Cart Start: Server
is an exchange for CartStart transactions, item ticketing and puchases..  The server acts like a chat room, connecting many web store fronts to a single user and many users to a single store front. The server is multi-threaded, where each thread connects to a store front.

Few Transaction Types The server handles just a few types of transactions. While it does not act as the manager of inventory, it does manage the messages that ensure the transactions that alter inventory are valid. Similarly, it acts as a gateway for payment.

Here are some of the server transactions:

1. User Login. A user session requires a login to the server. The user initiates a session with the server from the CartStart shopping cart. The server takes the login information, decodes it, and creates a user session object. After that, any CartStart page that relays information from a particular user browser sends a user identifier in each message. The user identifier becomes a key to the user session object.

2. Item Ticketing  When a user selects a product from a CartStart federated store, it is relayed to his desktop by a message passing through the CartStart server. Information about the item is carried in the message. In particular, an item ID, corresponding to a bar code goes with the message. The message, the one that carries the product identity, acts as a ticket for the item. Inventory count is supposed to drop because the ticket exists. As such, the ticket that identifies the item signifies the item being held on reserve. The ticket may expire after some time and relinquish the item, causing the inventory count to increase. Alternatively, the item may be purchased, and the ticket can be used in setting up shipment.

3. Session Relay. In order to make stores be a federation, a single user session needs to be carried from web server to web server. The CartStart server manages the login of a user, and retains, when possible, the client IP. If a user browser transition from one store site to another loses the user session information, the server can attempt to resolve the login, communicating with the store site via POST transactions with the store web server.

4. Shopping Cart Purchase   The shopping cart client relinquishes its tickets to the server at the time of purchase. The server parses out the purchased items in order to credit each store and arrange for shipping. A store may optionally have purchase transaction management at its site available to the server, or may let the CartStart server use backend payment system for crediting the store.