Hardware idea, ComLynx to LAN

[roland p]

I was thinking about the old days, when I was playing lynx games with 4 other friends. Awesome golf, Warbirds, Slimeworld, Checkered flag. It would be cool to experience that again! So I was thinking about a comlynx to internet adapter. It would involve the following:

 

- a real atari Lynx

- a comlynx to rs232 adapter

- a laptop/computer, with some magic piece of software, connected to the internet.

 

So the idea is to play the comlynx game on the lynx, let the laptop/computer capture the data, send the data to an other (or more?) computer, and let that other computer send that data to the lynx.

 

As I am totally convinced the above can be made. The main issue will be the speed of it. How much latency will occcur and how much latency will the lynx games accept. What do you think?

[else]

Other people have proposed the same thing in the past. Latency is the big problem. Since nobody knows how much the games will tolerate, you could end up putting in a big amount of time and effort -- only to reach the finish line and find out there's no way it will work. It's a chicken and egg problem.....

Edited November 14, 2008 by else

[famicommander]

I'd buy one, but I don't know how well it would work.

[Rybags]

I reckon latency would be a killer too.

 

An interesting idea though might be a system to allow a real Lynx to communicate with an emulated one via USB or RS232, or for 2 emulators on different machines to have a link via network.

[Shawn Jefferson]

I don't know that much about comlynx or how it works, but I know other emulators allow internet play by sending the joystick inputs across the net. If they can do it, I'm sure some smart brainiac here can get our Lynxes connected!

 

If latency is an issue, you will probably have to build some "keep-alive" mechanism, have the local software send fake signals from the remote lynxes, just to keep the connection alive. Will that work? What kinds of signals are sent, and what's the time frame they have to be sent in? If don't press any buttons on my lynx while lynxed up playing some game, is anything sent?

[Rybags]

I'm not sure how it works either, but I'd assume one takes the role of "Master" or "Server" and the other is a client.

 

What data actually gets sent? Hard to say... but since the exact same game runs on both machines, really all you need to know is joystick inputs, and the other machine can keep track.

 

But it mightn't be that simple - take for example some game where you might have 2 players independantly exploring a game world with pickups and enemies. The workload of keeping track of both players might be split such that each machine has to tell the other if e.g. a player kills an enemy or picks up an object, so that the other machine can then wipe it.

[roland p]

Other people have proposed the same thing in the past. Latency is the big problem. Since nobody knows how much the games will tolerate, you could end up putting in a big amount of time and effort -- only to reach the finish line and find out there's no way it will work. It's a chicken and egg problem.....

Then the first step will be finding out how much latency an atari lynx game will tolerate. I could program a microcontroller wich buffers the data and waits xx ms, and see what happens. The game will probably slow down until it reached a point where the package is considered lost, then the game will halt and try to reestablish the connection.

 

 

I don't know that much about comlynx or how it works, but I know other emulators allow internet play by sending the joystick inputs across the net. If they can do it, I'm sure some smart brainiac here can get our Lynxes connected!

 

But that is just like having 2 identical computers running the same game with the same joystick data?

With the lynx, there are several machines wich have to interact with eachother. So you would need to run 2 lynxes locally and 2 lynxes remote, local controls lynx 1 and remote controls lynx 2 and the joystick data will be replicated so both instances (local and remote) of lynx 1 and 2 are doing the same... phew.

[+karri]

There is actually a model of network traffic that is identical to ComLynx. It is called an UDP broadcast.

 

Instead of sending ComLynx serial packets the Lynx hardware could transmit UDP broadcasts on some dedicated port. And it could also listen on the same port.

 

It is not too difficult to build a small ComLynx - Ethernet cable that would just do a simple two way conversion like this.

 

For internet play you need a piece of software that would send the received broadcasts to all the participating computers on the internet. The broadcasts won't automatically leave the normal network.

 

As making software is much easier than making hardware I would suggest to make the ComLynx - Ethernet conversion on the same PC that takes care of sending things to the internet. The Lynx would then connect using a FTDI USB chip to some USB port.

 

Handy or Mednafen would then also need UDP broadcasts for their ComLynx traffic. This would allow you to mix emulators and real Lynxes in the same networked game.

 

--

Karri

[roland p]

There is actually a model of network traffic that is identical to ComLynx. It is called an UDP broadcast.

 

Instead of sending ComLynx serial packets the Lynx hardware could transmit UDP broadcasts on some dedicated port. And it could also listen on the same port.

 

It is not too difficult to build a small ComLynx - Ethernet cable that would just do a simple two way conversion like this.

 

For internet play you need a piece of software that would send the received broadcasts to all the participating computers on the internet. The broadcasts won't automatically leave the normal network.

 

As making software is much easier than making hardware I would suggest to make the ComLynx - Ethernet conversion on the same PC that takes care of sending things to the internet. The Lynx would then connect using a FTDI USB chip to some USB port.

 

Handy or Mednafen would then also need UDP broadcasts for their ComLynx traffic. This would allow you to mix emulators and real Lynxes in the same networked game.

 

--

Karri

 

UDP looks nice. I'm not really into protocols, but as far as I can see UDP has less overhead, and no verification. That's great since it will be only an extension of the physical layer. The lynx will do error detection etc.

 

Would you need portforwarding if you connect other computers through the internet? Or are there other methods?

Edited November 17, 2008 by roland p

[+karri]

There is actually a model of network traffic that is identical to ComLynx. It is called an UDP broadcast.

 

Instead of sending ComLynx serial packets the Lynx hardware could transmit UDP broadcasts on some dedicated port. And it could also listen on the same port.

 

It is not too difficult to build a small ComLynx - Ethernet cable that would just do a simple two way conversion like this.

 

For internet play you need a piece of software that would send the received broadcasts to all the participating computers on the internet. The broadcasts won't automatically leave the normal network.

 

As making software is much easier than making hardware I would suggest to make the ComLynx - Ethernet conversion on the same PC that takes care of sending things to the internet. The Lynx would then connect using a FTDI USB chip to some USB port.

 

Handy or Mednafen would then also need UDP broadcasts for their ComLynx traffic. This would allow you to mix emulators and real Lynxes in the same networked game.

 

--

Karri

 

UDP looks nice. I'm not really into protocols, but as far as I can see UDP has less overhead, and no verification. That's great since it will be only an extension of the physical layer. The lynx will do error detection etc.

 

Would you need portforwarding if you connect other computers through the internet? Or are there other methods?

 

Port forwarding is impossible. You need an user space proxy. I would use socat.

[semicolo]

Since few people are familiar with cygwin/unix, I'd suggest a simple UDP client/server scheme, port forwarding is probably easier to explain.

 

The clients connect to the server which sends evey data received back to everyone (or everyone but the sender depending what's needed)