add readme step

board/Linux_Posix/mqtt_demo/readme.md

@@ -6,6 +6,38 @@ make sure your develop environment.
 + `gcc` `gdb` `make` is installed
 
 ## step2
+configure your server and add a transmit rule
+
+reference [tencent cloud IoT guide?](../../../doc/8.TencentOS-tiny对接腾讯云IoTHub开发指南.md)
+
+additional thing, add a rule for send a message to the demo
+1. select filter topic is the ${demo device}/event and 
+SELECT * FROM ${demo device}/event
+2. select action type is Republish and topic is the ${demo device}/control
+
+the page like this
+_____________________________________________
+|规则引擎
+|--------------------------------------------
+|基本信息
+|规则名称  loop
+|规则描述  未填写
+|--------------------------------------------
+|筛选数据
+|字段  *
+|Topic  ${demo device}/event
+|条件
+|当前SQL语句是：
+|SELECT * ${demo device}/event
+|--------------------------------------------
+|行为操作
+|行为类型  数据转发到另一个Topic ( Republish )
+|Topic ${demo device}/control
+|  ...
+_____________________________________________
+
+
+## step3
 generate `mqtt_config.h` file to replace `./inc/mqtt_config.h`
 
 cd `tiny/tools/` directory, run python script
@@ -16,7 +48,7 @@ python3 mqtt_config_gen.py
 then input your server configuration, generate `mqtt_config.h` file
 copy to `./inc/` replace old file
 
-## step3
+## step4
 make `build` directory and compile in `build`
 
 ```bash
@@ -25,7 +57,7 @@ cmake ..
 make
 ```
 
-## step4
+## step5
 run program !!
 
 ```bash