Available design solutions for a server-client protocol in a web environment

Let's say I have a server running as a service, I have a client that connects to the server exchanging information.

This will work nicely on a "keep-a-live" application (a desktop applicati开发者_Go百科on, another service etc.), but what are my option in a web environment? Create the client on each web call and connect to the server retrieving information?

Is there any other choice if it is a must for the client to be a "keep-a-live" client even on a web application?

Eg. put the client inside a service locally and somehow retrieve information from the web application to the "client in server".

Why I need the client to be a "keep alive" type of client is because it will serve as a local cache being updated form the server etc. And if I have to recreate the client on every web call the cache will not be of much use.

Anyone got any solutions?

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Yes. I would create the client as a service. I'm curious: what will consume the cache maintained inside this client. I guess I'm asking what is the client of the client?