Deploying your Web UI game

When you build a TADS game with the Web UI library, there are two ways for players to run the game: client/server, or stand-alone.

Client/server mode means that the game runs on an Internet server, and the player accesses the game through an ordinary Web browser. This setup is ideal for players who don't want to install any software, since there's no need to download your game or install TADS; the player simply clicks a hyperlink and the game loads in the browser.

Stand-alone mode works just like traditional TADS games: the player installs the TADS interpreter, downloads your game, and runs the game with the interpreter. This isn't anything separate you have to program; it's handled automatically by the interpreter. When a player launches your Web UI game locally, the interpreter automatically opens a browser window and sets up a virtual network connection. As far as your game is concerned, it's running as a network server, just as it would in true client/server mode; but from the player's perspective, everything looks and acts like a traditional downloaded TADS game.

There are trade-offs to each mode. Client/server mode requires a network connection throughout the game session, since the game logic runs on the server; it also tends to be a bit slower, since each command input requires information to be sent back and forth across the Internet. Local mode doesn't require a network connection during play, and it's not affected by network delays; but it's more work for players to set up, since they have to download both your game and the TADS interpreter.

Deploying for client/server play

There are two options for client/server deployment.

First, you can use the public TADS server network. This is a collection of servers set up by volunteers to run any TADS Web UI games. Deploying with the public server network is simple: you upload your .t3 file to the IF Archive, and create an IFDB page for it. Add a link from the IFDB page to the IF Archive upload, marking it as a TADS 3 Web UI game. The IFDB page will automatically display a "play online" button; players click the button, and IFDB will automatically find an available public server and launch the game.

Second, you can set up your own server specifically for your game. This gives you full control over the server, but it's much more complicated - it requires that you have your own Web server, and it involves some software installation and configuration. The details are covered here.

Publishing for stand-alone play

To make your game available to players for stand-alone play, you simply publish it the same way you publish a traditional TADS game. This usually means uploading your .t3 file to a site such as the IF Archive, or, if you have a personal Web site, posting it on your site.

Saving games in the "cloud"

TADS games sometimes access external data files. The most common use for external files is to save and restore game positions. Most games also allow for transcript files, and some games use files for special purposes, such as saving information that persists across multiple sessions.

The traditional place to store all of these files was simply on the local computer's hard disk. For client/server play, though, this isn't suitable. We don't want to store files on the client computer (the player's machine, where the Web browser is running), because this would somewhat defeat one of the nicer features of Web play, which is that you can play from any computer. If we stored saved games on the client machine, the player couldn't later resume playing on another machine. And even if we wanted to store them on the client, we really can't: browsers don't allow servers to store arbitrary data on a client computer, largely for security reasons, since this would make clients too vulnerable to viruses and other malicious software.

At first glance, then, it might seem better to store saved games on the server. But this isn't ideal either. First, if you're using the public TADS server network, each session might run on a different server - so if we saved files on the server, the user wouldn't be able to find them again if they resumed play and happened to be assigned to a different server. Second, even if the server were always the same, we have the complication that the same server will be accessed by multiple users. If we stored saved games on the server, there'd be a jumble of files from different players, making it difficult for each player to find their own files. The obvious solution would be to ask users to identify themselves, by logging in with a username and password, but this is probably asking too much - people are already burdened with remembering so many login details as it is that they'd probably be quite cross with us if we asked them to create yet another password for each new game they want to play.

What we really want to do is store files in the "cloud" - somewhere on the Internet that's accessible from anywhere, and where you can always find something you saved earlier, even if you've switched to another browser device.

IFDB storage server

The solution we've come up with is to set up a separate network server just for file storage. This "storage server" is separate from the game servers, and most importantly, there's just one - we always know where to find a file, since there's only one place to look. (You might wonder why we need many game servers but can make do with one storage server. The difference is resource usage. File storage requires very little computing power, whereas game execution requires a fairly hefty amount of memory and CPU time. The only practical way to allow for a large number of concurrent players is to spread the users across multiple execution servers. In contrast, a single file server should be sufficient for a large number of concurrent players.)

There's still the problem of how to tell each player's files apart from those of other players. As we said earlier, the only good approach is to require users to log in. We felt this was too much to ask on a game-by-game basis; but with a single, centralized storage server, it becomes a much more reasonable proposition. To make it even more palatable to users, the TADS storage server is set up as part of IFDB, so players simply use their existing IFDB credentials. Many people interested in IF already have IFDB accounts; for players new to IFDB, it's fairly painless to create an account, since it's free and doesn't require divulging any personal information.

Connecting to the storage server

To use the IFDB storage server, the user must launch the game through IFDB. The IFDB page for a TADS game with a Web UI will offer a "Play Online" link; the user can launch the game by going to the game's IFDB page and clicking this link. Alternatively, you can set up a direct link from your own Web site to the IFDB launch page, following this template:

<a href="">Play Online</a>

In the HREF string above, replace TUID with your game's IFDB TUID - you can find this information in the "Details" section of the game's IFDB page. (If you haven't already created an IFDB page for the game, you'll need to create one before you can use the storage server system.) Replace FILE with the name of your .t3 file on the IF Archive - you only need the filename portion, since the server will assume it's on the IF Archive in the games/tads section. For example:

<a href="">Play Online</a>

Upon reaching the "Play Online" page, if the user isn't already logged in, IFDB displays a login screen. The user can enter her credentials, or can opt to play without logging in. In the latter case, the storage server won't be used, since all files on the storage server are per-user.

When the user launches the game using this procedure, the storage server creates a "session" that's specific to the game and the user, and generates an identifying key for the session. The key is essentially a temporary password that applies only to the particular game and user, and only for the duration of the current session. IFDB passes the key to the TADS interpreter. The interpreter then uses the key to perform file operations on the storage server.

Saving and restoring games

The saveGame() and restoreGame() functions automatically use the storage server session information that IFDB passes to the interpreter upon launch. This is transparent to your game; you don't have to do anything different.

Log files

The setLogFile(), setScriptFile(), and logConsoleCreate() automatically use the storage server session information, transparently to your game.

File objects

The File intrinsic class automatically uses the storage server session information to manage files. When you open a file, the File class communicates with the storage server to read or write the file data.

inputFile dialog

You shouldn't use the inputFile() function directly in a Web UI game, since this function isn't aware of the storage server. Instead, always use the Adv3 equivalent, inputManager.getInputFile(). When a storage server is in use, this method instructs the browser to display a dialog managed by the storage server itself. This dialog allows the user to select files on the server, and communicates the selection information back to your game program as though the ordinary inputFile() function had been used.

Running without a storage server

If the user opts not to log in to IFDB, they can still play the game, but they won't be able to take advantage of "cloud" storage. Instead, the Web UI library will fall back on local storage on the user's PC.

When the user saves a game or creates a log file, the game will initially store the data in a temporary file on the server. It will then send the file to the user's PC as a download. Most browsers will respond by displaying a file selector dialog so that the user can specify where to store the downloaded data. This satisfies the security restrictions imposed by the browsers, to guard against sites attempting to download files without the user's knowledge. It also happens to be almost identical to the workflow for saving games in the traditional interpreter, so users should find the process readily intuitive.

When the user enters a RESTORE command to load a game, the server displays dynamic HTML that prompts the user to select a file for upload. Most browsers will display a button that the user can click to select a file via a file selector dialog; some will open a file selector dialog directly. In any case, assuming the user selects a file through the dialog, the browser uploads the file to the server, and the server captures the upload as a temporary file. It then performs the RESTORE operation using the temporary file. As with SAVE, the process is very similar to the equivalent workflow in the traditional interpreter.

Using File objects without a storage server works like SAVE and RESTORE. When you open a file for reading, the browser interactively asks the user to select a file for upload. When you close a writable file, the browser prompts the user to save a downloaded file. This behavior is different from the traditional interpreter, which performs File object read/write operations without involving the user. The interactive prompting is required due to browser security restrictions; browsers don't allow remote Web servers to read or write client-side files silently, since this would allow malicious sites to read your private files and/or download potentially dangerous files without your knowledge or consent. Because of this cumbersome user interaction procedure, it's probably best to avoid using File objects in Web UI games as much as possible. If you really need to use File objects, you should at least warn the player that logging in to IFDB is strongly recommended; you can determine if a storage server session is in use by checking webSession.storageSID. Alternatively, if you're using File objects for temporary storage only, you can use TemporaryFile objects to create server-side temporary files without any user interaction.