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Gui freezes only when using multiple frames and 'while' socket is listening

Karel Tevarnier

Joined: Apr 21, 2006
Posts: 2

I've been searching for hours to solve this problem. Tested a lot of things but haven't figured it out. I hope someone here can help me.

I'm writing a Server-Client Chat application. User must be able to select what to run: Client, Server, or both. So I made a 'Launcher' Class with a JFrame.

Then I have 2 classes Clientwindow and Serverwindow wich extend an abstract class chatwindow. With that abstract class extending a JFrame.

In the Serverwindow Class there's a listening while loop:


wich starts a new thread for the client.

So far so good, but now I have a weird combination of facts...

- If I only start the Serverwindow without the Launcher: No problem
- If I try to start Serverwindow and Clientwindow at the same time: Only Serverwindow appears
- If I start Serverwindow with the Launcher (JFrame): Both frames freeze and program hangs
- If I start Serverwindow without the while loop: No problem

thanks for the help
Roseanne Zhang
Ranch Hand

Joined: Nov 14, 2000
Posts: 1953
It is very hard to know your problems without the actual code or the runnable program...
Ernest Friedman-Hill
author and iconoclast

Joined: Jul 08, 2003
Posts: 24189

Hi Karel,

Welcome to JavaRanch!

Roseanne is right, of course, but I can make a good guess: you put the "accept()" loop above right into an event handler of your GUI. Note that all events get handled on the same thread; by putting an infinite loop in an event handler, you prevent the GUI from ever receiving another event, and so the program appears to "freeze".

There's no way around it: you must create a dedicated thread for the server loop to run in. You probably have to do the same thing for the client, if the client sits in a loop reading and writing. Since you're apparently already creating threads to handle the server connections, this shouldn't be a problem for you.

[Jess in Action][AskingGoodQuestions]
Karel Tevarnier

Joined: Apr 21, 2006
Posts: 2
thanks for the quick reply's

I was already thinking to put the server in another thread on its own.

Here's the full program (some names are in dutch):


It's a project for school. Other people made it by starting te whole program 2 times, first selecting server and connect, second selecting client and connect.

If I should do it like them now, I'll have to rewrite the whole thing.
I agree. Here's the link: http://aspose.com/file-tools
subject: Gui freezes only when using multiple frames and 'while' socket is listening
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