Exercises • 181

have to change the index 0 in the statement arduinoPort = new Serial(this, Seri-

al.list()[0], BAUD_RATE); accordingly.

•You forgot to plug the Ethernet cable into the Ethernet shield.

•Your network router has a MAC whitelist that allows only certain MAC addresses to access the network. Make sure that the MAC address you use in your sketches is whitelisted. Check your router’s documentation.

•You have used the same MAC address twice on your network.

•You’ve used an IP address that isn’t allowed in your network or that is used already by another device. Double-check your IP address.

•You’ve used the wrong credentials for accessing a service such as Twitter. Make sure you use the right OAuth tokens.

•Twitter doesn’t allow duplicate Tweets. So, whenever your application fails to Tweet a message, make sure you haven’t Tweeted it recently.

•Networks have become very reliable over the last couple of decades, but sometimes they are still fragile. So, it might well be that connections fail or that you run into timeouts. Try increasing the delays in your sketches.

Exercises

•Search the Web for other Ethernet shield projects and build at least one of them. A very ambitious project tries to implement a complete web browser on the Arduino, for example.13

•Register an account at Xively, Temboo, or any other IoT service. Work through their tutorials and create at least one Arduino application.

•Try at least one additional networking technology, such as Bluetooth, WiFi, or XBee, with your Arduino.

13. http://hackaday.io/project/3116-pip-arduino-web-browser

report erratum • discuss