HTML5 Canvas, 2nd Edition

The Basic Architecture of a Socket-Server Application

Now that you have ElectroServer ready to go and you have the JavaScript API, it is time to learn a bit about how socket-server-based multiplayer/multiuser applications are designed. Using a socket server means you are creating an application that relies on a client for input from a user, as well as relying on a server to distribute that input to other users who are connected to the first user.

A good example of this is a chat application. Most chat applications require a user to enter a room (a logical space in which people are “chatting”—that is, exchanging messages), where that user can see the messages of other people in the same virtual space. In that room, the client is “connected” to those other users. However, it is usually not a direct connection (such as peer-to-peer), but instead, it is a connection through a port to a socket server.

The socket server acts as the traffic cop for the chat messages. It listens on a port (in our case, 8989) for messages coming in from the clients. Those messages need to be formatted in a way that the server can understand so that it can process them. The JavaScript API we will use performs this formatting for our client applications.

When the socket server receives a message from the client, it routes the various text messages sent by each client back out to the other clients in the room. However, it can also do much more by using server-side processing, such as holding the list of current ...