Update README.md

Author: TeemuKultala

README.md

@@ -49,7 +49,7 @@ See the file `mbed_app.json` in the root directory of your application. This fil
 
 ### Selecting socket type (TCP or UDP)
 
-You can choose which socket type the application should use. For example:
+You can choose which socket type the application should use. Please note that TCP is more reliable tranmission protocol. For example:
 
 ```json