How can i redirect to another JSP page automatically after some event

Question

I am developing a Tic-Tac-Toe game which can be played between two players who are on two different machines.
When the first player comes to the Welcome page he will redirected to a Waiting Page when he clicks on the 'Start' button.
When the second player comes to the Welcome page he will be redirected directly to the Game page, on clicking the 'Start' button.
So how can i redirect the first player to the Game page after the second player is available for the game.
And if i want to manage multiple instances of my game how can i do that//
I am using JSP, javascript and MySQL for developing my project, and I am new to all these tools, but i would still like to carry on with all these only

Answer 1

This is a bit of a challenge because of the nature of the web. Generally the web is "pull only" meaning that the browser has to initiate any interactions - the server can't push data to the browser if it wasn't asked to.
The easiest way to solve this is using AJAX via JavaScript to periodically poll the server for any status changes. There are other ways (the Comet protocol is one) but they start to get a bit difficult and are still a bit new and not completely supported in a standards way. And to be honest they are still basically polling though in a more efficient way.
Are you using a JavaScript framework? Most of the JavaScript frameworks that I've used have built in support for polling in the background. You'd have to have the JSP/servlet side be able to handle these polling requests from the browser and, when another person joins the game, the server indicates that and sends that back to the browser.
As far as multiple instances I would have the server automatically pair up users as needed. So when the first player arrives he has to wait for another player. When the second player arrives a new game is created for those two players. Now a third player arrives and waits until a fourth player shows up. When player 4 joins another separate game is created. Presumably the conversation between the browser and the server will need to include a "game number" or other unique number so that the server can keep track of the games.