Day 19 - Java 네트워크(java.net)

InetAddress

java.net.InetAddress inet01 = null;

String host = "google.com";

try {
    inet01 = InetAddress.getByName(host);
    System.out.println(inet01.getHostName()); // google.com
    System.out.println(inet01.getHostAddress()); // 142.250.206.206
    System.out.println(inet01.getCanonicalHostName()); // kix07s07-in-f14.1e100.net - 실질 서버 
} catch (UnknownHostException e) {
    e.printStackTrace();
}

java.net.InetAddress[] inets = null;

String host = "daum.net";

try {
    inets = InetAddress.getAllByName(host);
    for(int i = 0; i < inets.length; i++) {
        InetAddress inet = inets[i];
    System.out.println(inet.getHostName()); 
    System.out.println(inet.getHostAddress()); 
    System.out.println(inet.getCanonicalHostName()); 
    }
} catch (UnknownHostException e) {
    e.printStackTrace();
}

// 0.0.0.0 ~ 255.255.255.255 (4byte의 주소 체계)
byte[] addr = new byte[] {(byte)172, (byte)217, (byte)161, (byte)238};
inet01 = InetAddress.getByAddress(addr);
System.out.println(inet01.getHostName()); 
System.out.println(inet01.getHostAddress()); 

java.net.URL url = null;
try {
    String path = "https://getbootstrap.com/docs/3.4/components/#navbar";
    url = new URL(path);
    System.out.println(url.getProtocol()); // https
    System.out.println(url.getHost()); // getbootstrap.com
    System.out.println(url.getPort()); // -1
    System.out.println(url.getDefaultPort()); // 443
    System.out.println(url.getFile()); // /docs/3.4/components/
    System.out.println(url.getPath()); // /docs/3.4/components/
    System.out.println(url.getQuery()); // null
    System.out.println(url.getAuthority()); // getbootstrap.com
    System.out.println(url.getRef()); // navbar
} catch (MalformedURLException e) {
    e.printStackTrace();
}

java.net.URLConnection conn = null;
java.net.URL url= null;

java.io.InputStream is = null;
java.io.InputStreamReader isr = null;

String spec = "https://google.com";

try {
    url = new URL(spec);
    conn = url.openConnection(); // 서버에 접속
    is = conn.getInputStream();
    isr = new InputStreamReader(is);

    while(true) {
        int su = isr.read();
        if(su == -1) break;
        System.out.print((char)su);
    }

    isr.close();
    is.close();

} catch (IOException e) {
    e.printStackTrace();
}        

web scrapping 하기

java.net.URLConnection conn = null;
java.net.URL url= null;

java.io.InputStream is = null;
java.io.InputStreamReader isr = null;

String spec = "https://google.com";
File f = new File("google.html");

OutputStream os = null;

try {
    os = new FileOutputStream(f);

    url = new URL(spec);
    conn = url.openConnection(); // 서버에 접속
    is = conn.getInputStream();

    while(true) {
        int su = is.read();
        if(su == -1) break;
        os.write(su);
    }

    os.close();
    is.close();

} catch (IOException e) {
    e.printStackTrace();
}

java.net.URLConnection conn = null;
java.net.URL url= null;

InputStream is = null;
InputStreamReader isr = null;

String spec = "https://daum.net";

OutputStream os = null;
try {
    url = new URL(spec);
    conn = url.openConnection(); // 서버에 접속
    is = conn.getInputStream();
    isr = new InputStreamReader(is, "UTF-8");
            String msg = "";

    while(true) {
        int su = isr.read();
        if(su == -1) break;
        System.out.print((char)su);
        msg += ((char)su);
    }

    System.out.println("완료");

    int beginIdx = msg.indexOf("인덱스 문장");
    int endIdx = msg.indexOf("<!-- 인덱스 문장 -->");
    msg = msg.substring(beginIdx, endIdx);
    msg = msg.replaceAll("\t", "");
    System.out.println(msg);

    isr.close();
    is.close();

} catch (IOException e) {
    e.printStackTrace();
}

다운로드 프로그램 만들기

java.net.URLConnection conn = null;
java.net.URL url= null;

InputStream is = null;
InputStreamReader isr = null;

String spec = "https://www.7-zip.org/a/7z2408-x64.exe";
File f = new File("7z.exe");

OutputStream os = null;

try {
    os = new FileOutputStream(f);

    url = new URL(spec);
    conn = url.openConnection(); // 서버에 접속
    is = conn.getInputStream();

    while(true) {
        int su = is.read();
        if(su == -1) break;
        os.write(su);
    }
    System.out.println("다운로드 완료");
    os.close();
    is.close();

} catch (IOException e) {
    e.printStackTrace();
}

Buffer를 사용한 다운로드 속도 올리기

java.net.URLConnection conn = null;
java.net.URL url= null;

InputStream is = null;
InputStreamReader isr = null;

String spec = "https://www.7-zip.org/a/7z2408-x64.exe";
File f = new File("7z_1.exe");

OutputStream os = null;

BufferedInputStream    bis = null;
BufferedOutputStream    bos = null;
try {
    os = new FileOutputStream(f);
    url = new URL(spec);
    conn = url.openConnection(); // 서버에 접속
    is = conn.getInputStream();
    bis = new BufferedInputStream(is);
    bos = new BufferedOutputStream(os);
    byte[] buf = new byte[512];

    while(true) {
        int su = is.read(buf);
        if(su == -1) break;
        os.write(buf, 0, su);
    }

    System.out.println("다운로드 완료");
    bos.close();
    bis.close();
    os.close();
    is.close();

} catch (IOException e) {
    e.printStackTrace();
}

host

• DNS에 ip 주소를 물어보기 전 호스트 파일이 더 우선순위에 있다.
• 우선순위: hosts -> node Root -> DNS

C:\Windows\System32\drivers\etc

---

---

채팅 프로그램 만들기

• HW : 1 ~ 2 계층
• OS(SW) : 3 ~ 4 계층
• SW : 5 ~ 7 계층

TCP / UDP

• tcp: 순서를 보장 (대체로 사용되는 방식)
• udp: 순서를 보장하지 않음. 피켓이 loss될 수도 있음 (예: 방송 송출)

port

• 물리적인 포트와 개념적인 포트가 존재한다.
• 송수신하는 데이터의 유형을 관리
• 관문 역할을 한다.(예: 방화벽)

서버와 클라이언트 만들기

기본

Server

public class Server{

    public static void main(String[] args) {
        int port = 5000;
        ServerSocket serv = null;
        Socket sock = null;

        InputStream is = null;
        OutputStream os = null;

        try {
            serv = new ServerSocket(port);
            System.out.println("waiting to connect...");

            sock = serv.accept();
            InetAddress addr = sock.getInetAddress();
            is = sock.getInputStream();
            os = sock.getOutputStream();
            byte[] buf = new byte[10];
            is.read(buf);
            System.out.println("connecting to... " + addr.getHostAddress());
            System.out.println(new String(buf));
            os.write("welcome".getBytes());
            os.write(255);

            while(true) {
                int su = is.read();
                if(su == -1) break;
                System.out.print((char)su);
            }

        } catch (IOException e) {
            e.printStackTrace();
        }finally {
                try {
                    if(os != null) os.close();
                    if(is != null) is.close();
                    if(sock != null) sock.close();
                    if(serv != null) serv.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
        }
    }
}

Client

public class Client {

    public static void main(String[] args) {

        int port = 5000;
        Socket sock = null;

        OutputStream os = null;
        InputStream is = null;

        byte[] ip = new byte[] {(byte)192, (byte)168, (byte)219, (byte)125};

        try {

            InetAddress addr = InetAddress.getByAddress(ip);
            sock = new Socket(addr, port);
            os = sock.getOutputStream();
            is = sock.getInputStream();
            os.write("hello java".getBytes());

            while(true) {
                int su = is.read();
                if(su == 255) break;
                System.out.print((char)su);
            }
            os.write("me too".getBytes());

        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                if(is != null) is.close();
                if(os != null) os.close();
                if(sock != null) sock.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }
}

하나의 클라이언트와 통신하는 서버 (InputStreamReader)

Server

public class Server {

    public static void main(String[] args) {
        int port = 5000;
        ServerSocket serv = null;

        InputStream is = null;
        InputStreamReader isr = null;
        BufferedReader br = null;

        try {
            serv = new ServerSocket(port);
            while(true) {
                Socket sock = serv.accept();
                is = sock.getInputStream();
                isr = new InputStreamReader(is);
                br = new BufferedReader(isr);
                while(true) {
                    String msg = br.readLine();

                    System.out.println(sock.getInetAddress().getHostAddress() + " >> " + msg);
                }

            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                if(is != null) is.close();
                if(serv != null) serv.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }
}

Client

public class Client {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int port = 5000;
        Socket sock = null;

        OutputStream os = null;
        PrintStream ps = null;

        try {

            sock = new Socket(InetAddress.getByAddress(new byte[] {(byte)192, (byte)168, 54, 90}), port);
            os = sock.getOutputStream();
            ps = new PrintStream(os);

            while(true) {
                System.out.print("client >> ");
                String msg = sc.nextLine();
//                ps.println(msg);
                ps.write(msg.getBytes());
                ps.write("\n".getBytes());
                ps.flush();
            }

        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                if(ps != null) ps.close();
                if(os != null) os.close();
                if(sock != null) sock.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }
}

여러 클라이언트와 통신하는 서버

Server

public class Server extends Thread{
    Socket sock;

    public Server(Socket sock) {
        this.sock = sock;
    }

    @Override
    public void run() {
        String ip = sock.getInetAddress().getHostAddress();
        try(
                InputStream is = sock.getInputStream();
                OutputStream os = sock.getOutputStream();
                InputStreamReader isr = new InputStreamReader(is);
                BufferedReader br = new BufferedReader(isr);
                PrintStream ps = new PrintStream(os)
                ){
            while(true) {
                String msg = br.readLine();
                ps.println(ip + " >> " + msg);
                ps.flush();
            }

        } catch (IOException e) {
                    e.printStackTrace();
                }
    }

    public static void main(String[] args) {
        int port = 5000;

        ServerSocket serv = null;

        try {

            serv = new ServerSocket(port);

            while(true) {
                Socket sock = serv.accept();
                Server thr = new Server(sock);
                thr.start();
            }

        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                if(serv != null) serv.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }
}

Client

public class Client {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int port = 5000;
        Socket sock = null;

        OutputStream os = null;
        InputStream is = null;
        PrintStream ps = null;
        InputStreamReader isr = null;
        BufferedReader br = null;

        try {

            sock = new Socket(InetAddress.getByAddress(new byte[] {(byte)192, (byte)168, 54, 90}), port);
            os = sock.getOutputStream();
            ps = new PrintStream(os);
            is = sock.getInputStream();
            isr = new InputStreamReader(is);
            br = new BufferedReader(isr);

            while(true) {
                System.out.print("client >> ");
                String msg = sc.nextLine();
                ps.println(msg);
                ps.flush();
                String result = br.readLine();
                System.out.println(result);
            }

        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                if(ps != null) ps.close();
                if(os != null) os.close();
                if(sock != null) sock.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }
}

UI 를 사용한 채팅 프로그램 만들기, 클라이언트가 나갈때 에러 없애기

Server

public class Server implements Runnable{
    Socket sock;
    static ArrayList<Socket> list;

    public Server(Socket sock) {
        this.sock = sock;
    }

    public void sendAll(String msg) {

        for(int i = 0; i < list.size(); i++) {
            Socket sock = list.get(i);
            try {
                OutputStream os = sock.getOutputStream();
                PrintStream ps = new PrintStream(os);
                ps.println(msg);
                ps.flush();
            } catch (IOException e) {
                list.remove(sock);
            }
        }
    }

    @Override
    public void run() {

        try {
            InputStream is = sock.getInputStream();
            InputStreamReader isr = new InputStreamReader(is);
            BufferedReader br = new BufferedReader(isr);
            while(true) {
                String msg = br.readLine();
                sendAll(sock.getInetAddress().getHostAddress() + ">>" + msg);
                }
        } catch (IOException e) {
            list.remove(sock);
        }
    }

    public static void main(String[] args) {
         list = new ArrayList<>();

        try(
                ServerSocket serv = new ServerSocket(6000);
                ) {
            while(true) {
                Socket sock = serv.accept();
                Server me = new Server(sock);

                Thread thr = new Thread(me);
                thr.start();
                list.add(sock);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

    }
}

=> 클라이언트 인덱스를 ip주소로 받으면 클라이언트가 나가도 index가 바뀌지 않는다.

Client

public class Client extends Frame implements ActionListener{
    TextField tf;
    static PrintStream ps;

    public Client() {
        tf = new TextField();
        tf.addActionListener(this);
        add(tf);
        setBounds(600, 300, 300, 100);
        setVisible(true);
    }

    public static void main(String[] args) {
        Client me = new Client();

        int port = 6000;

        try(
                Socket sock = new Socket("127.0.0.1", port);
                InputStream is = sock.getInputStream();
                OutputStream os = sock.getOutputStream();
                InputStreamReader isr = new InputStreamReader(is);
                BufferedReader br = new BufferedReader(isr);
                ) {
            ps = new PrintStream(os);
            while(true) {
                String msg = br.readLine();
                System.out.println(msg);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        String msg = tf.getText();
        ps.println(msg);
        ps.flush();
        tf.setText("");
    }
}