Why?

• The default (microsoft) client is horrible, so you have to use a different client like pidgin
• My account was created way back when you had to use a hotmail account to do it, and having a hotmail account is actually quite embarrassing.
• It’s a closed format, so when Microsoft changes something, all the clients that does not sucks breaks, and closed formats are ideologically incompatible with the concept of a free and open Internet.
• I hate Microsoft, and by the laws of transitivity everything they make.
• By using the Live Messenger protocol, you can only talk to other users of MSN live messenger. Using Live Messenger is like having a Hotmail account that you can only use to send/receive emails from other Hotmail users. Nobody would use such a limited and retarded mail service, but for some reason people are OK with using a IM service that works like this.

The alternative

The only viable alternative was to go with XMPP, which is an open and standardized protocol which anyone can use. XMPP is pretty much like email, anyone can set up a server and anyone who has an XMPP account can contact anyone else who has a XMPP account no matter which server they use.

The choice of server was between jabber.org or Google (there are thousands of other XMPP servers you can use, but these are the largest ones), but since jabber.org’s registration page was down while they were moving their servers, and I already have a Google chat account (which uses XMPP), the choice was pretty simple

This is how I proceeded in locating the memory leak, this method could easily be adapted to other programs.

Trekwar is turn based, so each turn the client downloads a Galaxy object from the server. There are many references to this objects inside action listeners, threads, etc..

WeakReference
To make a long story short, a weak reference is like a normal reference, except it will not prevent the object it points to from being garbage collected.

This means that is you  have a normal and a weak reference to object A, the weak reference will be null if you remove the “hard” reference.

1) In the client main executable (the class that holds the method that updates the map from the server). Import, declare and make a list of weak references

Code block

import java.lang.ref.WeakReference;
private ArrayList<WeakReference<Galaxy>> weakRefs;
 
weakRefs = new ArrayList<WeakReference<Galaxy>>();

2) Find the place in your program where a new object is being added, in my place this is the localGalaxy object. Create a weak reference to this object, and list all your weak references.

Code block

localGalaxy = (Galaxy) objStream.readObject();
weakRefs.add(new WeakReference(localGalaxy));
for(int i = 0; i < weakRefs.size(); i++) {
System.out.print("ref # " + i + " = ");
try {
Galaxy testG = (Galaxy)weakRefs.get(i).get();
System.out.println(testG + ", tick = " + testG.currentTick);
}
catch(NullPointerException npe) {
System.out.println("null");
}
}

And you’re done!

Now when you run the program, you should see something like this each time the method is called

Code block

ref # 0 = org.aakretech.trekwar2.common.Galaxy@11ed166, tick = 37
ref # 1 = org.aakretech.trekwar2.common.Galaxy@9801f4, tick = 37
ref # 2 = org.aakretech.trekwar2.common.Galaxy@1c5d81c, tick = 38
ref # 3 = org.aakretech.trekwar2.common.Galaxy@101f8f4, tick = 39
ref # 4 = org.aakretech.trekwar2.common.Galaxy@1ed1e7e, tick = 40
ref # 5 = org.aakretech.trekwar2.common.Galaxy@e0a7ea, tick = 41

Unless you want to wait until your GC decides it’s time to go, use a tool like VisualVM to force the Garbage Collector to run.

After the GC has run, the output should look like this:

Code block

ref # 0 = null
ref # 1 = null
ref # 2 = null
ref # 3 = null
ref # 4 = null
ref # 5 = null
ref # 6 = org.aakretech.trekwar2.common.Galaxy@2b3c91, tick = 42

Now, this means that the object IS being garbage collected, and there is no memory leak.. If you run this and the object you are monitoring (in this example the localGalaxy object) is not GC’ed because of stray references, you can tell because none of the references will point to null.

Now I’ve managed to get most of what I broke, working again (Research and Starsystem Control), and I’ve added a glasspane that shows up and prevents the clicking of buttons (and thus creating a weird state of the client) while each tick is being processed by the server.

Currently the test galaxy is 100×100 tiles and takes about 0.5 seconds to load to client

Unlike the previous version of the game, it is now possible to have many windows active on top of the actual game map.
The system box (far left of the screen) has been changed to display more information, and next up is a complete redesign of the fleet box.

But before making the new fleet box and fleet management system, I’ll have to do some major rewrite of the internal ship system and logic, to support user created ship classes.

I’m looking forward to 8-10 hours of pure java and logic.. There is only so much Swing a man can take

The client however will crash after about 10 ticks if the galaxy is really big. Have stared at the code for hours, with no result. I’m going to have to start some methodical and very tedious debugging to get this thing fixed

Well, I still have to crawl trough memory alpha to get images for all the 65 technologies in the game. but all the code and the GUI is complete:

Next I will make the client download and display the new map / research view each time the server starts a new turn.

After that I will be working on the order system, and doing either the build order system (creating new buildings on planets), or the fleet order system (moving starships, giving attack/colonize orders, etc..). Still LOTS to do, and it feels good to have Research out of the way.