Sanity Check - Is a Multiplayer Game Server in Java using TCP (ServerSocket) viable?

Question

Hey Guys,

Please stop me before I make a big mistake :) - I'm trying to write a simple multi-player quiz game for Android phones to get some experience writing server code.

I have never written server code before.

I have experience in Java and using Sockets seems like the easiest option for me. A browser game would mean platform independence but I don't know how to get around the lack of push using Http from the Server to the Browser.

This is how the game would play out, it should give some idea of what I require;

A user starts the App and it connects using a Socket to my server. The server waits for 4 players, groups them into a game and then broadcasts the first question for the quiz. After all the players have submitted their answers (Or 5 seconds has elapsed) the Server distributes the correct answer with the next question.

That's the basics, you can probably fill in the finer details, it's just a toy project really.

MY QUESTION IS;

What are the pitfalls of using a simple JAR on the server to handle client requests? The server code registers a ServerSocket when it is first run and creates a thread pool for dealing with incoming client connections. Is there an option that is inherently better for connection to multiple clients in real time with two way communication?

A simple example is in the SUN tutorials at the bottom you can see the source for a multithreaded server, except that I have a pool of threads initially to reduce overhead, my server is largely the same.

How many clients do you expect this system to be able to handle? If we have a new thread for each client I can see that being a limit, also the number of free Sockets for concurrent players. Threads seem to top out at around 6500 with the number of sockets available nearly ten times that.

To be honest If my game could handle 20 concurrent players that would be fine but I'm trying to learn if this approach is inherently stupid. Any articles on setting up a simple chess server or something would be amazing, I just can't find any.

Thanks in advance oh knowledgeable ones,

Gav

Answer 1

It should be able to do it without an issue as long as you code it properly.

Project Darkstar

Answer 2

You can get around the "push from server to client over HTTP" problem by using the Long Poll method.

However, using TCP sockets for this will be fine too. Plenty of games have been written this way.

Answer 3

You can handle 20 concurrent players fine with a Java server. The biggest thing to make sure you do is avoid any kind of blocking UI like it was the devil itself.

As a bonus, if you stick with non-blocking I/O you can probably do the whole thing single-threaded.

Scaling much past 100 users or so may need to get into multiple processes/servers, depending on how much load each user places on your client.