套接字始终接收到最后一个 udp 数据包

Question

总是我可以得到第一个udp数据包，但是当我收到第二个udp数据包时，DatagramPacket总是得到最后一个数据包的一部分。

例如：我需要在第一个数据包中接收："AAAAAAAAAAA"我收到："啊

我需要在第二个数据包中接收："BBBB"我收到："BBBBAAAA"。

如何刷新，擦除或其他方法来解决我的问题？

这是我的代码：

public DatagramServer(Context c, Activity a) throws SocketException {
        setSocket(new DatagramSocket(Constantes.UDP_PORT));
        getSocket().setBroadcast(true);     
        getSocket().setReuseAddress(true);
        setContext(c);
        setActivity(a);
        Thread thread = new Thread(new Runnable() {
        @Override
            public void run() {
                try {
                    receivePacket();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
        thread.start();
    }
public void receivePacket() throws IOException {
        byte[] buf = null;
        buf = new byte[Constantes.PACKETSIZE];
        final DatagramPacket packet = new DatagramPacket(buf, buf.length);
        while (true) {
            getSocket().receive(packet);
            Handler mainHandler = new Handler(getContext().getMainLooper());
            Runnable myRunnable = new Runnable() {
                @Override
                public void run() {
                    byte[] resposta = packet.getData();
                    try {
                        Thread.sleep(200);
                    } catch (InterruptedException e1) {
                        e1.printStackTrace();
                    }
                    if (resposta[0] == 111) {
                        if (GlobalSingleton.getInstance().is_pode_reconhecer_central()){
                            final CentralDAO cDAO = new CentralDAO(getContext());
                            final Central central = new Central();
                            Central centralExistente = new Central();
                            Boolean bcentralExiste = false;
                            central.set_IP(packet.getAddress().getHostAddress());
                            central.set_mac(CentralService.getMAC(packet.getData()));
                            central.set_modificado(true);
                            central.set_ativo(true);

                            }
                            else {
                                centralExistente.set_IP(packet.getAddress().getHostAddress());
                                centralExistente.set_ativo(true);
                                for (int i=0;i<lvCentrais.getCount();i++){
                                    Central centrallv = (Central) lvCentrais.getItemAtPosition(i);
                                    if (centrallv.get_mac().equals(centralExistente.get_mac())){
                                        centrallv.set_IP(centralExistente.get_IP());
                                        centrallv.set_ativo(centralExistente.is_ativo());
                                    }
                                }
                            }
                            GlobalSingleton.getInstance().set_pode_reconhecer_central(false);
                        }
                    } else {
                        String respostaString = "";
                        try {
                            respostaString = new String(packet.getData(),"ASCII");
                        } catch (UnsupportedEncodingException e) {
                            e.printStackTrace();
                        }//new String(packet.getData(),packet.getOffset(),packet.getLength());//
                        if (respostaString.toUpperCase().contains(Constantes.ANSWER_DEVICE)) {
                            if (GlobalSingleton.getInstance().is_pode_reconhecer_dispositivo()){
                                final GeradorDAO gerDAO = new GeradorDAO(getContext());
                                final DispositivoDAO dDAO = new DispositivoDAO(getContext());
                                List<Gerador> list = gerDAO.selectAll();
                                if (list.size()>0){
                                    int mac,versao,tipo;
                                    String values[] = Utils.getValorString(respostaString, Constantes.P_COMA, Constantes.P_INDICADOR);
                                    mac = Integer.parseInt(values[0].trim());
                                    tipo = Integer.parseInt(values[1].trim());
                                    versao = Integer.parseInt(values[2].trim());
                                    if (dDAO.selectOne(mac, GlobalSingleton.getInstance().get_current_central().get_id()) == null){
                                        final Gerador gerador = gerDAO.selectOne(tipo, versao);                                 
                                        final Dispositivo dispNovo = new Dispositivo(GlobalSingleton.getInstance().get_current_central().get_id());
                                        dispNovo.set_mac(mac);
                                        dispNovo.set_tipo(tipo);
                                        dispNovo.set_versao(versao);
                                        dispNovo.set_nome(gerador.get_nome_dispositivo());

                                    }
                                    else{
                                        Toast.makeText(getContext(), "Dispositivo já existe", Toast.LENGTH_SHORT).show();
                                    }                       
                                }
                                GlobalSingleton.getInstance().set_pode_reconhecer_dispositivo(false);
                            }                           
                        }
                    }               
                }
            };
            mainHandler.post(myRunnable);
        }
    }

我是安卓的初学者，如果你能帮助我，我将不胜感激！

Answer 1

您忽略了DatagramPacket.中的长度

central.set_mac(CentralService.getMAC(packet.getData()))

应该是这样的

central.set_mac(CentralService.getMAC(packet.getData(), packet.getOffset(), packet.getLength()))

假设 getMac() 方法接受这些参数。否则，您将不得不自己创建一个适当大小的字节数组。

编辑我不打算在所有其他用途中重复packet.getData().