CODEWITHSUNDEEP
javaswingsockets
shep
shep

Reputation: 523

JFrame blocked after creating socket connection

so i've been trying to learn about sockets, and was trying to create a simple chat app where i have 2 JFrames and each connects to socket, the problem is that every time i run the JFrames the frames start correctly, but when i click on the connect_button the socket starts connection but doesn't let me continue with the operations, everything is blocked from this point forward, i've been realy trying to understand but im stuck here, any thoughts ?

  1. i think my problem is that the sockets should go in their own Threads, but i've seen other solutions and seen that they don't implement Threads, or at least in the code that they show.

  2. maybe my socket connection is implemented incorrectly.

¿Is it wrong to use PrintStream if so, is it still posible to use this class to proceed with this excercise and which Stream class should i use ? Taking into count that i understand that bufferedStreams are the way to go if you want efficiency

Upvotes: 0

Views: 527

Answers (3)

Subhrajyoti Majumder
Subhrajyoti Majumder

Reputation: 41200

If you retain your GUI thread to make socket communication it is for sure, this will block your thread(UI).

What is required is some async or non blocking way to make socket communication, which does not block your GUI thread.

Keep your GUI thread separate and runs on its own and make socket connection through creating FutureTask or ForkJoinTask or Thread or non blocking socket communication which updates once you received communication message.

Example to create non blocking socket

Upvotes: 0

MadProgrammer
MadProgrammer

Reputation: 347214

Swing is not thread safe. That is, all UI events occur within the context of the Event Dispatching Thread, including paint events.

Anything that blocks this thread will prevent the EDT from processing new events and essentially make your application look like it's hung.

Take a look at Concurrency in Swing for more details...

The call to initServerConnector in the actionPerformed method of the Messenger_Controller class is creating a new Conector which is creating a ServerSocket and calling accept on it, which is a blocking method. This is preventing the EDT from processing new events until it returns.

Instead, you should be using either a SwingWorker or Thread to manage the Socket connections and communications.

See Worker Threads and SwingWorker for more details.

Swing components should also not be updated from outside the context of the EDT. This means if you need to make changes to the UI while processing the socket comms, you will need to sync those updates back to the UI.

If you're using a SwingWorker, you can use the publish/process methods or you will need to use SwingUtilities.invokeLater, both approaches will sync the calls back to the EDT where you can makes changes safely...

Upvotes: 1

icza
icza

Reputation: 417662

You create your socket and handle network traffic in the EDT (Event Dispatching Thread) because you do this in an ActionListener. This is the same thread that is used to paint the GUI of your application and handle interactions with the user.

You should not do lengthy task in the EDT but start a new thread for them.

Upvotes: 0

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