoxBuilder.create().spacing(100).children(tx_IP ,tx_SENDPORT,tx_RECEIVEPORT).build(); HBox root2 = HBoxBuilder.create().spacing(50).children(bt_co).build(); HBox root3 = HBoxBuilder.create().spacing(25).children(bt_start).build(); VBox root4 = VBoxBuilder.create().spacing(25).children(root1,root2,root3,lineChart).build(); Scene scene = new Scene(root4); recieve_UDP(); scene.addEventHandler(ActionEvent.ACTION,actionHandler); stage = StageBuilder.create().width(640).height(640).scene(scene).title(" ").build(); stage.show(); } private void recieve_UDP() throws SocketException, IOException { ScheduledService ss = new ScheduledService() { @Override protected Task createTask() { Task task = new Task() { @Override protected Boolean call() throws Exception { receivesocket = null; byte[] receiveBuffer = new byte[1024]; receivepacket = new DatagramPacket(receiveBuffer, receiveBuffer.length); receivesocket = new DatagramSocket(RECEIVEPORT); receivesocket.receive(receivepacket); message = new String(receivepacket.getData(),0, receivepacket.getLength()); System.out.println(message); receivesocket.close(); return true; }; }; return task; } }; ss.start(); } EventHandler actionHandler = new EventHandler(){ public void handle (ActionEvent e){ ////////////////////////////////////////////////////////////////////////////// Button src =(Button)e.getTarget(); text = src.getId(); System.out.println(text); b = new byte[5]; if(text == "connect"){ String text_IP = tx_IP.getText(); label_IP.setText(text_IP); IP = text_IP; String text_SENDPORT = tx_SENDPORT.getText(); label_SENDPORT.setText(text_SENDPORT); SENDPORT = Integer.parseInt( text_SENDPORT); String text_RECEIVEPORT = tx_RECEIVEPORT.getText(); label_RECEIVEPORT.setText(text_RECEIVEPORT); RECEIVEPORT = Integer.parseInt(text_RECEIVEPORT); } else{ remoteAdress = new InetSocketAddress(IP, SENDPORT); sendsocket = null; try { sendsocket = new DatagramSocket(); } catch (SocketException ex) { Logger.getLogger(JavaFXApplication10.class.getName()).log(Level.SEVERE, null, ex); } } if(text=="start"){ b[0] = (byte)0x02; text ="OK"; } else{ } Send_UDP(); /////////////////////////////////////////////////////// } }; public void Send_UDP(){ /////////////////////////////////////////////////////// if(text=="OK"){ sendpacket = new DatagramPacket(b, b.length,remoteAdress); try { sendsocket.send(sendpacket); } catch (IOException ex) { Logger.getLogger(JavaFXApplication10.class.getName()).log(Level.SEVERE, null, ex); } sendsocket.close(); text=""; } else {} /////////////////////////////////////////////////////// } public static void main(String[] args) { launch(args); } } 

Answer 1

您的代码非常模糊，也许我不明白所有这些代码块的目的，但我可以告诉您UDP通信非常简单，让我先介绍一下UDP通信的工作方式：

UDP通信复习

请注意，我仅使用下面的一些代码片段进行演示，所以请不要看完整性，完整的代码可以在我最后粘贴的代码中找到。

• UDP可用于单播和多播通信。 如果UDP用于单播通信，那么将始终有UDP客户端从UDP服务器请求某些内容，但是如果UDP用于多播通信，则UDP服务器将多播/广播该消息到所有侦听UDP客户端。

• （ 我现在将详细讨论UDP单播 ）UDP服务器将在网络端口上侦听客户端请求DatagramSocket socket = new DatagramSocket(8002); socket.receive(packet); DatagramSocket socket = new DatagramSocket(8002); socket.receive(packet);

• UDP客户端希望与UDP服务器通信，因此它打开DatagramSocket并通过它发送DatagramPacket 。 DatagramPacket将包含UDP服务器的端点。

• UDP客户端使用socket.send(packet);发送消息后socket.send(packet); 然后，它将使用socket.receive(packet);准备从UDP服务器接收响应socket.receive(packet); （ 我认为这是你失踪的地方 ） 最重要的是要明白，如果客户端没有准备接收那么它将无法获得UDP服务器将发送的内容，因为在UDP的情况下，UDP客户端和UDP服务器，因此UDP必须在发送消息后进行侦听 。
• UDP服务器将从UDP客户端接收请求，将处理请求并将使用sendingDatagramSocket.send(packet);发送sendingDatagramSocket.send(packet); 。 它将使用UDP客户端的响应和端点准备DatagramPacket 。
• 正在监听的UDP客户端，如上面提到的步骤socket.receive(packet); 将从UDP服务器获得响应。 这里需要注意的重要一点是，如果UDP客户端没有监听或者没有在发出请求时打开它所打开的同一端口（基本上使用相同的DatagramSocket对象来发送请求），那么UDP客户端永远不会收到任何UDP服务器要发送 。

回答OP的问题

主要问题是在Send_UDP你只发送但没有收到，而在recieve_UDP你只收到但不发送。

所以，基本上你需要在UDP客户端和UDP服务器中发送和接收 ，它只是反之亦然，但你需要做两件事。

示例UDP服务器和UDP客户端

UDP客户端：

 import java.io.IOException; import java.net.DatagramPacket; import java.net.DatagramSocket; import java.net.InetAddress; import java.util.Date; public class SimpleUDPClient { public static void main(String[] args) throws IOException { // get a datagram socket DatagramSocket socket = new DatagramSocket(); System.out.println("### socket.getLocalPort():" + socket.getLocalPort() + " | socket.getPort(): " + socket.getPort()); // send request byte[] buf = "Hello, I am UDP client".getBytes(); InetAddress address = InetAddress.getByName("localhost"); DatagramPacket packet = new DatagramPacket(buf, buf.length, address, 8002); socket.send(packet); // get response packet = new DatagramPacket(buf, buf.length); System.out.println("Waiting to receive response from server." + new Date()); socket.receive(packet); System.out.println("Got the response back from server." + new Date()); // display response String received = new String(packet.getData()); System.out.println("Quote of the Moment: " + received); socket.close(); } } 

UDP服务器：

 import java.io.*; import java.net.*; import java.util.*; public class SimpleUDPServer { public static void main(String[] args) throws SocketException, InterruptedException { DatagramSocket socket = new DatagramSocket(8002); while (true) { try { byte[] buf = new byte[256]; // receive request DatagramPacket packet = new DatagramPacket(buf, buf.length); socket.receive(packet); System.out.println("### socket.getLocalPort():" + socket.getLocalPort() + " | socket.getPort(): " + socket.getPort()); // figure out response String dString = "Server is responding: asd asdd"; buf = new byte[256]; buf = dString.getBytes(); // send the response to the client at "address" and "port" InetAddress address = packet.getAddress(); int port = packet.getPort(); System.out.println("Data from client: " + new String(packet.getData())); packet = new DatagramPacket(dString.getBytes(), dString.getBytes().length, address, port); System.out.println("### Sending for packet.hashCode(): " + packet.hashCode() + " | packet.getPort(): " + packet.getPort()); //Thread.sleep(5000); System.out.println("Now sending the response back to UDP client."); DatagramSocket sendingDatagramSocket = new DatagramSocket(); sendingDatagramSocket.send(packet); sendingDatagramSocket.close(); System.out.println("I am done"); } catch (IOException e) { e.printStackTrace(); } } } } 

进一步阅读

我强烈建议您阅读此 Java教程，如果不完整，那么至少“编写数据报客户端和服务器”部分。