Multithreading Socket communication Client/Server

Question

I finished writing a Client/Server Socket communication program that works fine. Now I'm trying to figure out how to make it so that I can have multiple Client connections to the Server at once. I've looked around and there seems to be more than a couple of different ways to do this. so I've come here to ask you guys for help/suggestions. My Server: ``` public class Server { private ServerSocket serverSocket = null; private Socket clientSocket = null; public Server() { try { serverSocket = new ServerSocket(7003); } catch (IOException e) { System.err.println("Could not listen on port: 7003"); System.exit(1); } try { clientSocket = serverSocket.accept(); } catch (IOException e) { System.err.println("Accept failed"); System.exit(1); } } public void startServer() throws IOException { PrintWriter output = new PrintWriter(clientSocket.getOutputStream(), true); BufferedReader input = new BufferedReader(new InputStreamReader(clientSocket.getInputStream())); String inputLine, outputLine; outpu…

Accepted Answer

You should use `ExecutorService`. Your client request processing would be the `run()` of a `Runnable` and after each accept you can call `ExecutorService.submit(runnableTask)` to asynchronously service the client. A sample using ExecutorService.

```
public class MyServer {

private static MyServer server; 
    private ServerSocket serverSocket;

/**
     * This executor service has 10 threads. 
     * So it means your server can process max 10 concurrent requests.
     */
    private ExecutorService executorService = Executors.newFixedThreadPool(10);

public static void main(String[] args) throws IOException {
        server = new MyServer();
        server.runServer();
    }

private void runServer() {        
        int serverPort = 8085;
        try {
            System.out.println("Starting Server");
            serverSocket = new ServerSocket(serverPort);

while(true) {
                System.out.println("Waiting for request");
                try {
                    Socket s = serverSocket.accept();
                    System.out.println("Processing request");
                    executorService.submit(new ServiceRequest(s));
                } catch(IOException ioe) {
                    System.out.println("Error accepting connection");
                    ioe.printStackTrace();
                }
            }
        }catch(IOException e) {
            System.out.println("Error starting Server on "+serverPort);
            e.printStackTrace();
        }
    }

//Call the method when you want to stop your server
    private void stopServer() {
        //Stop the executor service.
        executorService.shutdownNow();
        try {
            //Stop accepting requests.
            serverSocket.close();
        } catch (IOException e) {
            System.out.println("Error in server shutdown");
            e.printStackTrace();
        }
        System.exit(0);
    }

class ServiceRequest implements Runnable {

private Socket socket;

public ServiceRequest(Socket connection) {
            this.socket = connection;
        }

public void run() {

//Do your logic here. You have the `socket` available to read/write data.

//Make sure to close
            try {
                socket.close();
            }catch(IOException ioe) {
                System.out.println("Error closing client connection");
            }
        }        
    }
}
```

Multithreading Socket communication Client/Server

Solution

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