一、MQTT简介
MQTT是IBM开发的一个即时通讯协议，有可能成为物联网的重要组成部分。该协议支持所有平台，几乎可以把所有联网物品和外部连接起来，被用来当做传感器和致动器（比如通过Twitter让房屋联网）的通信协议。
Apache Apollo是一个代理服务器，其是在ActiveMQ基础上发展而来的，可以支持STOMP, AMQP, MQTT, Openwire, SSL, and WebSockets 等多种协议。
总结来说MQTT只是一种消息推送的协议目前(2016/1/13)为V3.1版本，而Apache Apollo是更具这种协议而开发的一款服务性的服务程序，被用来进行消息推送。同样的服务还有Mosquitto,
二，特征
MQTT协议工作在低带宽、不可靠的网络的远程传感器和控制设备通讯而设计的协议，它具有以下主要的几项特性：
（1）使用发布/订阅消息模式，提供一对多的消息发布，解除应用程序耦合。
（2）对负载内容屏蔽的消息传输。
（3）使用TCP/IP提供网络连接。
主流的MQTT是基于TCP连接进行数据推送的，但是同样有基于UDP的版本，叫做MQTT-SN。这两种版本由于基于不同的连接方式，优缺点自然也就各有不同了。
（4）有三种消息发布服务质量：
“至多一次”，消息发布完全依赖底层TCP/IP网络。会发生消息丢失或重复。这一级别可用于如下情况，环境传感器数据，丢失一次读记录无所谓，因为不久后还会有第二次发送。这一种方式主要普通APP的推送，倘若你的智能设备在消息推送时未联网，推送过去没收到，再次联网也就收不到了。
“至少一次”，确保消息到达，但消息重复可能会发生。
“只有一次”，确保消息到达一次。在一些要求比较严格的计费系统中，可以使用此级别。在计费系统中，消息重复或丢失会导致不正确的结果。这种最高质量的消息发布服务还可以用于即时通讯类的APP的推送，确保用户收到且只会收到一次。
（5）小型传输，开销很小（固定长度的头部是2字节），协议交换最小化，以降低网络流量。
这就是为什么在介绍里说它非常适合“在物联网领域，传感器与服务器的通信，信息的收集”，要知道嵌入式设备的运算能力和带宽都相对薄弱，使用这种协议来传递消息再适合不过了。
三、原理
Apache Apollo说白了其实很简单，就是在服务器端创建一个唯一订阅号，发送者可以向这个订阅号中发东西，然后接受者（即订阅了这个订阅号的人）都会收到这个订阅号发出来的消息。以此来完成消息的推送。服务器其实是一个消息中转站。
四、centos7系统安装apache apollo
- 安装jdk
- 下载解压
- wget http://mirrors.hust.edu.cn/apache/activemq/activemq-apollo/1.7.1/apache-apollo-1.7.1-unix-distro.tar.gz
- tar -zxvf apache-apollo-1.7.1-unix-distro.tar.gz
- 创建broker
-
cd ./apache-apollo-1.7.1/bin/
apollo create apollo_broker
-
- 修改配置，允许指定主机访问web管理控制台
- apollo_broker/etc/apollo.xml文件，不绑定回送地址127.0.0.1
- apollo_broker/etc/login.config文件，添加白名单文件
- 添加允许以下主机访问web控制台
- apollo_broker/etc/apollo.xml文件，不绑定回送地址127.0.0.1
- 运行broker
- apollo_broker/bin/apollo-broker run
- apollo_broker/bin/apollo-broker run
- ip地址
- 访问web控制台
- 初始账号：admin，密码：password
- 登入成功
- 初始账号：admin，密码：password
五、SpringBoot 创建发送者，接受者
参考：apache-apollo-X.X.X/examples目录中，自带了demo
创建spring boot project
发送者的springboot项目 ----》 Publisher
接受者的springboot项目 ----》 Listener
pom.xml
<dependency>
<groupId>org.fusesource.mqtt-client</groupId>
<artifactId>mqtt-client</artifactId>
<version>1.0</version>
</dependency>
<dependency>
<groupId>org.eclipse.paho</groupId>
<artifactId>org.eclipse.paho.client.mqttv3</artifactId>
<version>1.2.0</version>
</dependency>
发送者
Listener.java
/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 example;
import org.fusesource.hawtbuf.AsciiBuffer;
import org.fusesource.hawtbuf.Buffer;
import org.fusesource.hawtbuf.UTF8Buffer;
import org.fusesource.mqtt.client.Future;
import org.fusesource.mqtt.client.FutureConnection;
import org.fusesource.mqtt.client.MQTT;
import org.fusesource.mqtt.client.QoS;
import java.util.LinkedList;
/**
* Uses a Future based API to MQTT.
*/
class Publisher {
public static void main(String []args) throws Exception {
String user = env("APOLLO_USER", "admin");
String password = env("APOLLO_PASSWORD", "password");
String host = env("APOLLO_HOST", "localhost");
int port = Integer.parseInt(env("APOLLO_PORT", "61613"));
final String destination = arg(args, 0, "/topic/event");
int messages = 10000;
int size = 256;
String DATA = "abcdefghijklmnopqrstuvwxyz";
String body = "";
for( int i=0; i < size; i ++) {
body += DATA.charAt(i%DATA.length());
}
Buffer msg = new AsciiBuffer(body);
MQTT mqtt = new MQTT();
mqtt.setHost(host, port);
mqtt.setUserName(user);
mqtt.setPassword(password);
FutureConnection connection = mqtt.futureConnection();
connection.connect().await();
final LinkedList<Future<Void>> queue = new LinkedList<Future<Void>>();
UTF8Buffer topic = new UTF8Buffer(destination);
for( int i=1; i <= messages; i ++) {
// Send the publish without waiting for it to complete. This allows us
// to send multiple message without blocking..
queue.add(connection.publish(topic, msg, QoS.AT_LEAST_ONCE, false));
// Eventually we start waiting for old publish futures to complete
// so that we don't create a large in memory buffer of outgoing message.s
if( queue.size() >= 1000 ) {
queue.removeFirst().await();
}
}
queue.add(connection.publish(topic, new AsciiBuffer("SHUTDOWN"), QoS.AT_LEAST_ONCE, false));
while( !queue.isEmpty() ) {
queue.removeFirst().await();
}
connection.disconnect().await();
System.exit(0);
}
private static String env(String key, String defaultValue) {
String rc = System.getenv(key);
if( rc== null )
return defaultValue;
return rc;
}
private static String arg(String []args, int index, String defaultValue) {
if( index < args.length )
return args[index];
else
return defaultValue;
}
}
接受者
Listener.java
/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 example;
import org.fusesource.hawtbuf.*;
import org.fusesource.mqtt.client.*;
/**
* Uses an callback based interface to MQTT. Callback based interfaces
* are harder to use but are slightly more efficient.
*/
class Listener {
public static void main(String []args) throws Exception {
String user = env("APOLLO_USER", "admin");
String password = env("APOLLO_PASSWORD", "password");
String host = env("APOLLO_HOST", "localhost");
int port = Integer.parseInt(env("APOLLO_PORT", "61613"));
final String destination = arg(args, 0, "/topic/event");
MQTT mqtt = new MQTT();
mqtt.setHost(host, port);
mqtt.setUserName(user);
mqtt.setPassword(password);
final CallbackConnection connection = mqtt.callbackConnection();
connection.listener(new org.fusesource.mqtt.client.Listener() {
long count = 0;
long start = System.currentTimeMillis();
public void onConnected() {
}
public void onDisconnected() {
}
public void onFailure(Throwable value) {
value.printStackTrace();
System.exit(-2);
}
public void onPublish(UTF8Buffer topic, Buffer msg, Runnable ack) {
String body = msg.utf8().toString();
if( "SHUTDOWN".equals(body)) {
long diff = System.currentTimeMillis() - start;
System.out.println(String.format("Received %d in %.2f seconds", count, (1.0*diff/1000.0)));
connection.disconnect(new Callback<Void>() {
@Override
public void onSuccess(Void value) {
System.exit(0);
}
@Override
public void onFailure(Throwable value) {
value.printStackTrace();
System.exit(-2);
}
});
} else {
if( count == 0 ) {
start = System.currentTimeMillis();
}
if( count % 1000 == 0 ) {
System.out.println(String.format("Received %d messages.", count));
}
count ++;
}
}
});
connection.connect(new Callback<Void>() {
@Override
public void onSuccess(Void value) {
Topic[] topics = {new Topic(destination, QoS.AT_LEAST_ONCE)};
connection.subscribe(topics, new Callback<byte[]>() {
public void onSuccess(byte[] qoses) {
}
public void onFailure(Throwable value) {
value.printStackTrace();
System.exit(-2);
}
});
}
@Override
public void onFailure(Throwable value) {
value.printStackTrace();
System.exit(-2);
}
});
// Wait forever..
synchronized (Listener.class) {
while(true)
Listener.class.wait();
}
}
private static String env(String key, String defaultValue) {
String rc = System.getenv(key);
if( rc== null )
return defaultValue;
return rc;
}
private static String arg(String []args, int index, String defaultValue) {
if( index < args.length )
return args[index];
else
return defaultValue;
}
}
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