rabbitmq作为mqtt服务器实现websocket消息推送给浏览器

rabbitmq的RabbitMQ Web MQTT插件可以用来支持将rabbitmq作为MQTT协议的服务器，而websocket支持mqtt协议通信实现消息推送。因为我们目前使用rabbitmq，所以采用其作为ws的服务端（原来有过activemq的做法，其原生也支持MQTT协议）。

首先安装RabbitMQ Web MQTT插件，如下：

rabbitmq-plugins enable rabbitmq_web_mqtt

MQTT在15675端口下的ws命名空间暴露WebSocket端点。如下：

http://IP:15675/ws

Eclipse旗下的Paho JavaScript客户端可以使用MQTT协议实现ws通信，其使用如下：

<script src="mqttws31.js"></script>
<script>

    var wsbroker = location.hostname;  // mqtt websocket enabled broker
    var wsport = 15675; // port for above
    client = new Paho.MQTT.Client(wsbroker, wsport, "/ws",
        "myclientid_" + parseInt(Math.random() * 100, 10));
    client.onConnectionLost = function (responseObject) {
        debug("CONNECTION LOST - " + responseObject.errorMessage);
    };
    client.onMessageArrived = function (message) {
        debug("RECEIVE ON " + message.destinationName + " PAYLOAD " + message.payloadString);
        print_first(message.payloadString);
    };
var sessionId = getSessionId();
var options = {
    timeout: 3,
    keepAliveInterval: 30,
    onSuccess: function () {
        debug("CONNECTION SUCCESS");
        // 这样就可以做到点对点通信
        client.subscribe(sessionId, {qos: 1});
    },
    onFailure: function (message) {
        debug("CONNECTION FAILURE - " + message.errorMessage);
    }
};
if (location.protocol == "https:") {
    options.useSSL = true;
}
debug("CONNECT TO " + wsbroker + ":" + wsport);
client.connect(options);

java服务端发送消息给rabbitmq：

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
private static void testSendMqtt() throws IOException, TimeoutException {
        ConnectionFactory factory = new ConnectionFactory();
        factory.setUsername("guest");
        factory.setPassword("guest");
        // factory.setVirtualHost("");
        factory.setHost("127.0.0.1");
        factory.setPort(5672);
        Connection conn = null;
        Channel channel = null;
        try {
            conn = factory.newConnection();
            channel = conn.createChannel();
            String sessionId = getSessionId();
            byte[] messageBodyBytes = "{'text':'Hello, world!中文'}".getBytes();
            // 这样就可以做到点对点通信了，amq.topic是默认exchange
            channel.basicPublish("amq.topic", sessionId, null, messageBodyBytes);
        }finally {
            if (channel != null) {
                channel.close();
            }
            if (conn != null) {
                conn.close();
            }
        }
    }

参考：

https://www.rabbitmq.com/web-mqtt.html

https://www.eclipse.org/paho/clients/js/