Java 소켓을 사용하여 단체 채팅방 만들기

실행 결과

ChatServer

 

ChatClient 1

 

ChatClient 2

---

ChatServer

import java.io.*;
import java.net.*;
import java.util.*;
 
public class ChatServer {
    private static Set<ClientHandler> clients = new HashSet<>();
    private static final int PORT = 5000;
 
    public static void main(String[] args) {
        try (ServerSocket serverSocket = new ServerSocket(PORT)) {
            System.out.println("SERVER START. Listening port " + PORT);
 
            while (true) {
                Socket clientSocket = serverSocket.accept();
                
                System.out.println("New client connected: " + clientSocket);
                ClientHandler clientHandler = new ClientHandler(clientSocket);
                clients.add(clientHandler);
 
                Thread ClientThread = new Thread(clientHandler);
                ClientThread.start();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
 
    private static class ClientHandler implements Runnable {
        private Socket clientSocket;
        private BufferedReader reader;
        private PrintWriter writer;
 
        public ClientHandler(Socket clientSocket) {
            this.clientSocket = clientSocket;
            try {
                reader = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                writer = new PrintWriter(clientSocket.getOutputStream(), true);
                writer.println("Connected to server. Input Your Name: ");
                writer.flush();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
 
        @Override
        public void run() {
        	String clientName = null;
            try {
            	
            	boolean isFirstEntry = true;
                String clientMessage;
                
                // 클라이언트가 메시지 입력할 때 마다 수행
                while ((clientMessage = reader.readLine()) != null) {
                	if(isFirstEntry) {
                		clientName = clientMessage;
                		isFirstEntry = false;
                		broadcastMessage(clientName + " has entered");
                		continue;
                	}
                	
                    System.out.println(clientName + "(" + new Date() + "): " + clientMessage);
                    broadcastMessage(clientName + ": " + clientMessage);
                }
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                closeConnection(clientName);
            }
        }
 
        private void broadcastMessage(String message) {
            synchronized (clients) {
                for (ClientHandler client : clients) {
        			client.writer.println(message);
                }
            }
        }
 
        private void closeConnection(String clientName) {
            try {
                clients.remove(this);
                reader.close();
                writer.close();
                clientSocket.close();
                System.out.println("Connection closed: " + clientSocket + " (" + clientName + ")");
                broadcastMessage(clientName + " left");
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

---

ChatClient

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
 
public class ChatClient {
    private static final String SERVER_ADDRESS = "127.0.0.1";
    private static final int SERVER_PORT = 5000;
 
    private Socket socket;
    private BufferedReader reader;
    private PrintWriter writer;
 
    public static void main(String[] args) {
        ChatClient client = new ChatClient();
        client.start();
    }
 
    public void start() {
        try {
            socket = new Socket(SERVER_ADDRESS, SERVER_PORT);
            reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            writer = new PrintWriter(socket.getOutputStream(), true);
 
            Thread receiveThread = new Thread(() -> {
            	receiveMessages();
            });
            receiveThread.start();
 
            BufferedReader consoleReader = new BufferedReader(new InputStreamReader(System.in));
 
            String userInput;
            while ((userInput = consoleReader.readLine()) != null) {
                if (userInput.equalsIgnoreCase("exit")) {
                    writer.println(userInput);
                    break;
                }
                writer.println(userInput);
            }
 
            System.out.println("Disconnected from server");
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            closeResources();
        }
    }
 
    private void receiveMessages() {
        try {
            String message;
            while ((message = reader.readLine()) != null) {
                System.out.println(message);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            closeResources();
        }
    }
 
    private void closeResources() {
        try {
            if (writer != null)
                writer.close();
            if (reader != null)
                reader.close();
            if (socket != null)
                socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}