Example of using unity socket server, library and docs can be found at https://github.com/slessans/unity-socket-server/
Open the only scene and run the project. In the console you will see (along with probably a lot of other debug output) the host and port number on which to connect. Connect to this and the server will start reading.
Send position values (3-tuples of floats, separated by "&") and the cube in the scene will update it's position accordingly.
An example sequence of tokens could be "0.0,0.0,0.0&1.0,1.0,1.0&". Remember if sending only one token, the separator must still be at the end or it won't be read.