Need to close channels for a rebind?

[elias4444]

Just one thing after another with me... but as long as it's helping: 

I noticed that even if you call shutdown for the server and clients, it doesn't close any of the channels or ports. So, if you don't completely shut down the JVM before trying to restart a server instance, you get something like this:

Code:

Unable to bind to UDP port: 27995, trying: 27996.
java.net.BindException: Address already in use: bind
at sun.nio.ch.Net.bind(Native Method)
at sun.nio.ch.DatagramChannelImpl.bind(Unknown Source)
at sun.nio.ch.DatagramSocketAdaptor.bind(Unknown Source)
at com.captiveimagination.jgn.UDPMessageServer.init(UDPMessageServer.java:49)
at com.captiveimagination.jgn.UDPMessageServer.<init>(UDPMessageServer.java:33)
at jgnnetworkers.DGServer.<init>(DGServer.java:60)
at mainmenu.MainMenu.startServerSystem(MainMenu.java:827)
at mainmenu.MainMenu.begin(MainMenu.java:609)
at mpgame.MPGame.exittomainmenu(MPGame.java:2726)
at mpgame.MPGame.mousecheck(MPGame.java:2588)
at mpgame.MPGame.gameloop(MPGame.java:567)
at mpgame.MPGame.begin(MPGame.java:245)
at mainmenu.MainMenu.begin(MainMenu.java:619)
at mainmenu.MainMenu.splashscreen(MainMenu.java:442)
at mainmenu.MainMenu.main(MainMenu.java:1645)
Unable to bind to UDP port: 27996, trying: 27997.

I remember having this same problem with my code (as the TCP standard coupled with some funny Java ideas keeps the channel open). I just had to check if the channels were already initialized on server startup, and if they were, tell it to use the ones that were already there.

[darkfrog]

Well, the problem there is that you also have to shut down the UDPMessageServer and TCPMessageServer associated with each client and server.  I don't have the shutdown of the client and server kill the servers also because you might have something else that's using the same servers that you want to keep running.  If it would be beneficial I could have shutdown receive a boolean to say if it should also shutdown the servers?

darkfrog

[elias4444]

Actually, I haven't tried this yet, but I figured maybe I could just pause the server, clear it out, and keep using the same channels in order to fix this issue on my end. A little non-intuitive, but it might work.

[darkfrog]

Let me know what you come up with.  If you need some code changes to get it working more intuitively just let me know.

darkfrog

[elias4444]

Well, this was a tricky one, but I got it working (I think). Basically, you can't shutdown the server or the clients, you just have to leave them running, and then come up with a method to reinitialize your gamestate before going back to them. With the server, I put in a boolean variable that when set will pause the thread and then reinitialize all the counters and things once it's flipped back. You can't stop the thread though! Because if you do, you can't restart it, and you need to use the same instance of the server AND client. With the client, you can just call the "connect" method again to connect again.

[darkfrog]

Right, that's one of the rules of Java. Once a thread's run has exited it can never be restarted.

Was this entirely a code change on your side or did you have to make some changes to JGN?  If so, could you post those changes for me to take a look at?

darkfrog

[elias4444]

I was able to tweak it on my side (although I'm sure I've made some changes to your code, I don't think they were needed for the final solution). Java just simply doesn't close the channels until the JVM is completely exited.

[darkfrog]

Hmmm....that's probably an error on my part.  I'll try to do some testing with that when I get chance.  I'm sure there's a way to release the channel, I'm still pretty new to NIO though.

darkfrog