You can't have a null character (\x00 or \0) in a string. You have to use .write() with "char *, int" arguments where the 'int' is the number of characters. I think this will work:
client.write("[P]\x00\x02\x06\x0d\x0a", 8);
I don't know where they got 0x0E for LF (Linefeed). It's 0x0A. 0x0E is SO (Shift Out)