{"id":463,"date":"2015-09-08T15:19:22","date_gmt":"2015-09-08T15:19:22","guid":{"rendered":"428fca9bc1921c25c5121f9da7815cde"},"modified":"2015-09-08T15:19:22","modified_gmt":"2015-09-08T15:19:22","slug":"","status":"publish","type":"post","link":"https:\/\/www.xiaobo.li\/notes\/archives\/463","title":{"rendered":"\u56db.MQTT\u534f\u8bae\u7b14\u8bb0\u4e4b\u6d88\u606f\u6d41"},"content":{"rendered":"

\u524d\u8a00<\/strong><\/p>\n

\u524d\u9762\u7684\u7b14\u8bb0\u5df2\u628a\u6240\u6709\u6d88\u606f\u7c7b\u578b\u90fd\u8fc7\u4e86\u4e00\u904d\uff0c\u8fd9\u91cc\u4ece\u6d88\u606f\u6d41\u7684\u89d2\u5ea6\u5c1d\u8bd5\u89e3\u8bfb\u4e00\u4e0b\u3002<\/p>\n

\u7f51\u7edc\u6545\u969c<\/h3>\n

\u5728\u4efb\u4f55\u7f51\u7edc\u73af\u5883\u4e0b\uff0c\u90fd\u4f1a\u51fa\u73b0\u4e00\u65b9\u8fde\u63a5\u5931\u8d25\uff0c\u6bd4\u5982\u79bb\u5f00\u516c\u53f8\u5927\u95e8\u90a3\u4e00\u523b\u6ca1\u6709\u4e86WIFI\u4fe1\u53f7\u3002\u4f46\u6301\u7eed\u8fde\u63a5\u7684\u53e6\u4e00\u7aef-\u670d\u52a1\u5668\u53ef\u80fd\u4e0d\u80fd\u7acb\u5373\u77e5\u9053\u5bf9\u65b9\u5df2\u65ad\u5f00\u3002\u7c7b\u4f3c\u7f51\u7edc\u5f02\u5e38\u60c5\u51b5\uff0c\u90fd\u6709\u53ef\u80fd\u5728\u6d88\u606f\u53d1\u9001\u7684\u8fc7\u7a0b\u4e2d\u51fa\u73b0\uff0c\u6d88\u606f\u53d1\u9001\u51fa\u53bb\uff0c\u5c31\u4e22\u5931\u4e86\u3002<\/p>\n

MQTT\u534f\u8bae\u5047\u5b9a\u5ba2\u6237\u7aef\u548c\u670d\u52a1\u5668\u7aef\u7a33\u5b9a\u60c5\u51b5\u4e00\u822c\uff0c\u5f7c\u6b64\u4e4b\u901a\u4fe1\u7ba1\u9053\u4e0d\u53ef\u9760\uff0c\u4e00\u65e6\u5ba2\u6237\u7aef\u7f51\u7edc\u65ad\u5f00\uff0c\u60c5\u51b5\u5c31\u4f1a\u5f88\u4e25\u91cd\uff0c\u5f88\u96be\u6062\u590d\u539f\u72b6\u3002<\/p>\n

\u4f46\u522b\u5fd8\u8bb0\uff0c\u5f88\u591a\u5ba2\u6237\u7aef\u4f1a\u6709\u6c38\u4e45\u6027\u5b58\u50a8\u8bbe\u5907\u652f\u6301\uff0c\u6bd4\u5982\u95ea\u5b58ROM\u3001\u5b58\u50a8\u5361\u7b49\uff0c\u5728\u901a\u4fe1\u51fa\u73b0\u5f02\u5e38\u7684\u60c5\u51b5\u4e0b\u53ef\u4ee5\u7528\u4e8e\u4fdd\u5b58\u5173\u952e\u6570\u636e\u6216\u72b6\u6001\u4fe1\u606f\u7b49\u3002<\/p>\n

\u603b\u4e4b\uff0c\u5f02\u5e38\u7f51\u7edc\u60c5\u51b5\u5f88\u590d\u6742\uff0c\u53ea\u80fd\u5c0f\u5fc3\u5904\u7406\u4e4b\u3002<\/p>\n

\u6d88\u606f\u91cd\u53d1\u7b56\u7565<\/h3>\n

\u5728QoS > 0<\/strong>\u60c5\u51b5\u4e0b\uff0cPUBLISH\u3001PUBREL\u3001SUBSCRIBE\u3001UNSUBSCRIBE\u7b49\u7c7b\u578b\u6d88\u606f\u5728\u53d1\u9001\u8005\u53d1\u9001\u5b8c\u4e4b\u540e\uff0c\u9700\u8981\u7b49\u5f85\u4e00\u4e2a\u54cd\u5e94\u6d88\u606f\uff0c\u82e5\u5728\u4e00\u4e2a\u6307\u5b9a\u65f6\u95f4\u6bb5\u5185\u6ca1\u6709\u6536\u5230\uff0c\u53d1\u9001\u8005\u53ef\u80fd\u9700\u8981\u91cd\u8bd5\u3002\u91cd\u53d1\u7684\u6d88\u606f\uff0c\u8981\u6c42DUP\u6807\u8bb0\u8981\u8bbe\u7f6e\u4e3a1.<\/p>\n

\u7b49\u5f85\u54cd\u5e94\u7684\u8d85\u65f6\u5e94\u8be5\u5728\u6d88\u606f\u6210\u529f\u53d1\u9001\u4e4b\u540e\u5f00\u59cb\u7b97\u8d77\uff0c\u5e76\u4e14\u7b49\u5f85\u8d85\u65f6\u5e94\u8be5\u662f\u53ef\u4ee5\u914d\u7f6e\u9009\u9879\uff0c\u4ee5\u4fbf\u5728\u4e0b\u4e00\u6b21\u91cd\u8bd5\u7684\u65f6\u5019\uff0c\u9002\u5f53\u52a0\u5927\u3002\u6bd4\u5982\u7b2c\u4e00\u6b21\u91cd\u8bd5\u8d85\u65f610\u79d2\uff0c\u4e0b\u4e00\u6b21\u53ef\u80fd\u4e3a20\u79d2\uff0c\u518d\u4e00\u6b21\u91cd\u8bd5\u53ef\u80fd\u4e3a60\u79d2\u5462\u3002\u5f53\u7136\uff0c\u8fd8\u8981\u6709\u4e00\u4e2a\u91cd\u8bd5\u6b21\u6570\u9650\u5236\u7684\u3002<\/p>\n

\u8fd8\u6709\u4e00\u79cd\u60c5\u51b5\uff0c\u5ba2\u6237\u7aef\u91cd\u65b0\u8fde\u63a5\uff0c\u4f46\u672a\u5728\u53ef\u53d8\u5934\u90e8\u4e2d\u8bbe\u7f6eclean session\u6807\u8bb0\uff0c\u4f46\u53cc\u65b9(\u5ba2\u6237\u7aef\u548c\u670d\u52a1\u5668\u7aef)\u90fd\u5e94\u8be5\u91cd\u8bd5\u5148\u524d\u672a\u53d1\u9001\u7684\u52a8\u6001\u6d88\u606f\uff08in-flight messages\uff09\u3002\u5ba2\u6237\u7aef\u4e0d\u88ab\u5f3a\u5236\u8981\u6c42\u53d1\u9001\u672a\u88ab\u786e\u8ba4\u7684\u6d88\u606f\uff0c\u4f46\u670d\u52a1\u5668\u7aef\u5c31\u5f97\u9700\u8981\u91cd\u53d1\u90a3\u4e9b\u672a\u88ab\u53bb\u786e\u8ba4\u7684\u6d88\u606f\u3002<\/p>\n

QoS level\u51b3\u5b9a\u7684\u6d88\u606f\u6d41<\/h4>\n

QoS level\u4e3aQuality of Service level\u7684\u7f29\u5199\uff0c\u7ffb\u8bd1\u6210\u4e2d\u6587\uff0c\u670d\u52a1\u8d28\u91cf\u7b49\u7ea7\u3002<\/p>\n

MQTT 3.1\u534f\u8bae\u5728\"4.1 Quality of Service levels and flows\"\u7ae0\u8282\u4e2d\uff0c\u4ec5\u4ec5\u8ba8\u8bba\u4e86\u5ba2\u6237\u7aef\u5230\u670d\u52a1\u5668\u7684\u53d1\u5e03\u6d41\u7a0b\uff0c\u4e0d\u592a\u5b8c\u6574\u3002\u56e0\u4e3a\u51b3\u5b9a\u6d88\u606f\u5230\u8fbe\u7387\uff0c\u80fd\u591f\u63d0\u5347\u53d1\u9001\u8d28\u91cf\u7684\uff0c\u5e94\u8be5\u662f\u670d\u52a1\u5668\u53d1\u5e03PUBLISH\u6d88\u606f\u5230\u8ba2\u9605\u8005\u8fd9\u4e00\u6d88\u606f\u6d41\u65b9\u5411\u3002<\/p>\n

QoS level 0<\/h4>\n

\u81f3\u591a\u53d1\u9001\u4e00\u6b21\uff0c\u53d1\u9001\u5373\u4e22\u5f03\u3002\u6ca1\u6709\u786e\u8ba4\u6d88\u606f\uff0c\u4e5f\u4e0d\u77e5\u9053\u5bf9\u65b9\u662f\u5426\u6536\u5230\u3002<\/p>\n\n\n\n\n\n
Client<\/th>\nMessage and direction<\/th>\nServer<\/th>\n<\/tr>\n<\/thead>\n
QoS = 0<\/td>\nPUBLISH <\/span>

\n----------><\/code><\/td>\n		Action:<\/strong> <\/span>Publish message to subscribers then Forget
\nReception: <\/span><\/strong><=1<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\u9488\u5bf9\u7684\u6d88\u606f\u4e0d\u91cd\u8981\uff0c\u4e22\u5931\u4e5f\u65e0\u6240\u8c13\u3002<\/p>\n

\u7f51\u7edc\u5c42\u9762\uff0c\u4f20\u8f93\u538b\u529b\u5c0f\u3002<\/p>\n

QoS level 1<\/h4>\n

\u6240\u6709QoS level 1\u90fd\u8981\u5728\u53ef\u53d8\u5934\u90e8\u4e2d\u9644\u52a0\u4e00\u4e2a16\u4f4d\u7684\u6d88\u606fID\u3002<\/p>\n

SUBSCRIBE\u548cUNSUBSCRIBE\u6d88\u606f\u4f7f\u7528QoS level 1\u3002<\/p>\n

\u9488\u5bf9\u6d88\u606f\u7684\u53d1\u5e03\uff0cQos level 1<\/strong>\uff0c\u610f\u5473\u7740\u6d88\u606f\u81f3\u5c11\u88ab\u4f20\u8f93\u4e00\u6b21\u3002<\/p>\n

\u53d1\u9001\u8005\u82e5\u5728\u4e00\u6bb5\u65f6\u95f4\u5185\u63a5\u6536\u4e0d\u5230PUBACK\u6d88\u606f\uff0c\u53d1\u9001\u8005\u9700\u8981\u6253\u5f00DUB\u6807\u8bb0\u4e3a1\uff0c\u7136\u540e\u91cd\u65b0\u53d1\u9001PUBLISH\u6d88\u606f\u3002\u56e0\u6b64\u4f1a\u5bfc\u81f4\u63a5\u6536\u65b9\u53ef\u80fd\u4f1a\u6536\u5230\u4e24\u6b21PUBLISH\u6d88\u606f\u3002\u9488\u5bf9\u5ba2\u6237\u7aef\u53d1\u5e03\u6d88\u606f\u5230\u670d\u52a1\u5668\u7684\u6d88\u606f\u6d41\uff1a<\/p>\n\n\n\n\n\n\n
Client<\/th>\nMessage and direction<\/th>\nServer<\/th>\n<\/tr>\n<\/thead>\n
QoS = 1

\nDUP = 0
\nMessage ID = x<\/p>\n

Action:<\/strong> <\/span>Store message<\/p>\n<\/td>\n

PUBLISH <\/span>

\n----------><\/code><\/td>\n		\n
Actions:<\/strong> <\/p>\n
    \n
  • \n

    Store message<\/p>\n<\/li>\n

  • Publish message to subscribers<\/li>\n
  • \n

    Delete message<\/p>\n<\/li>\n<\/ul>\n<\/div>\n

    Reception: <\/span><\/strong>>=1<\/div>\n<\/td>\n<\/tr>\n
Action:<\/strong> <\/span>Discard message<\/td>\nPUBACK <\/span>

\n<----------<\/code><\/td>\n		\n
Message ID = x<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\u9488\u5bf9\u670d\u52a1\u5668\u53d1\u5e03\u5230\u8ba2\u9605\u8005\u7684\u6d88\u606f\u6d41\uff1a<\/p>\n\n\n\n\n\n\n
Server<\/th>\nMessage and direction<\/th>\nSubscriber<\/th>\n<\/tr>\n<\/thead>\n
QoS = 1

\nDUP = 0

\nMessage ID = x<\/td>\n		PUBLISH <\/span>

\n----------><\/code><\/td>\n		\n
Actions:<\/strong> <\/p>\n
    \n
  • \n

    Store message<\/p>\n<\/li>\n

  • Make message available                       <\/li>\n<\/ul>\n<\/div>\n
    Reception: <\/span><\/strong>>=1<\/div>\n<\/td>\n<\/tr>\n


\n<\/strong><\/td>\n		PUBACK <\/span>

\n<----------<\/code><\/td>\n		\n
Message ID = x<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\u53d1\u5e03\u8005\uff08\u5ba2\u6237\u7aef\/\u670d\u52a1\u5668\uff09\u82e5\u56e0\u79cd\u79cd\u5f02\u5e38\u63a5\u6536\u4e0d\u5230PUBACK\u6d88\u606f\uff0c\u4f1a\u518d\u6b21\u91cd\u65b0\u53d1\u9001PUBLISH\u6d88\u606f\uff0c\u540c\u65f6\u8bbe\u7f6eDUP\u6807\u8bb0\u4e3a1\u3002\u63a5\u6536\u8005\u4ee5\u670d\u52a1\u5668\u4e3a\u4f8b\uff0c\u8fd9\u53ef\u80fd\u4f1a\u5bfc\u81f4\u670d\u52a1\u5668\u6536\u5230\u91cd\u590d\u6d88\u606f\uff0c\u6309\u7167\u6d41\u7a0b\uff0cbroker\uff08\u670d\u52a1\u5668\uff09\u53d1\u5e03\u6d88\u606f\u5230\u8ba2\u9605\u8005\uff08\u4f1a\u5bfc\u81f4\u8ba2\u9605\u8005\u63a5\u6536\u5230\u91cd\u590d\u6d88\u606f\uff09\uff0c\u7136\u540e\u53d1\u9001\u4e00\u6761PUBACK\u786e\u8ba4\u6d88\u606f\u5230\u53d1\u5e03\u8005\u3002<\/p>\n

\u5728\u4e1a\u52a1\u5c42\u9762\uff0c\u6216\u8bb8\u53ef\u4ee5\u5f25\u8865MQTT\u534f\u8bae\u7684\u4e0d\u8db3\u4e4b\u5904\uff1a\u91cd\u8bd5\u7684\u6d88\u606fID\u4e00\u5b9a\u8981\u4e00\u81f4\u63a5\u6536\u65b9\u4e00\u5b9a\u5224\u65ad\u5f53\u524d\u63a5\u6536\u7684\u6d88\u606fID\u662f\u5426\u5df2\u7ecf\u63a5\u53d7\u8fc7<\/p>\n

\u4f46\u4e00\u6837\u4e0d\u80fd\u591f\u5b8c\u5168\u786e\u4fdd\uff0c\u6d88\u606f\u4e00\u5b9a\u5230\u8fbe\u4e86\u3002<\/p>\n

QoS level 2<\/h4>\n

\u4ec5\u4ec5\u5728PUBLISH\u7c7b\u578b\u6d88\u606f\u4e2d\u51fa\u73b0\uff0c\u8981\u6c42\u5728\u53ef\u53d8\u5934\u90e8\u4e2d\u8981\u9644\u52a0\u6d88\u606fID\u3002<\/p>\n

\u7ea7\u522b\u9ad8\uff0c\u901a\u4fe1\u538b\u529b\u7a0d\u5927\u4e9b\uff0c\u4f46\u786e\u4fdd\u4e86\u4ec5\u4ec5\u4f20\u8f93\u63a5\u6536\u4e00\u6b21\u3002<\/p>\n

\u5148\u770b\u534f\u8bae\u4e2d\u6d41\u7a0b\u56fe\uff0cClient -> Server\u65b9\u5411\uff0c\u4f1a\u6709\u4e00\u4e2a\u603b\u4f53\u5370\u8c61\uff1a<\/p>\n\n\n\n\n\n\n\n\n
Client<\/th>\nMessage and direction<\/th>\nServer<\/th>\n<\/tr>\n<\/thead>\n
QoS = 2

\nDUP = 0
\nMessage ID = x<\/p>\n

Action:<\/strong> <\/span>Store message<\/p>\n<\/td>\n

PUBLISH <\/span>

\n----------><\/code><\/td>\n		Action(a)<\/strong> <\/span>Store message<\/p>\n

or<\/em><\/p>\n

Actions(b):<\/strong> <\/p>\n

    \n
  • Store message ID<\/li>\n
  • Publish message to subscribers<\/li>\n<\/ul>\n<\/td>\n<\/tr>\n
 <\/td>\nPUBREC <\/span>

\n<----------<\/code><\/td>\n		Message ID = x<\/td>\n<\/tr>\n
Message ID = x<\/td>\nPUBREL <\/span>

\n----------><\/code><\/td>\n		Actions(a):<\/strong> <\/p>\n
    \n
  • Publish message to subscribers<\/li>\n
  • Delete message<\/li>\n<\/ul>\n

    or<\/em><\/p>\n

    Action(b):<\/strong> <\/span>Delete message ID<\/td>\n<\/tr>\n

Action:<\/strong> <\/span>Discard message<\/td>\nPUBCOMP <\/span>

\n<----------<\/code><\/td>\n		Message ID = x<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Server -> Subscriber<\/strong>\uff1a<\/p>\n\n\n\n\n\n\n\n\n
Server<\/th>\nMessage and direction<\/th>\nSubscriber<\/th>\n<\/tr>\n<\/thead>\n
QoS = 2

\nDUP = 0

\nMessage ID = x<\/td>\n		PUBLISH <\/span>

\n----------><\/code><\/td>\n		Action:<\/strong> <\/span>Store message<\/td>\n<\/tr>\n
 <\/td>\nPUBREC <\/span>

\n<----------<\/code><\/td>\n		Message ID = x<\/td>\n<\/tr>\n
Message ID = x<\/td>\nPUBREL <\/span>

\n----------><\/code><\/td>\n		Actions:<\/strong> <\/p>\n
    \n
  • Make message available                       <\/li>\n<\/ul>\n<\/td>\n<\/tr>\n


\n<\/strong><\/td>\n		PUBCOMP <\/span>

\n<----------<\/code><\/td>\n		Message ID = x<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Server\u7aef\u91c7\u53d6\u7684\u65b9\u6848a\u548cb\uff0c\u90fd\u5305\u542b\u4e86\u4f55\u65f6\u6d88\u606f\u6709\u6548\uff0c\u4f55\u65f6\u5904\u7406\u6d88\u606f\u3002\u4e24\u4e2a\u65b9\u6848\u4e8c\u9009\u4e00\uff0cServer\u7aef\u81ea\u5df1\u51b3\u5b9a\u3002\u4f46\u65e0\u8bba\u6b7b\u91c7\u53d6\u54ea\u4e00\u79cd\u65b9\u5f0f\uff0c\u90fd\u662f\u5728QoS level 2\u534f\u8bae\u8303\u7574\u4e0b\uff0c\u4e0d\u53d7\u5f71\u54cd\u3002\u82e5\u4e00\u65b9\u6ca1\u6709\u63a5\u6536\u5230\u5bf9\u5e94\u7684\u786e\u8ba4\u6d88\u606f\uff0c\u4f1a\u4ece\u6700\u8fd1\u4e00\u6b21\u9700\u8981\u786e\u8ba4\u7684\u6d88\u606f\u91cd\u8bd5\uff0c\u4ee5\u4fbf\u6574\u4e2a\uff08QoS level 2\uff09\u6d41\u7a0b\u6253\u901a\u3002<\/p>\n

\u6d88\u606f\u987a\u5e8f<\/h3>\n

\u6d88\u606f\u987a\u5e8f\u4f1a\u53d7\u8bb8\u591a\u56e0\u7d20\u7684\u5f71\u54cd\uff0c\u4f46\u5bf9\u4e8e\u670d\u52a1\u5668\u7a0b\u5e8f\uff0c\u5fc5\u987b\u4fdd\u8bc1\u6d88\u606f\u4f20\u9012\u6d41\u7a0b\u7684\u6bcf\u4e2a\u9636\u6bb5\u8981\u548c\u5f00\u59cb\u7684\u987a\u5e8f\u4e00\u81f4\u3002\u4f8b\u5982\uff0c\u5728QoS level 2\u5b9a\u4e49\u7684\u6d88\u606f\u6d41\u4e2d\uff0cPUBREL\u6d41\u5fc5\u987b\u548cPUBLISH\u6d41\u5177\u6709\u76f8\u540c\u7684\u987a\u5e8f\u53d1\u9001\uff1a<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n
Client<\/th>\nMessage and direction<\/th>\nServer<\/th>\n<\/tr>\n<\/thead>\n
 <\/td>\nPUBLISH 1

\n----------><\/code>
\nPUBLISH 2
\n----------><\/code>
\nPUBLISH 3
\n----------><\/code>
\n<\/td>\n		 <\/td>\n<\/tr>\n
 <\/td>\nPUBREC 1

\n<----------<\/code>
\nPUBREC 2
\n<----------<\/code>
\n<\/td>\n		 <\/td>\n<\/tr>\n
 <\/td>\nPUBREL 1

\n----------><\/code>
\n<\/td>\n		 <\/td>\n<\/tr>\n
 <\/td>\nPUBREC 3

\n<----------<\/code>
\n<\/td>\n		 <\/td>\n<\/tr>\n
 <\/td>\nPUBREL 2

\n----------><\/code>
\n<\/td>\n		 <\/td>\n<\/tr>\n
 <\/td>\nPUBCOMP 1

\n<----------<\/code>
\n<\/td>\n		 <\/td>\n<\/tr>\n
 <\/td>\nPUBREL 3

\n----------><\/code>
\n<\/td>\n		 <\/td>\n<\/tr>\n
 <\/td>\nPUBCOMP 2

\n<----------<\/code>
\nPUBCOMP 3
\n<----------<\/code>
\n<\/td>\n		 <\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\u6d41\u52a8\u6d88\u606f(in-flight messages)\u6570\u91cf\u5141\u8bb8\u6709\u4e00\u4e2a\u53ef\u4fdd\u8bc1\u7684\u6548\u679c\uff1a<\/p>\n