asked on

Server programming question

I'm writing a server in java that uses threads to have multiple clients connect to the same serversocket. My question is this: How can I exchange info between the connected clients?

For instance, if there are 3 clients connected, and clientA sends some information to the server; how can I have the server send that info to ALL the connected clients?

Here is what my server looks like:
ServerSocket server_socket;
try{
server_socket = new ServerSocket(1000);
} catch (IOException e) {
System.out.println("Could not listen on port 1000");
System.exit(-1);
}
while(true){
ServerThread newConnection;
try{
newConnection = new serverThread(server_socket.accept());
newConnection.start();
} catch (IOException e) {
System.out.println("Accept failed: 4444");
System.exit(-1);
}
}

fivesigmaevent

You could try to pass a shared buffer to the thread constructor.

newConnection = new serverThread(server_socket.accept(), sharedBuffer );

Use the buffer to communicate between threads. You probably should synchronize access to the buffer so not to corrupt any data.

lwinkenb

ASKER

Im not really sure how a shared buffer works. Could you point me to an example?

warsql

Sounds like an event model is what you are looking for. The server could keep a list of ServerThread connections and notify each whenever a message comes in. Just make sure to remove the ServerThread from the list when closed to avoid a memory leak.

lwinkenb

ASKER

could you post an example to get me started warsql?

ASKER CERTIFIED SOLUTION

warsql

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fivesigmaevent

I was going to change what I said about passing a buffer to passing "this" and invoking a callback for each thread. Looks like warsql beat me to it!

This community is awesome.

lwinkenb

ASKER

Thanks a lot, perfect answer.

warsql

After further thought, the connections variable will be accessed by different threads, so you will want to synchronize around its access.

synchronized(connections) {
// add to connections
}

and

syncronized(connections) {
// iterate through connections
}

just in case a client connects while a message is being broadcast.