자바 NIO 셀렉터

Server.java

import java.io.IOException;

import java.net.InetSocketAddress;

import java.nio.ByteBuffer;

import java.nio.channels.SelectionKey;

import java.nio.channels.Selector;

import java.nio.channels.ServerSocketChannel;

import java.nio.channels.SocketChannel;

import java.nio.charset.Charset;

import java.util.Iterator;

import java.util.List;

import java.util.Set;

import java.util.Vector;

public class IotServer {

Selector selector;

ServerSocketChannel serverSocketChannel;

List<Client> connections = new Vector<Client>();

void startServer() {

try {

selector = Selector.open();

serverSocketChannel = ServerSocketChannel.open();

serverSocketChannel.configureBlocking(false);

serverSocketChannel.bind(new InetSocketAddress(5001));

serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);

} catch (Exception e) {

if(serverSocketChannel.isOpen()) { stopServer(); }

return;

}

Thread thread = new Thread() {

@Override

public void run() {

while(true) {

try {

int keyCount = selector.select();

if(keyCount == 0) { continue; }

Set<SelectionKey> selectedKeys = selector.selectedKeys();

Iterator<SelectionKey> iterator = selectedKeys.iterator();

while (iterator.hasNext()) {

SelectionKey selectionKey = iterator.next();

if (selectionKey.isAcceptable()) {

accept(selectionKey);

} else if (selectionKey.isReadable()) {

Client client = (Client)selectionKey.attachment();

client.receive(selectionKey);

} else if (selectionKey.isWritable()) {

Client client = (Client)selectionKey.attachment();

client.send(selectionKey);

}

iterator.remove();

}

} catch (Exception e) {

if(serverSocketChannel.isOpen()) { stopServer(); }

break;

}

}

}

};

thread.start();

System.out.println("서버 멈춤");

}

void stopServer() {

try {

Iterator<Client> iterator = connections.iterator();

while(iterator.hasNext()) {

Client client = iterator.next();

client.socketChannel.close();

iterator.remove();

}

if(serverSocketChannel!=null && serverSocketChannel.isOpen()) { 

serverSocketChannel.close(); 

}

if(selector!=null && selector.isOpen()) {

selector.close();

}

System.out.println("서버 멈춤");

} catch (Exception e) {}

}

void accept(SelectionKey selectionKey) {

try {

ServerSocketChannel serverSocketChannel = (ServerSocketChannel) selectionKey.channel();

SocketChannel socketChannel = serverSocketChannel.accept();

String message = "[연결 수락: " + socketChannel.getRemoteAddress()  + ": " + Thread.currentThread().getName() + "]";

System.out.println(message);

Client client = new Client(socketChannel);

connections.add(client);

System.out.println("[연결 개수: " + connections.size() + "]");

} catch(Exception e) {

if(serverSocketChannel.isOpen()) { stopServer(); }

}

}

class Client {

SocketChannel socketChannel;

String sendData;

Client(SocketChannel socketChannel) throws IOException {

this.socketChannel = socketChannel;

socketChannel.configureBlocking(false);

SelectionKey selectionKey = socketChannel.register(selector, SelectionKey.OP_READ);

selectionKey.attach(this);

}

void receive(SelectionKey selectionKey) {

try {

ByteBuffer byteBuffer = ByteBuffer.allocate(100);

//상대방이 비정상 종료를 했을 경우 자동 IOException 발생

int byteCount = socketChannel.read(byteBuffer); 

//상대방이 SocketChannel의 close() 메소드를 호출할 경우

if(byteCount == -1) { 

throw new IOException();

}

String message = "[요청 처리: " + socketChannel.getRemoteAddress() + ": " + Thread.currentThread().getName() + "]";

System.out.println(message);

byteBuffer.flip();

Charset charset = Charset.forName("UTF-8");

String data = charset.decode(byteBuffer).toString();

System.out.println(data);

for(Client client : connections) {

client.sendData = data;

SelectionKey key = client.socketChannel.keyFor(selector);

key.interestOps(SelectionKey.OP_WRITE);

}

selector.wakeup();

String[] receivedMessage = null;

receivedMessage = data.split("#");   

System.out.println(receivedMessage[0]+"\n"+receivedMessage[1]);

if(receivedMessage[0].equals("hello")){

if(receivedMessage[1].equals("server")) {

System.out.println("split");

}

}

} catch(Exception e) {

try {

connections.remove(this);

String message = "[클라이언트 통신 안됨: " + socketChannel.getRemoteAddress() + ": " + Thread.currentThread().getName() + "]";

System.out.println(message);

socketChannel.close();

} catch (IOException e2) {}

}

}

void send(SelectionKey selectionKey) {

try {

Charset charset = Charset.forName("UTF-8");

ByteBuffer byteBuffer = charset.encode(sendData);

socketChannel.write(byteBuffer);

selectionKey.interestOps(SelectionKey.OP_READ);

selector.wakeup();

} catch(Exception e) {

try {

String message = "[클라이언트 통신 안됨: " + socketChannel.getRemoteAddress() + ": " + Thread.currentThread().getName() + "]";

System.out.println(message);

connections.remove(this);

socketChannel.close();

} catch (IOException e2) {}

}

}

}

public static void main(String[] args) {

IotServer server = new IotServer();

server.startServer();

}

}