CODEWITHSUNDEEP
javamultithreadingsockets
marcuthh
marcuthh

Reputation: 596

Java - Recognise sent-to-one and sent-to-all messages from server, on the client-side

I am working on a server/client application that allows multiple clients to be connected to the server at any given time. For each client, the server sets up a ClientHandler object that has an input and output stream to the client connected at this socket. Through this connection, the client is free to send a number of messages to the server at any point throughout the running of the program, and the server will respond according to the message.

What I need to implement is a mechanism that sends, at certain times, messages to all currently-connected clients. I have done this by storing all the output streams to clients in an ArrayList<PrintWriter> that will allow the same message to be sent to all clients.

What I am struggling with is this:

When a message is received that is individual to the client, the client GUI is updated accordingly (only a select number of messages can be sent, so there only a select number of possible responses-from-server, dealt with by client-side if statements). However, when a message is received by the client that was sent to all clients, I would like the client to update the GUI quite differently.

Considering that both forms of input come from the same input stream, I can see this being difficult, and I anticipate that I will have to declare any methods that cause output using the PrintWriter will have to be made synchronized. However, is there a way to process the different inputs while using the same PrintWriter at all? Would this have to be done using further if statements or could it be done using a separate Thread on the client side that handles messages sent to all clients?

Thanks for any advice, if you think you can help then feel free to ask for parts of my existing code!

Mark

Upvotes: 3

Views: 261

Answers (2)

Mohammad Muddasir
Mohammad Muddasir

Reputation: 975

     When your clients connect to the server, your server creates a Socket for it, here it is Socket socket = ss.accept();, your socket variable will be holding that client.

now if you just keep adding your client socket to a arraylist in your while loop, you will have a list of clients actively connected with your server like:

after the accept:

  clients = new ArrayList<DataOutputStream>();
  Socket socket = ss.accept();
  os = new DataOutputStream(socket.getOutputStream());
  clients.add(os);

Now as you have all the clients in that clients arraylist, you can loop through it, or with some protocol define which client should i send the data after reading.

Upvotes: 1

rpy
rpy

Reputation: 4023

You are first of all lacking a protocol between your server and your clients!

Obviously the server can send two types of messages "response" and "broadcast". A rather simple approach is tagging your messages: e.g. prefix your mesages with "R" if it is a response to a request and with "B" if it is an unattended broadcast message. (This all depends how communication between server and clients is intended to be performed.)

Whether your client needs different threads for coping with the messages is a completly different story. Having different threads is useful if the processing activity within your client would prevent timely reads of the socket. Then you might consider having an I/O thread that is doing communications and is dispatching the messages to different "handlers" (could be other threads) for processing. (This I/O thread also can remove the tag such that existing processing code need not learn about the lower protocol with the server.)

An analogous reasoning might apply to your server side. Depending on the dynamics of interactions and processing of requests, you might use several threads. Then you should have one that is doing I/O with the clients and others that are doing the work (generating responses or broadcast messages)

Upvotes: 3

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