Question

我能够通过UDP套接字正确发送数据，但是当我收到数据时，它一直在等待接收命令，我不知道是什么导致了这一点。请看下面的代码。

我能够从Android设备正确接收服务器端的数据，但是当我从服务器端向Android设备发送数据时，它无法接收。但是当我将数据从服务器发送到任何其他客户端，例如PC应用程序时，它会接收并正确显示数据。

class Task implements Runnable {
    @Override
    public void run() {
        try {
            String messageStr = "feed";
            int server_port = 8888;
            InetAddress local = InetAddress.getByName("10.0.2.2");
            int msg_length = messageStr.length();
            byte[] message = messageStr.getBytes();


            DatagramSocket s = new DatagramSocket();
           // 

            DatagramPacket p = new DatagramPacket(message, msg_length, local, server_port);
            s.send(p);//properly able to send data. i receive data to server

            for (int i = 0; i <= 20; i++) {
                final int value = i;
                message = new byte[30000];
                p = new DatagramPacket(message,message.length );
                s.receive(p); //keeps on waiting here but i am sending data back from server, but it never receives
                final byte[] data =  p.getData();;
                try {



                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                handler.post(new Runnable() {
                    @Override
                    public void run() {
                        progressBar.setProgress(value);
                        imageView.setImageBitmap(BitmapFactory.decodeByteArray(data,0,data.length));
                    }
                });
            }
        }
        catch(Exception ex)
        {

        }
    }
}

Answer 1

Eclipse中的文档：

从此套接字接收数据包并将其存储在参数包中。必须根据收到的数据设置pack的所有字段。如果接收的数据长于被截断的数据包缓冲区大小。此方法将阻塞，直到收到数据包或超时过期。

“s.receive(p);”命令阻止线程，直到它接收到数据或者使用setSoTimeout（timeout）设置的超时结束。

我已经完成了2个班级来进行沟通。第一个UDP服务器：

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import android.annotation.SuppressLint;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Build;

public class UDP_Server 
{
    private AsyncTask<Void, Void, Void> async;
    private boolean Server_aktiv = true;

    @SuppressLint("NewApi")
    public void runUdpServer() 
    {
        async = new AsyncTask<Void, Void, Void>() 
        {
            @Override
            protected Void doInBackground(Void... params)
            {   
                byte[] lMsg = new byte[4096];
                DatagramPacket dp = new DatagramPacket(lMsg, lMsg.length);
                DatagramSocket ds = null;

                try 
                {
                    ds = new DatagramSocket(Main.SERVER_PORT);

                    while(Server_aktiv)
                    {
                        ds.receive(dp);

                        Intent i = new Intent();
                        i.setAction(Main.MESSAGE_RECEIVED);
                        i.putExtra(Main.MESSAGE_STRING, new String(lMsg, 0, dp.getLength()));
                        Main.MainContext.getApplicationContext().sendBroadcast(i);
                    }
                } 
                catch (Exception e) 
                {
                    e.printStackTrace();
                } 
                finally 
                {
                    if (ds != null) 
                    {
                        ds.close();
                    }
                }

                return null;
            }
        };

        if (Build.VERSION.SDK_INT >= 11) async.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
        else async.execute();
    }

    public void stop_UDP_Server()
    {
        Server_aktiv = false;
    }
}

我将收到的数据发送到BroadcastReceiver，你可以在那里做任何你想要的数据。

现在我的客户端发送数据。在这段代码中我发送了一个广播，但我认为更改发送到直接IP或其他东西的代码是没有问题的。

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import android.annotation.SuppressLint;
import android.os.AsyncTask;
import android.os.Build;

public class UDP_Client 
{
    private AsyncTask<Void, Void, Void> async_cient;
    public String Message;

    @SuppressLint("NewApi")
    public void NachrichtSenden()
    {
        async_cient = new AsyncTask<Void, Void, Void>() 
        {
            @Override
            protected Void doInBackground(Void... params)
            {   
                DatagramSocket ds = null;

                try 
                {
                    ds = new DatagramSocket();
                    DatagramPacket dp;                          
                    dp = new DatagramPacket(Message.getBytes(), Message.length(), Main.BroadcastAddress, Main.SERVER_PORT);
                    ds.setBroadcast(true);
                    ds.send(dp);
                } 
                catch (Exception e) 
                {
                    e.printStackTrace();
                }
                finally 
                {
                    if (ds != null) 
                    {   
                        ds.close();
                    }
                }
                return null;
            }

            protected void onPostExecute(Void result) 
            {
               super.onPostExecute(result);
            }
        };

        if (Build.VERSION.SDK_INT >= 11) async_cient.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
        else async_cient.execute();
    }

以下是如何从主类中实例化类。

            //start UDP server
        Server = new UDP_Server();
        Server.runUdpServer();

        //UDP Client erstellen
        Client = new UDP_Client();

这里是如何向客户发送消息。

                                    //Set message
                Client.Message = "Your message";
                                    //Send message
                Client.NachrichtSenden();

要停止UDP_Server，只需将Server.Server_aktiv设置为false。

要设置上面的消息，您还可以编写“setMessage（String message）”方法或类似的东西。

Answer 2

在这篇文章中，您将找到在设备之间或同一手机中的两个应用程序之间建立套接字的详细代码。

您必须创建两个应用程序来测试下面的代码。

在两个应用程序的清单文件中，添加以下权限

<uses-permission android:name="android.permission.INTERNET" />

第一个应用代码：UDP客户端套接字

<强> activity_main.xml中

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TableRow
        android:id="@+id/tr_send_message"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:layout_marginTop="11dp">

        <EditText
            android:id="@+id/edt_send_message"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:layout_marginRight="10dp"
            android:layout_marginLeft="10dp"
            android:hint="Enter message"
            android:inputType="text" />

        <Button
            android:id="@+id/btn_send"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginRight="10dp"
            android:text="Send" />
    </TableRow>

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_below="@+id/tr_send_message"
        android:layout_marginTop="25dp"
        android:id="@+id/scrollView2">

        <TextView
            android:id="@+id/tv_reply_from_server"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical" />
    </ScrollView>

</RelativeLayout>

<强> UDPClientSocketActivity.java

import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

/**
 * Created by Girish Bhalerao on 5/4/2017.
 */

public class UDPClientSocketActivity extends AppCompatActivity implements View.OnClickListener {

    private TextView mTextViewReplyFromServer;
    private EditText mEditTextSendMessage;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button buttonSend = (Button) findViewById(R.id.btn_send);

        mEditTextSendMessage = (EditText) findViewById(R.id.edt_send_message);
        mTextViewReplyFromServer = (TextView) findViewById(R.id.tv_reply_from_server);

        buttonSend.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {

        switch (v.getId()) {

            case R.id.btn_send:
                sendMessage(mEditTextSendMessage.getText().toString());
                break;
        }
    }

    private void sendMessage(final String message) {

        final Handler handler = new Handler();
        Thread thread = new Thread(new Runnable() {

            String stringData;

            @Override
            public void run() {

                    DatagramSocket ds = null;
                    try {
                        ds = new DatagramSocket();
                        // IP Address below is the IP address of that Device where server socket is opened.
                        InetAddress serverAddr = InetAddress.getByName("xxx.xxx.xxx.xxx");
                        DatagramPacket dp;
                        dp = new DatagramPacket(message.getBytes(), message.length(), serverAddr, 9001);
                        ds.send(dp);

                        byte[] lMsg = new byte[1000];
                        dp = new DatagramPacket(lMsg, lMsg.length);
                        ds.receive(dp);
                        stringData = new String(lMsg, 0, dp.getLength());

                    } catch (IOException e) {
                        e.printStackTrace();
                    } finally {
                        if (ds != null) {
                            ds.close();
                        }
                    }

                handler.post(new Runnable() {
                    @Override
                    public void run() {

                        String s = mTextViewReplyFromServer.getText().toString();
                        if (stringData.trim().length() != 0)
                            mTextViewReplyFromServer.setText(s + "\nFrom Server : " + stringData);

                    }
                });
            }
        });

        thread.start();
    }
}

第二个应用程序代码 - UDP服务器套接字

<强> activity_main.xml中

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/btn_stop_receiving"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="STOP Receiving data"
        android:layout_alignParentTop="true"
        android:enabled="false"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="89dp" />

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@+id/btn_stop_receiving"
        android:layout_marginTop="35dp"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true">

        <TextView
            android:id="@+id/tv_data_from_client"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical" />
    </ScrollView>

    <Button
        android:id="@+id/btn_start_receiving"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="START Receiving data"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="14dp" />
</RelativeLayout>

<强> UDPServerSocketActivity.java

import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;

/**
 * Created by Girish Bhalerao on 5/4/2017.
 */

public class UDPServerSocketActivity extends AppCompatActivity implements View.OnClickListener {

    final Handler handler = new Handler();

    private Button buttonStartReceiving;
    private Button buttonStopReceiving;
    private TextView textViewDataFromClient;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        buttonStartReceiving = (Button) findViewById(R.id.btn_start_receiving);
        buttonStopReceiving = (Button) findViewById(R.id.btn_stop_receiving);
        textViewDataFromClient = (TextView) findViewById(R.id.tv_data_from_client);

        buttonStartReceiving.setOnClickListener(this);
        buttonStopReceiving.setOnClickListener(this);

    }

    private void startServerSocket() {

        Thread thread = new Thread(new Runnable() {

            private String stringData = null;

            @Override
            public void run() {

                byte[] msg = new byte[1000];
                DatagramPacket dp = new DatagramPacket(msg, msg.length);
                DatagramSocket ds = null;
                try {
                    ds = new DatagramSocket(9001);
                    //ds.setSoTimeout(50000);
                    ds.receive(dp);

                    stringData = new String(msg, 0, dp.getLength());
                    updateUI(stringData);

                    String msgToSender = "Bye Bye ";
                    dp = new DatagramPacket(msgToSender.getBytes(), msgToSender.length(), dp.getAddress(), dp.getPort());
                    ds.send(dp);

                } catch (IOException e) {
                    e.printStackTrace();
                } finally {
                    if (ds != null) {
                        ds.close();
                    }
                }
            }

        });
        thread.start();
    }

    private void updateUI(final String stringData) {

        handler.post(new Runnable() {
            @Override
            public void run() {

                String s = textViewDataFromClient.getText().toString();
                if (stringData.trim().length() != 0)
                    textViewDataFromClient.setText(s + "\n" + "From Client : " + stringData);
            }
        });
    }

    @Override
    public void onClick(View v) {

        switch (v.getId()) {

            case R.id.btn_start_receiving:

                startServerSocket();

                buttonStartReceiving.setEnabled(false);
                buttonStopReceiving.setEnabled(true);
                break;

            case R.id.btn_stop_receiving:

                //Add logic to stop server socket yourself

                buttonStartReceiving.setEnabled(true);
                buttonStopReceiving.setEnabled(false);
                break;
        }
    }
}

在UDP Socket java android上发送和接收数据

2 个答案: