As long as you are in the ethernet library reference, the following pages need an addition.
The pages are missing one of the most useful functions if you plan on sending any NULL (zero) bytes.
client.write(dataString,count);
server.write(dataString,count);
Parameters
dataString: the array to write (byte or char array pointer)
count: the number of bytes of the dataString array to write (int)
edit: Corrected dataString parameter to "byte or char array pointer".
I've edited the Client and Server write() pages, thanks for the suggestion and for noticing.
I preferred to keep the explanation close to the one given to Serial write() documentation.
Hope you like it.