MQTT MqttException 128错误

今天遇到MQTT连接，抛出128错误，最后经过排查，竟然是订阅主题错误。

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2019-9-4 补充

因为当初项目里面使用的时候亚马逊封装的MQTT，当初对MQTT异常信息了解的不多，最近公司项目使用的是原生的MQTT开源项目，通过阅读源码，进一步学习了MQTT异常信息的解读。

package org.eclipse.paho.client.mqttv3;

import org.eclipse.paho.client.mqttv3.internal.MessageCatalog;

/**
 * Thrown if an error occurs communicating with the server.
 */
public class MqttException extends Exception {
	private static final long serialVersionUID = 300L;
	
	/** 
	 * Client encountered an exception.  Use the {@link #getCause()}
	 * method to get the underlying reason.
	 */
	public static final short REASON_CODE_CLIENT_EXCEPTION              = 0x00;

	// CONNACK return codes
	/** 
	*The protocol version requested is not supported by the server. 
	*请求协议版本服务端不支持
	*/
	public static final short REASON_CODE_INVALID_PROTOCOL_VERSION		= 0x01;
	/** 
	*The server has rejected the supplied client ID 
	*服务端拒绝客户端ID
	*/
	public static final short REASON_CODE_INVALID_CLIENT_ID      		= 0x02;
	/** 
	*The broker was not available to handle the request.
	*
	 */
	public static final short REASON_CODE_BROKER_UNAVAILABLE             = 0x03;
	/** 
	*Authentication with the server has failed, due to a bad user name or password. 
	*因为错误的用户名或则密码，服务端认证失败
	*/
	public static final short REASON_CODE_FAILED_AUTHENTICATION			= 0x04; 
	/** 
	*Not authorized to perform the requested operation 
	*
	*/
	public static final short REASON_CODE_NOT_AUTHORIZED				= 0x05;

	/** An unexpected error has occurred. */
	public static final short REASON_CODE_UNEXPECTED_ERROR				= 0x06;
	
	/** 
	* Error from subscribe - returned from the server. 
	* 异常源于订阅 0x80的十进制就是128，和当初排查出来的原因是一样的
	*/
	public static final short REASON_CODE_SUBSCRIBE_FAILED				= 0x80;
	
	/** 
	 * Client timed out while waiting for a response from the server.
	 * The server is no longer responding to keep-alive messages.
	 * 客户端等待服务器响应超时
	 */
	public static final short REASON_CODE_CLIENT_TIMEOUT                = 32000;

	/**
	 * Internal error, caused by no new message IDs being available.
	 */
	public static final short REASON_CODE_NO_MESSAGE_IDS_AVAILABLE      = 32001;

	/** 
	 * Client timed out while waiting to write messages to the server.
	 * 客户端向服务器写入数据超时
	 */
	public static final short REASON_CODE_WRITE_TIMEOUT                 = 32002;
	
	/**
	 * The client is already connected.
	 * 客户端已连接服务器
	 */
	public static final short REASON_CODE_CLIENT_CONNECTED              = 32100;

	/**
	 * The client is already disconnected.
	 * 客户端已断开服务器（出现场景：当客户端已断开服务器时，还订阅主题或则发布消息时，会抛出此异常）
	 */
	public static final short REASON_CODE_CLIENT_ALREADY_DISCONNECTED   = 32101;
	/** 
	 * The client is currently disconnecting and cannot accept any new work.
	 * This can occur when waiting on a token, and then disconnecting the client.  
	 * If the message delivery does not complete within the quiesce timeout 
	 * period, then the waiting token will be notified with an exception.
	 * 客户端正在断开，不能接受任何连接
	 */
	public static final short REASON_CODE_CLIENT_DISCONNECTING          = 32102;
	
	/** 
	*Unable to connect to server 
	*客户端无法连接服务端
	*/
	public static final short REASON_CODE_SERVER_CONNECT_ERROR          = 32103;

	/** 
	 * The client is not connected to the server.  The {@link MqttClient#connect()}
	 * or {@link MqttClient#connect(MqttConnectOptions)} method must be called
	 * first.  It is also possible that the connection was lost - see 
	 * {@link MqttClient#setCallback(MqttCallback)} for a way to track lost
	 * connections.  
	 * 客户端没有连接服务端
	 */
	public static final short REASON_CODE_CLIENT_NOT_CONNECTED          = 32104;

	/** 
	 * Server URI and supplied SocketFactory do not match.
	 * URIs beginning tcp:// must use a javax.net.SocketFactory,
	 * and URIs beginning ssl:// must use a javax.net.ssl.SSLSocketFactory.
	 * 服务端的URI和提供的SocketFactory不匹配
	 */
	public static final short REASON_CODE_SOCKET_FACTORY_MISMATCH       = 32105;
	
	/**
	 * SSL configuration error.
	 */
	public static final short REASON_CODE_SSL_CONFIG_ERROR              = 32106;

	/** 
	 * Thrown when an attempt to call {@link MqttClient#disconnect()} has been 
	 * made from within a method on {@link MqttCallback}.  These methods are invoked
	 * by the client's thread, and must not be used to control disconnection.
	 * 
	 * @see MqttCallback#messageArrived(String, MqttMessage)
	 */
	public static final short REASON_CODE_CLIENT_DISCONNECT_PROHIBITED  = 32107;

	/** 
	 * Protocol error: the message was not recognized as a valid MQTT packet.
	 * Possible reasons for this include connecting to a non-MQTT server, or
	 * connecting to an SSL server port when the client isn't using SSL.
	 */
	public static final short REASON_CODE_INVALID_MESSAGE				= 32108;

	/**
	 * The client has been unexpectedly disconnected from the server. The {@link #getCause() cause}
	 * will provide more details. 
	 */
	public static final short REASON_CODE_CONNECTION_LOST               = 32109;
	
	/**
	 * A connect operation in already in progress, only one connect can happen
	 * at a time.
	 * 只允许一个连接
	 */
	public static final short REASON_CODE_CONNECT_IN_PROGRESS           = 32110;
	
	/**
	 * The client is closed - no operations are permitted on the client in this
	 * state.  New up a new client to continue.
	 */
	public static final short REASON_CODE_CLIENT_CLOSED		           = 32111;
	
	/**
	 * A request has been made to use a token that is already associated with
	 * another action.  If the action is complete the reset() can ve called on the
	 * token to allow it to be reused.  
	 */
	public static final short REASON_CODE_TOKEN_INUSE		           = 32201;
	
	/**
	 * A request has been made to send a message but the maximum number of inflight 
	 * messages has already been reached. Once one or more messages have been moved
	 * then new messages can be sent.   
	 */
	public static final short REASON_CODE_MAX_INFLIGHT    			= 32202;
	
	/**
	 * The Client has attempted to publish a message whilst in the 'resting' / offline
	 * state with Disconnected Publishing enabled, however the buffer is full and
	 * deleteOldestMessages is disabled, therefore no more messages can be published
	 * until the client reconnects, or the application deletes buffered message
	 * manually. 
	 */
	public static final short REASON_CODE_DISCONNECTED_BUFFER_FULL	= 32203;

	private int reasonCode;
	private Throwable cause;
	
	/**
	 * Constructs a new MqttException with the specified code
	 * as the underlying reason.
	 * @param reasonCode the reason code for the exception.
	 */
	public MqttException(int reasonCode) {
		super();
		this.reasonCode = reasonCode;
	}
	
	/**
	 * Constructs a new MqttException with the specified 
	 * Throwable as the underlying reason.
	 * @param cause the underlying cause of the exception.
	 */
	public MqttException(Throwable cause) {
		super();
		this.reasonCode = REASON_CODE_CLIENT_EXCEPTION;
		this.cause = cause;
	}

	/**
	 * Constructs a new MqttException with the specified 
	 * Throwable as the underlying reason.
	 * @param reason the reason code for the exception.
	 * @param cause the underlying cause of the exception.
	 */
	public MqttException(int reason, Throwable cause) {
		super();
		this.reasonCode = reason;
		this.cause = cause;
	}

	
	/**
	 * Returns the reason code for this exception.
	 * @return the code representing the reason for this exception.
	 */
	public int getReasonCode() {
		return reasonCode;
	}
	
	/**
	 * Returns the underlying cause of this exception, if available.
	 * @return the Throwable that was the root cause of this exception,
	 * which may be null.
	 */
	public Throwable getCause() {
		return cause;
	}
	
	/**
	 * Returns the detail message for this exception.
	 * @return the detail message, which may be null.
	 */
	public String getMessage() {
		return MessageCatalog.getMessage(reasonCode);
	}
	
	/**
	 * Returns a String representation of this exception.
	 * @return a String representation of this exception.
	 */
	public String toString() {
		String result = getMessage() + " (" + reasonCode + ")";
		if (cause != null) {
			result = result + " - " + cause.toString();
		}
		return result;
	}
}