Reads UDP data from the specified buffer. If no arguments are given, it will return the next character in the buffer.
This function can only be successfully called after
// SYNTAX count = Udp.read(); count = Udp.read(packetBuffer, MaxSize);
packetBuffer: buffer to hold incoming packets (char)
MaxSize: maximum size of the buffer (int)
int: returns the character in the buffer or -1 if no character is available