[Java] 네트워크 프로그래밍

public void startServer() {
    ServerSocket server = null;
    Socket client = null;
    
    try {
        server = new ServerSocket(9999);
        
        while(true) {
            System.out.println("Server:Waiting for request.");
            client = server.accept();
            System.out.println("Server:Accepted.");
            InputStream stream = client.getInputStream();
            
            // 받은 데이터 처리
            BufferedReader in = new BufferedReader(new InputStreamReader(stream));
            String data = null;
            StringBuilder receiveData = new StringBuilder();
            while((data = in.readLine()) != null) {
                receivedData.append(data);
            }
            System.out.println("Received data:"+receivedData);
            in.close();
            
            client.close();
            
            if(receivedData != null && "EXIT".equals(receivedData.toString())) {
                break;
            }
        }
        
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        if(server != null) {
            server.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

public void sendSocketData(String data) {
    Socket socket = null;
    try {
		System.out.println("Cleint:Connecting");
        socket = new Socket("127.0.0.1", 9999);
        System.out.println("Cleint:Connect status=" + socket.isConnected());
        Thread.sleep(1000);
        OutputStream stream = socket.getOutputStream();
        
        // 보내는 데이터 처리
        BufferedOutputStream out = new BufferedOutputStream(stream);
        byte[] bytes = data.getBytes();
        out.write(bytes);
		System.out.println("Client:Sent data");
        out.close();
        
    } catch(Exception e) {
        e.printStackTrace();
    } finally {
        if(socket != null) {
            try {
                socket.close();
            } catch(Exception e) {
                e.printStackTrace();
            }
        }
    }
}

public void startServer() {
    DatagramSocket server = null;
    try {
        server = new DatagramSocket(9999);
        int bufferLength = 256;
        byte[] buffer = new byte[bufferLength];
        DatagramPacket packet = new DatagramPacket(buffer, bufferLength);
        while(true) {
            System.out.println("Server:Waiting for request.");
            server.receive(packet);
            int dataLength = packet.getLength();
            System.out.println("Server:received. Data length=" + dataLength);
            String data = new String(packet.getData(), 0, dataLength);
            System.out.println("Received data:" + data);
            if(data.equals("EXIT")) {
				break;
            }
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        if(server != null) {
            try {
                server.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

public void sendDatagramData(String data) {
    try {
        DatagramSocket client = new DatagramSocket();
        InetAddress address = InetAddress.getByName("127.0.0.1");
        byte[] buffer = data.getBytes();
        DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length, address, 9999);
        client.send(packet);
        System.out.println("Cleint:Sent data");
        client.close();
        Thread.sleep(1000);
    } catch(Exception e) {
        e.printStackTrace();
    }
}