{"id":462,"date":"2015-09-08T15:13:44","date_gmt":"2015-09-08T15:13:44","guid":{"rendered":"51d92be1c60d1db1d2e5e7a07da55b26"},"modified":"2015-09-08T15:13:44","modified_gmt":"2015-09-08T15:13:44","slug":"","status":"publish","type":"post","link":"https:\/\/www.xiaobo.li\/notes\/archives\/462","title":{"rendered":"\u4e09.MQTT\u534f\u8bae\u7b14\u8bb0\u4e4b\u53d1\u5e03\u6d41\u7a0b"},"content":{"rendered":"

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

\u8fd9\u6b21\u8981\u8bb2\u5230\u5ba2\u6237\u7aef\/\u670d\u52a1\u5668\u7684\u53d1\u5e03\u6d88\u606f\u884c\u4e3a\uff0c\u4e0ePUBLISH\u76f8\u5173\u7684\u6d88\u606f\u7c7b\u578b\uff0c\u4f1a\u5728\u8fd9\u91cc\u770b\u5230\u3002<\/p>\n

PUBLISH<\/h2>\n

\u5ba2\u6237\u7aef\u53d1\u5e03\u6d88\u606f\u7ecf\u7531\u670d\u52a1\u5668\u5206\u53d1\u5230\u6240\u6709\u5bf9\u5e94\u7684\u8ba2\u9605\u8005\u90a3\u91cc\u3002\u4e00\u4e2a\u8ba2\u9605\u8005\u53ef\u4ee5\u8ba2\u9605\u82e5\u5e72\u4e2a\u4e3b\u9898(Topic name)\uff0c\u4f46\u4e00\u4e2aPUBLISH\u6d88\u606f\u53ea\u80fd\u62e5\u6709\u4e00\u4e2a\u4e3b\u9898\u3002<\/p>\n

\u6d88\u606f\u67b6\u6784\u4e00\u89c8\uff1a<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
 <\/th>\nDescription<\/th>\n7<\/th>\n6<\/th>\n5<\/th>\n4<\/th>\n3<\/th>\n2<\/th>\n1<\/th>\n0<\/th>\n<\/tr>\n<\/thead>\n
Fixed header\/\u56fa\u5b9a\u5934\u90e8<\/strong><\/td>\n<\/tr>\n
byte 1<\/td>\n <\/td>\nMessage Type(3)<\/td>\nDUP flag<\/td>\nQoS level<\/td>\nRETAIN<\/td>\n<\/tr>\n
 <\/td>\n <\/td>\n0<\/td>\n0<\/td>\n1<\/td>\n1<\/td>\n0<\/td>\n0<\/td>\n1<\/td>\n0<\/td>\n<\/tr>\n
byte 2<\/td>\nRemaining Length<\/td>\n<\/tr>\n
Variable header<\/strong>\/\u53ef\u53d8\u5934\u90e8<\/td>\n<\/tr>\n
Topic name<\/td>\n<\/tr>\n
byte 1<\/td>\nLength MSB (0)<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n<\/tr>\n
byte 2<\/td>\nLength LSB (3)<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n1<\/td>\n1<\/td>\n<\/tr>\n
byte 3<\/td>\n'a' (0x61)<\/td>\n0<\/td>\n1<\/td>\n1<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n1<\/td>\n<\/tr>\n
byte 4<\/td>\n'\/' (0x2F)<\/td>\n0<\/td>\n0<\/td>\n1<\/td>\n0<\/td>\n1<\/td>\n1<\/td>\n1<\/td>\n1<\/td>\n<\/tr>\n
byte 5<\/td>\n'b' (0x62)<\/td>\n0<\/td>\n1<\/td>\n1<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n1<\/td>\n0<\/td>\n<\/tr>\n
Message Identifier<\/td>\n<\/tr>\n
byte 6<\/td>\nMessage ID MSB (0)<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n<\/tr>\n
byte 7<\/td>\nMessage ID LSB (10)<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n0<\/td>\n1<\/td>\n0<\/td>\n1<\/td>\n0<\/td>\n<\/tr>\n
Playload\/\u6d88\u606f\u4f53<\/strong><\/td>\n<\/tr>\n
BLOB\uff0c\u4e8c\u8fdb\u5236\u5bf9\u8c61\u5f62\u5f0f\u3002\u4e8c\u8fdb\u5236\u5177\u4f53\u5305\u542b\u7684\u5185\u5bb9\u548c\u683c\u5f0f\uff0c\u53ef\u6709\u5e94\u7528\u7a0b\u5e8f\u81ea\u8eab\u5b9a\u4e49\u3002\u82e5\u6d88\u606f\u4f53\u4e3a\u7a7a(0\u957f\u5ea6)\u4e5f\u662f\u53ef\u80fd\u7684\u3002<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\u56fa\u5b9a\u5934\u90e8<\/h3>\n

DUP flag\uff0c\u8bbe\u4e3a0\uff0c\u8868\u793a\u5f53\u524d\u4e3a\u7b2c\u4e00\u6b21\u53d1\u9001\u3002<\/p>\n

RETAIN flag\uff0c\u53ea\u6709\u5728PUBLISH\u6d88\u606f\u4e2d\u624d\u6709\u6548\u3002<\/p>\n