一．基礎知識
當我們開發需要和服務器交互的應用程序時，基本上都需要獲取服務器端的數據，比如《地震及時通》就需要及時獲取服務器上最新的地震信息。要獲取服務器上不定時更新的信息一般來說有兩種方法，第一種是客戶端使用Pull（拉）的方式，隔一段時間就去服務器上獲取信息，看是否有更新的信息出現。第二種就是服務器使用Push（推送）的方式，當服務器端有新信息了，則把最新的信息Push到客戶端上。
雖然Pull和Push兩種方式都能實現獲取服務器端更新信息的功能，但是明顯來說Push is better than pull。因爲Pull方式更費客戶端的網絡流量，更主要的是費電量。
Android從2.2版本開始增加了Cloud to Device Messaging（C2DM）框架，在系統中支持了Push功能，基於Android平臺使用Push功能更加簡單了。雖然C2DM目前還處在實驗室階段，不過小規模的使用應該沒問題
下面我們就來體驗一下Android的C2DM功能。
二．C2DM框架
使用Android的C2DM功能有幾個要求：
1. 需要Android2.2及以上的系統版本。
2. 使用C2DM功能的Android設備上需要設置好Google的賬戶。
3. 需要在這裏註冊使用C2DM功能的用戶郵箱賬號（最好爲C2DM單獨註冊一個Gmail郵箱賬號）。
我們接下來C2DM的一個完整過程，這裏借用一下Google官方推出的Chrome To Phone過程圖來說明下。
圖1 C2DM操作過程圖
要使用C2DM來進行Push操作，基本上要使用以下6個步驟：
（1）註冊：Android設備把使用C2DM功能的用戶賬戶（比如[email protected]）和App名稱發送給C2DM服務器。
（2）C2DM服務器會返回一個registration_id值給Android設備，設備需要保存這個registration_id值。
（3）Android設備把獲得的registration_id和C2DM功能的用戶賬戶（[email protected]）發送給自己的服務器，不過一般用戶賬戶信息因爲和服務器確定好的，所以不必發送。
這樣Android設備就完成了C2DM功能的註冊過程，接下來就可以接收C2DM服務器Push過來的消息了。
（4）服務器獲得數據。這裏圖中的例子Chrome To Phone，服務器接收到Chrome瀏覽器發送的數據。數據也可以是服務器本地產生的。這裏的服務器是Google AppEngine（很好的一項服務，可惜在國內被屏了），要換成自己的服務器。服務器還要獲取註冊使用C2DM功能的用戶賬戶（[email protected]）的ClientLogin權限Auth。
（5）服務器把要發送的數據和registration_id一起，並且頭部帶上獲取的Auth，使用POST的方式發送給C2DM服務器。
（6）C2DM服務器會以Push的方式把數據發送給對應的Android設備，Android設備只要在程序中按之前和服務器商量好的格式從對應的key中獲取數據即可。
這樣我們就大概明白了C2DM的工作流程，下面我們就結合一個實例來具體的說明以上6個步驟。
三．實例開發
我們要創建的程序名稱爲AndroidC2DMDemo，包名爲com.ichliebephone.c2dm。
開始之前我們先去C2DM網頁上註冊一下使用C2DM功能的用戶賬戶。
圖2 應用程序名
其中應用程序名要填寫帶包名的完整名稱，比如這裏爲om.ichliebephone.c2dm. AndroidC2DMDemo。
圖3 C2DM用戶賬戶註冊
這裏的contact郵箱使用一個你能接收到郵件的郵箱即可，下面的Role（sender）account郵箱最好單獨註冊一個Gmail郵箱來使用C2DM服務。我們這裏使用的是專門註冊的[email protected]郵箱。
提交後，過一段時間就會收到Google發送過來的確認郵件，然後你就可以使用C2DM的Push服務了。
介紹了這麼多，我們先來快速完成一個實例，只完成Android設備端的註冊部分，不包含向服務器發送registration_id和服務器向C2DM服務器發送數據的具體代碼，這部分只是用Ubuntu下的curl命令來模擬，主要是快速親自體驗一下Push的結果。
創建一個Android工程AndroidC2DMDemo，並且包含進Google的開源例子Chrome To Phone中的c2dm包com.google.android.c2dm，包中包含三個Java類，分別爲：
第一個類爲C2DMBaseReceiver：
/*
* Copyright 2010 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.android.c2dm;
import java.io.IOException;
import android.app.AlarmManager;
import android.app.IntentService;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.PowerManager;
import android.util.Log;
/**
* Base class for C2D message receiver. Includes constants for the
* strings used in the protocol.
*/
/**
* 接收和處理C2DM消息的基類
* */
public abstract class C2DMBaseReceiver extends IntentService {
//和C2DM Push的Intent內容相關
//重新向C2DM服務器註冊
private static final String C2DM_RETRY = "com.google.android.c2dm.intent.RETRY";
//向C2DM服務器註冊後的回調處理
public static final String REGISTRATION_CALLBACK_INTENT = "com.google.android.c2dm.intent.REGISTRATION";
//接收到C2DM服務器的推送消息
private static final String C2DM_INTENT = "com.google.android.c2dm.intent.RECEIVE";
// Logging tag
private static final String TAG = "C2DM";
// Extras in the registration callback intents.
//向C2DM註冊返回的intent中包含的key
public static final String EXTRA_UNREGISTERED = "unregistered";
public static final String EXTRA_ERROR = "error";
public static final String EXTRA_REGISTRATION_ID = "registration_id";
//向C2DM註冊出錯的原因
public static final String ERR_SERVICE_NOT_AVAILABLE = "SERVICE_NOT_AVAILABLE";
public static final String ERR_ACCOUNT_MISSING = "ACCOUNT_MISSING";
public static final String ERR_AUTHENTICATION_FAILED = "AUTHENTICATION_FAILED";
public static final String ERR_TOO_MANY_REGISTRATIONS = "TOO_MANY_REGISTRATIONS";
public static final String ERR_INVALID_PARAMETERS = "INVALID_PARAMETERS";
public static final String ERR_INVALID_SENDER = "INVALID_SENDER";
public static final String ERR_PHONE_REGISTRATION_ERROR = "PHONE_REGISTRATION_ERROR";
// wakelock
private static final String WAKELOCK_KEY = "C2DM_LIB";
private static PowerManager.WakeLock mWakeLock;
private final String senderId;
/**
* The C2DMReceiver class must create a no-arg constructor and pass the
* sender id to be used for registration.
*/
public C2DMBaseReceiver(String senderId) {
// senderId is used as base name for threads, etc.
super(senderId);
this.senderId = senderId;
}
//下面幾個是接收到C2DM Push過來的信息後的回調函數，都可以在繼承的子類中處理
/**
* Called when a cloud message has been received.
*/
/**
* 接收到C2DM服務器Push的消息後的回調函數，需要在繼承的子類中處理
* */
protected abstract void onMessage(Context context, Intent intent);
/**
* Called on registration error. Override to provide better
* error messages.
*
* This is called in the context of a Service - no dialog or UI.
*/
/**
* 出錯的回調函數
* */
public abstract void onError(Context context, String errorId);
/**
* Called when a registration token has been received.
*/
/**
* 註冊後的回調函數
* */
public void onRegistered(Context context, String registrationId) throws IOException {
// registrationId will also be saved
}
/**
* Called when the device has been unregistered.
*/
/**
* 取消註冊的回調函數
* */
public void onUnregistered(Context context) {
}
//IntentService的方法
@Override
public final void onHandleIntent(Intent intent) {
try {
Context context = getApplicationContext();
if (intent.getAction().equals(REGISTRATION_CALLBACK_INTENT)) {
handleRegistration(context, intent);//處理註冊後的回調
} else if (intent.getAction().equals(C2DM_INTENT)) {
onMessage(context, intent);//處理C2DM Push消息的回調
} else if (intent.getAction().equals(C2DM_RETRY)) {
C2DMessaging.register(context, senderId); //重新註冊
}
} finally {
// Release the power lock, so phone can get back to sleep.
// The lock is reference counted by default, so multiple
// messages are ok.
// If the onMessage() needs to spawn a thread or do something else,
// it should use it's own lock.
mWakeLock.release();
}
}
/**
* Called from the broadcast receiver.
* Will process the received intent, call handleMessage(), registered(), etc.
* in background threads, with a wake lock, while keeping the service
* alive.
*/
static void runIntentInService(Context context, Intent intent) {
if (mWakeLock == null) {
// This is called from BroadcastReceiver, there is no init.
PowerManager pm =
(PowerManager) context.getSystemService(Context.POWER_SERVICE);
mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,
WAKELOCK_KEY);
}
mWakeLock.acquire();
// Use a naming convention, similar with how permissions and intents are
// used. Alternatives are introspection or an ugly use of statics.
String receiver = context.getPackageName() + ".C2DMReceiver";
intent.setClassName(context, receiver);
context.startService(intent);
}
//處理註冊後的回調
private void handleRegistration(final Context context, Intent intent) {
final String registrationId = intent.getStringExtra(EXTRA_REGISTRATION_ID);
String error = intent.getStringExtra(EXTRA_ERROR);
String removed = intent.getStringExtra(EXTRA_UNREGISTERED);
Log.v(TAG, "handleRegistration");
//打印出接收到的registraton_id
Log.v(TAG, "dmControl: registrationId = " + registrationId +
", error = " + error + ", removed = " + removed);
if (Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG, "dmControl: registrationId = " + registrationId +
", error = " + error + ", removed = " + removed);
}
if (removed != null) {
// Remember we are unregistered
C2DMessaging.clearRegistrationId(context);
onUnregistered(context);
return;
} else if (error != null) {
// we are not registered, can try again
C2DMessaging.clearRegistrationId(context);
// Registration failed
Log.e(TAG, "Registration error " + error);
onError(context, error);
if ("SERVICE_NOT_AVAILABLE".equals(error)) {
long backoffTimeMs = C2DMessaging.getBackoff(context);
Log.d(TAG, "Scheduling registration retry, backoff = " + backoffTimeMs);
Intent retryIntent = new Intent(C2DM_RETRY);
PendingIntent retryPIntent = PendingIntent.getBroadcast(context,
0 /*requestCode*/, retryIntent, 0 /*flags*/);
AlarmManager am = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
am.set(AlarmManager.ELAPSED_REALTIME,
backoffTimeMs, retryPIntent);
// Next retry should wait longer.
backoffTimeMs *= 2;
C2DMessaging.setBackoff(context, backoffTimeMs);
}
} else {
try {
onRegistered(context, registrationId);
C2DMessaging.setRegistrationId(context, registrationId);
} catch (IOException ex) {
Log.e(TAG, "Registration error " + ex.getMessage());
}
}
}
}
第二個類爲C2DMBroadcastReceiver：
/*
*/
package com.google.android.c2dm;
import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
/**
* Helper class to handle BroadcastReciver behavior.
* - can only run for a limited amount of time - it must start a real service
* for longer activity
* - must get the power lock, must make sure it's released when all done.
*
*/
/**
* 幫助類，幫忙處理BroadcastReciver過程
* */
public class C2DMBroadcastReceiver extends BroadcastReceiver {
@Override
public final void onReceive(Context context, Intent intent) {
// To keep things in one place.
C2DMBaseReceiver.runIntentInService(context, intent);
setResult(Activity.RESULT_OK, null /* data */, null /* extra */);
}
}
第三個類爲C2DMessaging：
/*
* Copyright 2010 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.android.c2dm;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
/**
* Utilities for device registration.
*
* Will keep track of the registration token in a private preference.
*/
/**
* 和註冊相關的一些實用函數
* */
public class C2DMessaging {
public static final String EXTRA_SENDER = "sender";
public static final String EXTRA_APPLICATION_PENDING_INTENT = "app";
public static final String REQUEST_UNREGISTRATION_INTENT = "com.google.android.c2dm.intent.UNREGISTER";
public static final String REQUEST_REGISTRATION_INTENT = "com.google.android.c2dm.intent.REGISTER";
public static final String LAST_REGISTRATION_CHANGE = "last_registration_change";
public static final String BACKOFF = "backoff";
public static final String GSF_PACKAGE = "com.google.android.gsf"; //GSF爲GoogleServicesFramework.apk的縮寫
// package
static final String PREFERENCE = "com.google.android.c2dm";
private static final long DEFAULT_BACKOFF = 30000;
/**
* Initiate c2d messaging registration for the current application
*/
public static void register(Context context,
String senderId) {
Intent registrationIntent = new Intent(REQUEST_REGISTRATION_INTENT);
registrationIntent.setPackage(GSF_PACKAGE);
registrationIntent.putExtra(EXTRA_APPLICATION_PENDING_INTENT,
PendingIntent.getBroadcast(context, 0, new Intent(), 0));
registrationIntent.putExtra(EXTRA_SENDER, senderId);
context.startService(registrationIntent);
// TODO: if intent not found, notification on need to have GSF
}
/**
* Unregister the application. New messages will be blocked by server.
*/
public static void unregister(Context context) {
Intent regIntent = new Intent(REQUEST_UNREGISTRATION_INTENT);
regIntent.setPackage(GSF_PACKAGE);
regIntent.putExtra(EXTRA_APPLICATION_PENDING_INTENT, PendingIntent.getBroadcast(context,
0, new Intent(), 0));
context.startService(regIntent);
}
/**
* Return the current registration id.
*
* If result is empty, the registration has failed.
*
* @return registration id, or empty string if the registration is not complete.
*/
public static String getRegistrationId(Context context) {
final SharedPreferences prefs = context.getSharedPreferences(
PREFERENCE,
Context.MODE_PRIVATE);
String registrationId = prefs.getString("dm_registration", "");
return registrationId;
}
public static long getLastRegistrationChange(Context context) {
final SharedPreferences prefs = context.getSharedPreferences(
PREFERENCE,
Context.MODE_PRIVATE);
return prefs.getLong(LAST_REGISTRATION_CHANGE, 0);
}
static long getBackoff(Context context) {
final SharedPreferences prefs = context.getSharedPreferences(
PREFERENCE,
Context.MODE_PRIVATE);
return prefs.getLong(BACKOFF, DEFAULT_BACKOFF);
}
static void setBackoff(Context context, long backoff) {
final SharedPreferences prefs = context.getSharedPreferences(
PREFERENCE,
Context.MODE_PRIVATE);
Editor editor = prefs.edit();
editor.putLong(BACKOFF, backoff);
editor.commit();
}
// package
static void clearRegistrationId(Context context) {
final SharedPreferences prefs = context.getSharedPreferences(
PREFERENCE,
Context.MODE_PRIVATE);
Editor editor = prefs.edit();
editor.putString("dm_registration", "");
editor.putLong(LAST_REGISTRATION_CHANGE, System.currentTimeMillis());
editor.commit();
}
// package
static void setRegistrationId(Context context, String registrationId) {
final SharedPreferences prefs = context.getSharedPreferences(
PREFERENCE,
Context.MODE_PRIVATE);
Editor editor = prefs.edit();
editor.putString("dm_registration", registrationId);
editor.commit();
}
}
代碼中已添加了部分中文註釋，可以先大概瞭解下，等整個工程建立完了在一起解釋。
然後創建我們自己的包com.ichliebephone.c2dm，包含兩個類，一個是工程的入口AndroidC2DMDemo：
package com.ichliebephone.c2dm;
import com.google.android.c2dm.C2DMessaging;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
public class AndroidC2DMDemo extends Activity {
/** Called when the activity is first created. */
private static final String TAG = "AndroidC2DMDemo";
public static final String SENDER_ID = "[email protected]"; //使用C2DM服務的用戶賬戶
public static final String MESSAGE_KEY_ONE = "msg"; //和服務器商量好的接收消息的鍵值key
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Log.v(TAG, "Start");
//向C2DM服務器註冊
C2DMessaging.register(this, SENDER_ID);
}
}
很簡單，就是開始向C2DM服務器進行註冊。
另一個類爲C2DMBaseReceiver的子類C2DMReceiver：
package com.ichliebephone.c2dm;
import java.io.IOException;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import com.google.android.c2dm.C2DMBaseReceiver;
//接收C2DM服務器Push的消息，包括註冊返回的registration_id消息，推送的數據消息等
public class C2DMReceiver extends C2DMBaseReceiver{
private static final String TAG="C2DMReceiver";
//
public C2DMReceiver()
{
super(AndroidC2DMDemo.SENDER_ID);
}
public C2DMReceiver(String senderId) {
super(senderId);
// TODO Auto-generated constructor stub
}
//接收到Push消息的回調函數
@Override
protected void onMessage(Context context, Intent intent) {
// TODO Auto-generated method stub
Log.v(TAG, "C2DMReceiver message");
Bundle extras = intent.getExtras();
if(extras!=null){
String msg = (String)extras.get(AndroidC2DMDemo.MESSAGE_KEY_ONE);
Log.v(TAG, "The received msg = "+msg);
//在標題欄上顯示通知
NotificationManager notificationManager = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);
Notification notification = new Notification(R.drawable.icon, msg, System.currentTimeMillis());
PendingIntent contentIntent = PendingIntent.getActivity(this, 0, new Intent(this, AndroidC2DMDemo.class), 0);
notification.setLatestEventInfo(this, getString(R.string.app_name), msg, contentIntent);
notificationManager.notify(0, notification);
}
}
@Override
public void onError(Context context, String errorId) {
// TODO Auto-generated method stub
Log.v(TAG, "C2DMReceiver error");
}
@Override
public void onRegistered(Context context, String registrationId)
throws IOException {
// TODO Auto-generated method stub
super.onRegistered(context, registrationId);
Log.v(TAG, "C2DMReceiver Register");
}
@Override
public void onUnregistered(Context context) {
// TODO Auto-generated method stub
super.onUnregistered(context);
Log.v(TAG, "C2DMReceiver UnRegister");
}
}
在這個類中我們主要在接收到Push的回調函數onMessage中對消息進行了接收，並且使用Notification的方式顯示在狀態欄上。
我們完整的工程目錄是這樣的：
圖4 工程目錄
最後我們還要在AndroidManifest.xml中增加對應的權限等內容:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.ichliebephone.c2dm"
android:versionCode="1"
android:versionName="1.0">
<uses-sdk android:minSdkVersion="8" />
<!--Only this application can receive the message and registration result -->
<!-- 設置一個權限，使只有這個應用才能接收到對應Push的消息及註冊時返回的結果 -->
<permission android:name="com.ichliebephone.c2dm.permission.C2D_MESSAGE"
android:protectionLevel="signature"></permission>
<uses-permission android:name="com.ichliebephone.c2dm.permission.C2D_MESSAGE"/>
<!-- This application has the permission to register and receive c2dm message -->
<!-- 設置註冊和接收C2DM Push消息的權限 -->
<uses-permission android:name="com.google.android.c2dm.permission.RECEIVE" />
<!-- Send and registration id to the server -->
<!-- 設置聯網權限，在把registration_id發送給服務器的時候要用 -->
<uses-permission android:name="android.permission.INTERNET" />
<!-- App must have this permission to use the library -->
<!-- 其他和獲取手機中用戶賬戶相關的權限 -->
<uses-permission android:name="android.permission.WAKE_LOCK" />
<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<uses-permission android:name="android.permission.USE_CREDENTIALS" />
<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".AndroidC2DMDemo"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<!-- In order to use the c2dm library, an
application must declare a class with the name C2DMReceiver, in its
own package, extending com.google.android.c2dm.C2DMBaseReceiver
It must also include this section in the manifest. -->
<!-- 爲了使用c2dm包com.google.android.c2dm及其對應的3個類，我們需要聲明一個
繼承com.google.android.c2dm.C2DMBaseReceiver類的子類C2DMReceiver，
並且要在這聲明下 -->
<service android:name=".C2DMReceiver" />
<!-- Only google service can send data messages for the app. If permission is not set -
any other app can generate it -->
<!-- 谷歌的C2DM服務只爲這個程序發送數據，聲明對應的權限 -->
<receiver android:name="com.google.android.c2dm.C2DMBroadcastReceiver"
android:permission="com.google.android.c2dm.permission.SEND">
<!-- Receive the actual message -->
<!-- 可以接收實際的Push數據 -->
<intent-filter>
<action android:name="com.google.android.c2dm.intent.RECEIVE" />
<category android:name="com.ichliebephone.c2dm" />
</intent-filter>
<!-- Receive the registration id -->
<!-- 可以接收註冊後返回的registration_id -->
<intent-filter>
<action android:name="com.google.android.c2dm.intent.REGISTRATION" />
<category android:name="com.ichliebephone.c2dm" />
</intent-filter>
</receiver>
</application>
</manifest>
因爲C2DM功能只有2.2及以上的Android系統才支持，因此創建一個2.2及以上的AVD，然後在”設置->賬戶與同步”裏還要設置好Google Account，如下圖所示：
圖5 設置Android設備中的Google賬戶
然後就可以運行程序了，我們會在DDMS輸出中看到獲得的registration_id：
圖6 獲得的registration_id
如果第一次運行沒有出現，試着再運行一次。
有了registration_id，我們的服務器端就可以向C2DM端發送需要Push的數據了，這裏進行簡單化處理下，在Ubuntu下直接使用curl命令來模擬服務器功能向C2DM發送數據。
我們先來獲取C2DM的ClientLogin權限Auth，在Ubuntu終端下輸入：
lingaohe@lingaohe-laptop:~$ curl -d "accountType=HOSTED_OR_GOOGLE&[email protected]&Passwd=androidc2dmdemo&service=ac2dm&source=bupt-c2dmdemo-1.0" https://www.google.com/accounts/ClientLogin
這個表示以POST的方式向https://www.google.com/accounts/ClientLogin發送數據，其中把Email和Passwd換成你自己在C2DM網頁上註冊的郵箱號和密碼。
如果你的郵箱已在C2DM網頁上註冊，並且密碼沒有錯誤的話就會返回需要的Auth內容：
SID=DQAAAKYAAADcTtHbBBNcZJEOfkfVRycD_ZOIidwsQ3UwIY7cSrYWaY6uhlfo0l9gRPB-mQxP4K2T5tWiG--vWVmSTeq5p8SPwgnsYvfzj7bkNiPPIy4xRimVVfBmAHnZgLohw7gHMKi5DS6kK-Ut5tNzdTkI0I2tUDF0ryQ7MnPpI6Sj-gUCyBXmvKatHHDnNTTV78XdGIx7FYej1DyqGsPsYo3bCstHgltjv3cd2Hs7D4yrpUWHZw
LSID=DQAAAKgAAABCpaoUE4XvxM24Cofntw1IUGx5fKxX-m7aqTL0zhunP0OjzJ2sn9ywmPa1BMZ2cF2IchuxHFLVzaSQfydAmiHZJGXLgaUorpIN6yz1e0VFWKmS6j4wGjZOos3QoJ9rkha0jKbOiHfBesADjxk-qjJ24TJ0RL-xkZHQyzS69YlA1KyzqIKjAMCzgqaDfCwhqxylJzizJksO2h8xpAFXZ38d_grm8XYZtzejiCiAMAR65A
Auth=DQAAAKoAAACRF4pgYULnXULoWgbwfdqmMiRhfZYa1l-LW_rwGD7cofov4L4c2bVrtCOXbEbkju_hhqdAonpMkrb5icptt28fU8c-s-u1y2MXNYDxPIdQzfA2t6oI3NTmyj35MpsR1NKL4TN7ZVEn6z9NueuiKAqLHukZYh1YMGkGC8M6rVvA7AWPW36064XCQED7KLVNp_pGT00lrni7UdZKZWEy0FT-EVR-OxDyHWw6C-5Kmfkisw
返回的內容包括SID，LSID和Auth三個部分，其中Auth是我們需要的內容。
有了Auth和registration_id值後，我們就可以繼續用curl命令模擬我們自己服務器的功能向C2DM發送要推送的數據：
lingaohe@lingaohe-laptop:~$ curl -H "Authorization:GoogleLogin auth=DQAAAKoAAACRF4pgYULnXULoWgbwfdqmMiRhfZYa1l-LW_rwGD7cofov4L4c2bVrtCOXbEbkju_hhqdAonpMkrb5icptt28fU8c-s-u1y2MXNYDxPIdQzfA2t6oI3NTmyj35MpsR1NKL4TN7ZVEn6z9NueuiKAqLHukZYh1YMGkGC8M6rVvA7AWPW36064XCQED7KLVNp_pGT00lrni7UdZKZWEy0FT-EVR-OxDyHWw6C-5Kmfkisw" -d "registration_id=APA91bGUBoSvt3G5Ny9t0IGLmIKAKYX6G6VHwSQHh3tP2fqcaQ0N4GPdKh5B3RDUHFCFF06YwT8ifOP_cOy5BAWyCLHL8d8NpuIW9AqXt9h2JSBVF2MitZA&collapse_key=1&data.msg=ichliebejiajia" https://android.apis.google.com/c2dm/send
其中發送的數據部分爲data.msg=ichliebejiajia，表示發送的數據內容爲ichliebejiajia，鍵值爲msg，鍵值得和Android終端上的程序統一好，以便終端上可以獲取。如果發送成功，會返回一個id值，比如：
id=0:1308623423080544%6c5c15c200000031
lingaohe@lingaohe-laptop:~$
這時我們的服務器就已經把數據發送給C2DM服務器了，Android設備上一會就能接收到C2DM服務器Push的數據。
在我們的例子中我們可以看到DDMS中打印出的消息：
圖7 獲取到的Push數據
同時Android模擬器的狀態欄上會有對應的通知顯示：
圖8 Android模擬器接收到的Push數據
這樣我們就快速實現了下Android的C2DM框架的Push功能。進一步的具體解釋說明及服務器端的代碼處理我們以後再學習。
文章對應的完整代碼例子下載地址：