Is somewhere a project which i can take a look???
It isn't any different from reading from Serial or reading from EthernetClient. Look at any of the bazillions of examples around. Or just try something.
Start with the simplest task. Define an array to put data in. Define an index into that array. Increment the index after storing a character. Add a NULL to the array, without incrementing the index. Then, all that is left to do is to reset the index value at the appropriate time, and stuff a NULL in the array at the new index location.