[Android] UDP Receive / Send 完整-可執行-附檔案-教學

花了兩三個禮拜終於把Android UDP搞定!

首先,要先搞懂Thread / Handler是甚麼,不然這篇往下看沒有意義(因為會看不懂)

在MainActivity的部分,這邊負責主要的UI介面+Handler+Thread呼叫

package com.example.thread_example;

import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Enumeration;

import android.annotation.SuppressLint;
import android.net.wifi.WifiInfo;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.os.StrictMode;
import android.support.v7.app.ActionBarActivity;
import android.text.format.Time;
import android.util.Log;
import android.widget.TextView;

@SuppressLint("NewApi")
public class MainActivity extends ActionBarActivity {

public static Handler exHandler;
private TextView txv;
private ChatServer chatserver;
private ChatSender chatsender;
public static InetAddress IP;
public WifiInfo mwifiInfo;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

if (android.os.Build.VERSION.SDK_INT > 9) {
   StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
   StrictMode.setThreadPolicy(policy);
}

txv = (TextView) findViewById(R.id.textView);
//利用handler來顯示接收到的文字
exHandler=new Handler() {
       @Override
       public void handleMessage(Message msg) {
        super.handleMessage(msg);
        String msgString = (String)msg.obj;
        Log.d("Handler","Now in Handler");
        txv.setText(null);
        txv.setText(msgString+"\n"+txv.getText().toString());
       }
   };
        //獲得Wifi的內部網路IP
   StringBuilder IFCONFIG=new StringBuilder();
   try {
       for (Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements();) {
           NetworkInterface intf = en.nextElement();
           for (Enumeration<InetAddress> enumIpAddr = intf.getInetAddresses(); enumIpAddr.hasMoreElements();) {
               InetAddress inetAddress = enumIpAddr.nextElement();
               if (!inetAddress.isLoopbackAddress() && !inetAddress.isLinkLocalAddress() && inetAddress.isSiteLocalAddress()) {
               IFCONFIG.append(inetAddress.getHostAddress().toString()+"\n");              
               }
           }
       }
       txv.setText(IFCONFIG.toString());
       Log.d("LOG_Text", IFCONFIG.toString());
   } catch (SocketException ex) {
       Log.e("LOG_TAG", ex.toString());
   }


try{
chatserver = new ChatServer();
chatserver.start();
chatsender = new ChatSender();
chatsender.start();
Log.d("User","Thread start...");

}catch(Exception e)
{
String str = e.toString();
Log.e("Error by User", str);
}

}

protected void onPause(){
super.onPause();
if(chatserver != null)
{
if(!chatserver.isInterrupted())
{
chatserver.interrupt();
}
}
}

}

有一點長,這邊元件只有拉一個TextView而已,十分簡單。

IFCONFIG 

這邊負責顯示WIFI的IP

Thread--chatserver/chatsender

則是另外開兩個java檔(與mainActivity.java同層)分別做為接收與傳送，.start()就是讓他啟動而已。

exHandler

這邊負責顯示接收到的資訊(不能用static來傳值,因為Android不支援,至於為什麼我也不清楚),並把他印出來在textview上面。

Receiver部分(chatserver.java)

package com.example.thread_example;

import java.io.IOException;

import java.net.DatagramPacket;

import java.net.DatagramSocket;

import android.os.Bundle;

import android.os.Message;

import android.util.Log;

public class ChatServer extends Thread{

private DatagramSocket server = null;

private static final int PORT = 8000;

public ChatServer() throws IOException {

server = new DatagramSocket(PORT);

Log.d("User","new server socket");

}

public void run(){

byte[] byte1024 = new byte[1024];

//Message msg = new Message();

//Bundle data = new Bundle();

DatagramPacket dPacket = new DatagramPacket(byte1024, 100);

String txt;

try{

Log.d("User","runing run()");

while(true){

server.receive(dPacket);

while(true)

{

//印出來到螢幕上

txt = new String(byte1024, 0, dPacket.getLength());

MainActivity.exHandler.sendMessage(MainActivity.exHandler.obtainMessage(1,txt));

Log.d("User","Handler send Message");

if(true) break;

}

//CloseSocket(client);//關閉

}

}

catch(IOException e)

{}

}

private void CloseSocket(DatagramSocket socket) throws IOException{

socket.close();

}

}

這邊宣告一個1024的byte來接收資料(按照你的資料量大小來調整宣告大小)

一定要宣告datagramSocket,datagramPacket,一個是連線,一個是接收封包用,至於handler這邊的

sendMessage就是回傳到MainActivity來讓textview顯示接收的資訊而已。結構上有兩個while(),第

一個while會卡在receive()這邊,一直到有封包進來才會往下跑到第二個while(),第二個則是印出資

訊,沒有甚麼特別的地方(Log是debug用的)

Sender的部分(chatsender.java)

package com.example.thread_example;

import java.io.IOException;

import java.net.DatagramPacket;

import java.net.DatagramSocket;

import java.net.InetAddress;

import java.net.SocketException;

import java.net.UnknownHostException;

import android.util.Log;

public class ChatSender extends Thread{

public void run(){

DatagramSocket socket = null;

try

{

socket = new DatagramSocket();

InetAddress serverAddress = InetAddress.getByName("192.168.10.105");

Log.d("IP Address", serverAddress.toString());

String str = "Test Thread sender";

            //創建一個用於發送的DatagramPacket對象

            DatagramPacket packet=new DatagramPacket(str.getBytes(),str.length(),serverAddress,2000); 

            //發送數據

            while(true)

            {

            socket.send(packet);

            Thread.sleep(10000);

            }

}

catch(SocketException e)

{

e.printStackTrace();

String error = e.toString();

Log.e("Error by Sender", error);

}

catch(UnknownHostException e)

{

e.printStackTrace();

String error = e.toString();

Log.e("Error by Sender", error);

}

catch(IOException e)

{

e.printStackTrace();

String error = e.toString();

Log.e("Error by Sender", error);

}

catch(Exception e)

{

e.printStackTrace();

String error = e.toString();

Log.e("Error by Sender", error);

}

finally{

if(socket != null){

socket.close();

}

}

}

}

這邊設了固定的IP(未來會再調整),只要一跑進去thread.run()就會不停的對指定IP/Port丟資訊,每

次丟完休息一秒。

記得要開啟權限在AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.thread_example"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="19" />
    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.thread_example.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

    -------------開這兩個---------------

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


完整jar檔案在此: 點這邊

*後記: Android UDP真的不是很好做,有很多很多細節 2.3.5版本跟 4.0版本已上又有差別

不過大部分比較大的問題都有寫在前面文章,有需要可以看一下。