MQTT发送和接收HEX数据

import static org.fusesource.hawtbuf.Buffer.utf8;

import java.nio.ByteBuffer;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;

import org.fusesource.mqtt.client.BlockingConnection;
import org.fusesource.mqtt.client.MQTT;
import org.fusesource.mqtt.client.Message;
import org.fusesource.mqtt.client.QoS;
import org.fusesource.mqtt.client.Topic;
public class MqttUtil {
    public static void test(String topic) throws Exception {
            Map<String, Object> jsonMap = new HashMap<String, Object>();
            MQTT mqtt = new MQTT();
            //mqtt连接地址
            mqtt.setHost(server_addr, port);
            // mqtt.setClientId(clientId);
            mqtt.setCleanSession(true);
            //mqtt 用户名
            mqtt.setUserName(username);
            //mqtt 密码
            mqtt.setPassword(password);
            //16进制字符串转换为Byte型数组
            byte[] payload = HexStringToByte("48454C4C4F");
             //byte[] payload = {(byte) 0xF0, (byte) 0x9F, (byte) 0x98, (byte) 0x81};
            //获取mqtt的连接对象BlockingConnection
            BlockingConnection connection = mqtt.blockingConnection();
            //连接mqtt
            connection.connect();
            //mq主题
            Topic[] topics = { new Topic(utf8(topic), QoS.AT_LEAST_ONCE) };
            //订阅主题
            byte[] qoses = connection.subscribe(topics);
            //发送消息
            connection.publish(topic, payload, QoS.EXACTLY_ONCE, false);
            
            //接收主题消息
            Message message;
            while (true) {
                try {
                    message = connection.receive(1000, TimeUnit.MILLISECONDS);
                    System.out.println("1--"+new String(message.getPayload()));
                    //接收消息
                    String msg = String.valueOf(message.getPayloadBuffer());
                    System.out.println("2--"+msg);
                    String jsonStr = "";
                    //判断是消息体是ASCII还是HEX
                    if (msg.substring(0, 3).equals("hex")) {
                        msg = msg.substring(5);
                        byte[] bytes = HexStringToByte(msg);
                        jsonStr = new String(bytes, "utf-8");
                        System.out.println("3--"+jsonStr);
                    } else {
                        jsonStr = msg.substring(7);
                        System.out.println(jsonStr);
                    }
                } catch (Exception e) {
                    connection.disconnect();
                    break;
                }
            }
        }

/**
     * 16进制字符串转换为Byte型数组16进制源字符串
     * 
     * @param 16进制字符串
     * @return Byte类型数组
     */
    public static byte[] HexStringToByte(String hexString) {
        hexString = hexString.replace(" ", "");
        int len = hexString.length();
        if (len % 2 != 0)
            return null;
        byte[] bufD = new byte[len / 2];
        byte[] tmpBuf = hexString.getBytes();
        int i = 0, j = 0;
        for (i = 0; i < len; i++) {
            if (tmpBuf[i] >= 0x30 && tmpBuf[i] <= 0x39)
                tmpBuf[i] -= 0x30;
            else if (tmpBuf[i] >= 0x41 && tmpBuf[i] <= 0x46)
                tmpBuf[i] -= 0x37;
            else if (tmpBuf[i] >= 0x61 && tmpBuf[i] <= 0x66)
                tmpBuf[i] -= 0x57;
            else
                tmpBuf[i] = 0xF;
        }
        for (i = 0, j = 0; i < len; i += 2, j++) {
            bufD[j] = (byte) ((tmpBuf[i] << 4) | tmpBuf[i + 1]);
        }
        return bufD;

    }

    public static void main(String[] args) throws Exception {
        test("myTopic");
    }



}