Chapter.10 미션B 완료

- Mission B: Busy-Waiting Non-Blocking Server

Co-authored-by: famo1245 <kandallee38@gmail.com>

chapter10/missionB/MissionB.java

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+package chapter10.missionB;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.InetSocketAddress;
+import java.net.ServerSocket;
+import java.net.Socket;
+import java.net.SocketTimeoutException;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.Set;
+
+public class MissionB {
+
+    public static void main(String[] args) {
+        Server server = new Server();
+        server.start();
+    }
+
+    private static class Server {
+
+        private static final int BUFFER_SIZE = 1024;
+        private static final String HOST = "127.0.0.1";
+        private static final int PORT_NUM = 12345;
+
+        private ServerSocket serverSocket;
+        private final Set<SocketHandler> clients = new HashSet<>();
+
+        public void start() {
+            try {
+                serverSocket = new ServerSocket();
+                serverSocket.bind(new InetSocketAddress(HOST, PORT_NUM));
+                serverSocket.setSoTimeout(200);
+                System.out.println("Server listening for incoming connections");
+
+                while (true) {
+                    accept();
+                    serveAllClients();
+                }
+            } catch (IOException e) {
+                System.err.println("Server error: " + e.getMessage());
+            } finally {
+                closeServer();
+            }
+        }
+
+        private void closeServer() {
+            clients.forEach(SocketHandler::close);
+            clients.clear();
+
+            try {
+                if (serverSocket != null && !serverSocket.isClosed()) {
+                    serverSocket.close();
+                }
+            } catch (IOException e) {
+                System.err.println("Server error with closing: " + e.getMessage());
+            }
+            System.out.println("Server stopped");
+        }
+
+        private void serveAllClients() {
+            Iterator<SocketHandler> iterator = clients.iterator();
+
+            while (iterator.hasNext()) {
+                SocketHandler client = iterator.next();
+                if (!client.handle()) {
+                    iterator.remove();
+                    client.close();
+                }
+            }
+        }
+
+        private void accept() {
+            try {
+                Socket client = serverSocket.accept();
+                client.setSoTimeout(200);
+                clients.add(new SocketHandler(client));
+                System.out.println("Connected to " + client.getRemoteSocketAddress());
+            } catch (SocketTimeoutException ignored) {
+            } catch (IOException e) {
+                System.err.println("accept: " + e.getMessage());
+            }
+        }
+
+        private static class SocketHandler {
+
+            private final Socket socket;
+            private final byte[] buffer;
+
+            public SocketHandler(Socket socket) {
+                this.socket = socket;
+                buffer = new byte[BUFFER_SIZE];
+            }
+
+            public boolean handle() {
+                try {
+                    InputStream in = socket.getInputStream();
+
+                    if (in.available() > 0) {
+                        int bytesRead = in.read(buffer);
+
+                        if (bytesRead == -1) {
+                            return false;
+                        }
+
+                        String message = new String(buffer, 0, bytesRead).trim();
+                        String response;
+                        try {
+                            int order = Integer.parseInt(message);
+                            response = "Thank you for ordering " + order + " pizzas!\n";
+                        } catch (NumberFormatException e) {
+                            response = "Wrong number of pizzas, please try again\n";
+                        }
+
+                        System.out.println("Sending message to " + socket.getRemoteSocketAddress());
+                        socket.getOutputStream().write(response.getBytes());
+                    }
+                    return true;
+                } catch (IOException e) {
+                    System.err.println("Socket error: " + e.getMessage());
+                    return false;
+                }
+            }
+
+            public void close() {
+                try {
+                    if (socket != null && !socket.isClosed()) {
+                        System.out.println("Closing " + socket.getRemoteSocketAddress());
+                        socket.close();
+                    }
+                } catch (IOException e) {
+                    System.err.println("Error with closing client connection: " + e.getMessage());
+                }
+            }
+        }
+    }
+}