Merge pull request practical-tutorials#187 from codepr/master

Added Sol - An MQTT broker from scratch tutorial

Author: tuvtran

README.md

@@ -106,6 +106,15 @@ To get started, simply fork this repo. Please refer to [CONTRIBUTING.md](CONTRIB
   - [Part 4 - libuv](https://eli.thegreenplace.net/2017/concurrent-servers-part-4-libuv/)
   - [Part 5 - Redis case study](https://eli.thegreenplace.net/2017/concurrent-servers-part-5-redis-case-study/)
   - [Part 6 - Callbacks, Promises and async/await](https://eli.thegreenplace.net/2018/concurrent-servers-part-6-callbacks-promises-and-asyncawait/)
+ 
+- MQTT Broker from scratch
+  - [Part 1 - The protocol](https://codepr.github.io/posts/sol-mqtt-broker)
+  - [Part 2 - Networking](https://codepr.github.io/posts/sol-mqtt-broker-p2)
+  - [Part 3 - Server](https://codepr.github.io/posts/sol-mqtt-broker-p3)
+  - [Part 4 - Data structures](https://codepr.github.io/posts/sol-mqtt-broker-p4)
+  - [Part 5 - Topic abstraction](https://codepr.github.io/posts/sol-mqtt-broker-p5)
+  - [Part 6 - Handlers](https://codepr.github.io/posts/sol-mqtt-broker-p6)
+  - [Bonus - Multithreading](https://codepr.github.io/posts/sol-mqtt-broker-bonus)
 
 ### OpenGL: