some advice:

1: learn how to use a network to establish a connection between two applications.[It is recommended to use TCP]

2:how to transfer a message(safety) between server and client;[ yes, u can use Google Protocol buffers , its a good choose]

3:now you can deal with your agreement, such as pick up item or use a skill;

4:them, u can do some to save data and load data when player online.

there have a opensource solution written by me,it contains those I said above.https://github.com/ketoo/NoahGameFrame