I have the arduino and ethernet shield working as a server and responding to a clients request but what I want to do is to respond to that client at regular intervals without having the client make more than one request. For instance, posting voltage levels of some output pins every 10 seconds for a given amount of time. Can this be done?
See also...
Can this be done?
Keep in mind that a client/server relationship is generally stateless. The server knows nothing about the client. When the client makes a request, the server generates a response as though it had never heard of that particular client before.
Can you imagine google having remember what every computer in the world last searched for?
If there is to be a state maintained, it is generally the client's responsibility to maintain the state. Therefore, you should be modifying the client to make periodic requests, not modifying the server to maintain a link to the client, so it can send periodic data.
OK. All of this is a help. I guess I was looking at it from the wrong direction. I will concentrate my efforts to work from the client side instead of the arduino server side. Thanks for all the help.
Guessing: You have an Arduino, with sensors.
It is serving a web page, with data from the sensors.
You want a big computer to "write down" a history of readings seen, sampling the Arduino-served data every so often... be it every 10 seconds or once an hour... academic, within reason.
If that's the need, then yes! You are there! Make the client, the big computer, do the work of knowing when to call the Arduino for the latest data.