The article just said how to send a string with a package, but how do I request methods to be ran? :-)
When the data is received on client or server, you should parse what is coming in the string. Imagine, you send from client to server following string: "upd_pos:1:10:15". On server you got some kind of selector(at list I use to call the method which detects what request was received from client), which takes the first part of the string and analyze it. Selector detects that the first string is "upd_pos", so it knows what is the method needed to handle the data, for example method updatePosition. You pass the string, or the unparsed part of the string to the method and the method updatePosition continues parsing.
There should be defined protocol, either made by yourself or already existing one, protocol is need for server to know what each string means. Though the string I gave you is just an example, in case of communication probably I would use JSON or in worth case XML(in my own practice using XML for RT games generates much more traffic then JSON).