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對於一個小型大學項目我必須編寫一個服務器和客戶端UDP通信。Java客戶端服務器UDP獲取錯誤的包
如果客戶端發送數據並且服務器只讀取，則一切正常。只要我開始從服務器發送數據到客戶端，我的小程序錯誤。
public class Sensors {
private static List<Produkt> allSensors = new ArrayList<Produkt>();
public static void main(String[] args) throws Exception {
//Preparing Our Data
initSensors();
//Server Config
String serverIP = new String();
BufferedReader eingabe = new BufferedReader(new InputStreamReader(System.in));
System.out.print("IP Eintragen:");
serverIP = eingabe.readLine();
System.out.println("");
//Preparing Data to Send
try{
DatagramSocket serverSocket = new DatagramSocket(1234);
byte[] receiveData = new byte[4];
DatagramPacket receivePacket = new DatagramPacket(receiveData,
receiveData.length);
for(;;){
//Sending
for (Produkt s : allSensors) {
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
ObjectOutputStream os = new ObjectOutputStream(outputStream);
os.writeObject(s);
byte[] sendData = outputStream.toByteArray();
InetAddress ia = InetAddress.getByName(serverIP);
DatagramPacket sendPacket= new DatagramPacket(sendData,sendData.length,ia,1223);
serverSocket.send(sendPacket);
outputStream.close();
}
for (Produkt s : allSensors) {
System.out.println(s);
}
//Empfangen
try{
serverSocket.receive(receivePacket);
String sentence = new String(receivePacket.getData(), 0,
receivePacket.getLength());
System.out.println("RECEIVED: " + sentence);
}catch(IOException e){
}
Thread.sleep(1000);
reduceValue();
}
}catch (IOException e) {
System.out.println(e);
}
}
static public void initSensors() {
allSensors.add(new Produkt("Äpfel", 0, 100, ""));
allSensors.add(new Produkt("Birnen", 0, 100, ""));
allSensors.add(new Produkt("Kiwis", 0, 100, ""));
allSensors.add(new Produkt("Bananen", 0, 100, ""));
for (Produkt s : allSensors) {
System.out.print(s.p_name + " : " + s.p_quant + "\n");
}
}
static public void reduceValue() {
for (Produkt s : allSensors) {
if (s.p_quant > 0) {
s.p_quant -= 20;
}
}
}
static public void fillValue() {
for (Produkt s : allSensors) {
s.p_quant = 100;
}
}
}
public class Fridge extends Thread {
private static int port;
private static String htmlInsert = "";
private static DataShare ds;
public Fridge(int port, DataShare ds) {
this.port = port;
this.ds = ds;
}
@Override
public void run() {
System.out.println("Start Fridge Server");
try {
handleRequest();
} catch (Exception ex) {
Logger.getLogger(Fridge.class.getName()).log(Level.SEVERE, null, ex);
}
}
static public void handleRequest() throws Exception {
try{
DatagramSocket serverSocket = new DatagramSocket(port);
byte[] recivingData = new byte[512];
DatagramPacket receivePacket = new DatagramPacket(recivingData, recivingData.length);
for(;;)
{
if(!ds.produkte.isEmpty()){
if(ds.produkte.get(0).p_quant == 0){
ds.reOrder = true;
}else{
ds.reOrder = false;
}
}
//Empfangen
serverSocket.receive(receivePacket);
//prepare Data for conversion into Produkt
recivingData = receivePacket.getData();
ByteArrayInputStream in = new ByteArrayInputStream(recivingData);
ObjectInputStream is = new ObjectInputStream(in);
Produkt reveivedProdukt = (Produkt) is.readObject();
//Decoding Produkt into DataShare
//System.out.println(reveivedProdukt);
decodeData(reveivedProdukt);
writeHTML();
//Senden
String reorder = new String();
if(ds.reOrder){
reorder = "FILL";
}else{
reorder ="NOT";
}
System.out.println(reorder);
byte[] sendingDate = reorder.getBytes("UTF-8");
DatagramPacket sendingPacket = new DatagramPacket(sendingDate, sendingDate.length,
receivePacket.getAddress(),receivePacket.getPort());
serverSocket.send(sendingPacket);
}
}catch(IOException e){
System.out.println(e);
}catch(ClassNotFoundException e){
e.printStackTrace();
}
}
static public void writeHTML() throws Exception {
List<String> lines = new ArrayList<String>(Arrays.asList("<!DOCTYPE html>\n",
"<html>\n",
" <head>\n",
" <meta charset=\"utf-8\">\n",
" <title>Test</title>\n",
" </head>\n",
" <body>\n",
"\n",
" <h1 style=\"color:red;\">Das ist ein Test</h1>\n",
"\n",
" </body>\n",
"</html>"));
htmlInsert += "<p>";
for(Produkt p : ds.produkte){
htmlInsert+= p.p_name +" Preis: " + p.p_price + " Shopname: "+
p.shop_name + " Quantity: " + p.p_quant + "</br>";
}
htmlInsert+= "</p></br>";
lines.add(6, htmlInsert);
/* WINDOWS Path file = Paths.get(".\\src\\HttpServer\\data.html");*/
/* LINUX*/ Path file = Paths.get("/home/debian/GitRepo/VSSS17/Fridge/src/HttpServer/data.html");
Files.write(file, lines, Charset.forName("UTF-8"));
}
static public void decodeData(Produkt data) {
Produkt comp = ds.getProduktByName(data.p_name);
if (!comp.p_name.equals("Fail")) {
//System.out.println("Changed" + data.p_name + "for amount: " + data.p_quant);
ds.setQuant(data.p_name, data.p_quant);
} else {
ds.addProdukt(data);
}
//System.out.println("---");
if (ds.getLegnth() != 0) {
// ds.print();
}
//System.out.println("---");
}
}
因此，一旦從Sensordata我的數量爲0，我開始發送 「填充」 字符串到我的客戶。客戶端只獲取「NOT」包。這大約持續50個包裹，直到客戶收到「FILL」包裹。在此之後，服務器發送一個「NOT」包，因爲數量回到100.但客戶仍然收到大約50個包的「FILL」包。我有不同的看法，像打開2個插座，一個用於閱讀一個寫作。但它仍然是同樣的問題。
我真的不明白爲什麼它不起作用。無法在互聯網上找到任何解決方案。也許你們可以幫助我。
UDP沒有可靠性功能。如果你想要可靠性，你必須自己編寫代碼。注意在這種情況下，單詞是'包'而不是'包'。 '數據報'會更好。 – EJP
*在調用包裝的ByteArrayOutputStream的'toByteArray（）'方法之前，需要'關閉（）'（或至少'flush（）'）ObjectOutputStream *。就我所瞭解的代碼而言。 –
什麼是實現可靠性的最佳方式？有沒有辦法在收到包之後才發送數據包？我對UDP和數據包發送很新。 –