Curious as to how it works...??

[azz1844]

Hi there!

Sorry if this has been answered somewhere before...
But I was curious as to how the online play on ZSNES is actually achieved (I have been speculating with a friend).

Do you actually need to change the coding of the original game ROM, or do you simply get the software to "trick" the ROM into thinking another computer somewhere else on a network is "Controller Port 2"?

(I have been guessing the latter option up until now, but I have a very limited knowledge of how software programming works!)

Thanks for any info you can give me!!

[Deathlike2]

This is very much the latter.

[creaothceann]

When the game requests the controller status, ZSNES supplies the keyboard status of the PC it's running on (local gameplay) or from a connected PC (netplay).

[AntoineWG]

More accurately, ZSNES is constantly sending controller information and other data back and forth between the computers, giving controller input timings to both ROMs simultaneously, all while trying (with varying degrees of success) to keep the games in sync.

[azz1844]

Thanks very much!!!

I guessed something along those lines, but like I said, limited background knowledge!

Another of the reasons I was wondering this, is because in a lot of Nintendo Wii forums people have been speculating about adding online gaming to Virtual Console games. Some people have been saying its very unlikely because it requires altering the original ROMs, which would pose the added difficultly of getting third parties to do this.
But I use ZSNES as a comparison and suggested that they could just "trick" the ROMs into thinking another Wii was another controller port, just as Netplay does.

Obviously ZSNES is pretty unofficial as far as the games on it are concerned, but what do people here think about online Virtual Console games using that method (via an official software download from Nintendo, of course)? Sound viable?

[creaothceann]

That should also be possible.

SNES games get the controller status by repeatedly reading two memory addresses (which happen to be mapped to the controller ports). Emulators check all memory "reads" and "writes" for special addresses, and act accordingly (e.g. returning the keyboard status upon a "read"). When they're connected via Netplay they can just use the other PC's keyboard status.