Programming Flash Communication Server

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Chapter 3: Managing Connections

All the preceding examples are available in a Zip archive file from http://flash-

communications.net. The archive includes the file com/oreilly/pfcs/FCSConnector.as.

That file must be extracted from the archive with its path intact (most unZip pro-

grams have a Maintain Folders option for this purpose) and placed in a directory in

the classpath of Flash MX 2004. See Chapter 9 of Essential ActionScript 2.0

(O’Reilly) for more information on packages and the classpath.

Communication Components Without

SimpleConnect

Chapter 2 showed how applications can be created using Macromedia’s communica-

tion components. Macromedia supplies the SimpleConnect component to manage a

network connection and connect all the other components to it. SimpleConnect

allows users to log in using any name when they connect—even the same name

someone else is using. If you need to develop an application that manages user iden-

tities differently but want to use Macromedia’s communication components, there

are two options. One is to write your own connection component. Chapters 13

through 15 describe how to build custom components. The other option is not to

use a connection component at all, as illustrated in the final example in Chapter 2.

The following example uses a little server-side scripting, a NetConnection subclass,

and the communication components to demonstrate creating a basic chat room

application with separate login and chat screens. The application enforces unique

usernames, doesn’t allow name changes while connected, and does not permit lurk-

ing. It is not designed to provide a lobby and multiple chat rooms. These and other

enhancements are added in later chapters.

Creating the Application on the Server

To use the communication components without SimpleConnect, an application’s

main.asc file must load the component framework and store a username for every cli-

ent that connects within the framework. A minimal main.asc file is shown in

Example 3-12.

button.label = "Connect";

nc.close( );

}

}

function writeln (msg) {

msgTextArea.text += msg + "\n";

msgTextArea.vPosition = msgTextArea.maxVPosition;

msgTextArea.redraw( );// Fixes scrolling bug in TextArea as of Flash 7.2.

}

Example 3-11. Importing and using the FCSConnector class in the main timeline of a movie

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Communication Components Without SimpleConnect

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Example 3-12 allows anyone to connect with any username. To reject connections in

which the username is blank or already in use requires a little more work.

Example 3-13 shows a listing of another main.asc file. The script uses an object

named

users to keep track of the userName associated with each Flash movie. (An

object such as

users, in which the item name is used to access array elements, is

known as an associative array, hash table, or simply hash.) The trim( ) function is

used to preprocess each

userName before checking whether it is null, an empty string,

or already in the

users object.

Example 3-12. Minimal main.asc file when SimpleConnect is not used

load("components.asc");

application.onConnect = function (client, userName) {

gFrameworkFC.getClientGlobals(client).username = userName;

application.acceptConnection(client);

};

Example 3-13. The main.asc file for the netConnectChat application

load("components.asc");

// Trim any whitespace from before or after the userName.

// SSAS supports regular expressions, but client-side ActionScript does not.

function trim (str) {

if (typeof str != "string") return ""; // Make sure str is a string.

str = str.replace(/^\s*/, ""); // Trim leading spaces.

str = str.replace(/\s*$/, ""); // Trim trailing spaces.

str = str.replace(/\n/g, ""); // Remove new lines.

str = str.replace(/\r/g, ""); // Remove carriage returns.

str = str.replace(/\t/g, ""); // Remove tabs.

return str;

}

// Hash of client objects using the userName as a property name.

users = {};

// The onConnect( ) method rejects connection attempts

// where userName is invalid text or is already in use.

application.onConnect = function (client, userName) {

userName = trim(userName); // Remove leading and trailing whitespace.

if (userName.length == 0) { // If it is empty, reject it.

application.rejectConnection(client, {msg: "Empty username."});

return;

}

if (users[userName]) { // If it is in use already, reject it.

application.rejectConnection(client,

{msg: 'The username "' + userName + '" is already in use.'});

return;

}

// Store a reference to the client in the users hash.

users[userName] = client;

gFrameworkFC.getClientGlobals(client).username = userName;