Displaying a percentage from my sensor

Solved
4

That shouldnt be happening.
You do seem to be missing some code related to the Ethernet shield, where you define the CS pin (GPIO4) as an output pin then set it HIGH to disable the SD card.
The SD card and the Ethernet port share the same interface, so this is necessary to switch the SD card off so that the Ethernet port can be used.
If you take a look at the sketchbuilder you’ll see code like:

#define W5100_CS  10
#define SDCARD_CS 4

[in void loop......]
  pinMode(SDCARD_CS, OUTPUT);
  digitalWrite(SDCARD_CS, HIGH); // Deselect the SD card

Maybe this is the issue?

Having said that, I tried to persevere with the Arduino Ethernet shield for a long time, but couldn’t get around random lockups that would require the board to be reset to overcome the issue.
Have a read of this…

Pete.