我在JavaFx中编写UDP通信时遇到问题。
代码能够发送消息，但无法接收消息。
我应该在源代码中修改以接收消息？
以下是源代码：
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<ActionEvent>(){
@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<Number,Number> lineChart =
new LineChart<Number,Number>(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<Boolean> ss = new ScheduledService<Boolean>()
{
@Override
protected Task<Boolean> createTask()
{
Task<Boolean> task = new Task<Boolean>()
{
@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<ActionEvent> actionHandler = new EventHandler<ActionEvent>(){
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);
}
}
答案 0 :(得分：2)
您的代码非常模糊，也许我不了解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：
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。
（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);
UDP客户端希望与UDP服务器通信，因此它会打开DatagramSocket并在其上发送DatagramPacket。 DatagramPacket将包含UDP服务器的端点。
socket.send(packet);发送了消息，它就会准备使用socket.receive(packet);（{em>我认为你缺少的地方）最重要的是要理解的是，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服务器之间没有连接，因此UDP必须在发送消息后收听。sendingDatagramSocket.send(packet);发送。它将使用UDP客户端的响应和端点准备DatagramPacket。socket.receive(packet);中所述，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个端口（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服务器发送。主要问题是Send_UDP只发送但未收到，recieve_UDP只收到但不发送。
所以，基本上你需要在UDP客户端和UDP服务器上发送和接收，只是反之亦然，但你需要做两件事。
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();
}
}
}
}
我强烈建议阅读this Java教程，如果不完整，那么至少＆＃34;编写数据报客户端和服务器＆＃34;部分。