13. Networking

1

public class SumTest { public static void main(String a1[]) { int a, b, sum; a = Integer.parseInt(a1[0]); b = Integer.parseInt(a1[1]); sum = a + b ; // 두 수를 더하는 부분입니다 System.out.println(" 두수의 합은 " + sum + " 입니다 "); }}

JAVA

2

Client/Server Communica-tions

Server Host

Server socket on port 8000 SeverSocket server = new ServerSocket(8000);

A client socket Socket socket = server.accept()

Client Host

Client socket Socket socket = new Socket(host, 8000)

I/O Stream

The server must be running when a client starts. The server waits for a connection request from a client. To establish a server, you need to create a server socket and attach it to a port, which is where the server listens for connections.

After a server socket is created, the server can use this statement to listen for connections.

The client issues this statement to request a connection to a server.

After the server accepts the connection, communication between server and client is conducted the same as for I/O streams.

3

Data Transmission through Sockets

int port = 8000;DataInputStream in;DataOutputStream out;ServerSocket server;Socket socket;

server =new ServerSocket(port);socket=server.accept();in=new DataInputStream (socket.getInputStream());out=new DataOutStream (socket.getOutputStream());System.out.println(in.readDouble());out.writeDouble(aNumber);

int port = 8000;String host="localhost"DataInputStream in;DataOutputStream out;Socket socket;

socket=new Socket(host, port);in=new DataInputStream (socket.getInputStream());out=new DataOutputStream (socket.getOutputStream());out.writeDouble(aNumber);System.out.println(in.readDouble());

ClientServer

ConnectionRequest

I/OStreams

InputStream input = socket.getInputStream();

OutputStream output = socket.getOutputStream();

4

A Client/Server Example

• Problem: Write a client to send data to a server. The server receives the data, uses it to produce a result, and then sends the result back to the client. The client displays the re-sult on the console. In this example, the data sent from the client is the radius of a circle, and the result produced bythe server is the area of the circle.

radius

Server Client

compute area

area

5

A Client/Server Example, cont.

Server

radius

DataInputStream

socket.getInputStream

socket

Network

Client

radius

DataOutputStream

socket.getOutputStream

socket

(A)

Server

area

DataOutputStream

socket.getOutputStream

socket

Network

Client

area

DataOutputStream

socket.getOutputStream

socket

(B)

6

A Client/Server Example, cont.

radius

Server Client

compute area

area

7

Server.java

8

Client.java

9

Client.java

13장 . 네트워킹

10

ServerSocket Class

- Constructor

- Method

ServerSocket(int port) throws IOException)형식

Method Description

Socket accept() throws IOExceptionListens for a connection to be made to this socket and accepts it.

void close() throws IOException Closes this socket.

13장 . 네트워킹

11

Socket Class

- Constructor

Socket(String hostName, int port) throws UnknownHostException, IOExcep-tion

형식

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Method

Method DescriptionOutputStream getOutputStream( ) throws IOException

Returns an output stream for this socket.

void close( ) throws IOException Closes this socket.

InetAddress getInetAddress( ) Returns the address to which the socket is connected.

InetAddress getLocalAddress( ) Gets the local address to which the socket is bound.

int getPort( )Returns the remote port number to which this socket is connected.

int getLocalPort( )Returns the local port number to which this socket is bound.

InputStream getInputStream( ) throws IOEx-ception

Returns an input stream for this socket.

13장 . 네트워킹

13

TCP Socket

Network

Network

Client ClientServer Server

13장 . 네트워킹

14

ExcercisesServerSide.java

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import java.io.*;import java.net.*;class ServerSide { public static void main(String args[]) throws Exception { int port = Integer.parseInt(args[0]); int times = Integer.parseInt(args[1]); ServerSocket ss = new ServerSocket(port); int i = 1; while( i <= times) { Socket s = ss.accept(); OutputStream os = s.getOutputStream(); DataOutputStream dos = new DataOutputStream(os); for(int j = 1 ; j <= 10 ; j++) dos.writeInt(j); s.close(); ++i; } } }

13장 . 네트워킹

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ExcercisesClientSide.java

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import java.io.*;import java.net.*;public class ClientSide { public static void main(String args[]) throws Exception { String server = args[0]; int port = Integer.parseInt(args[1]); Socket c = new Socket(server, port); InputStream is = c.getInputStream(); DataInputStream dis = new DataInputStream(is); for(int i=1 ; i <= 10 ; i++) { int j = dis.readInt(); System.out.println (j); } c.close(); }}

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16

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17

SimpleServer.java

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import java.io.*;import java.net.*;public class SimpleServer {

public static void main(String[] arsg) {ServerSocket s=null;try { s = new ServerSocket(5432); }catch (IOException e) { e.printStackTrace(); }System.out.println("Server Running.. Waiting Connetion ..");while (true) {

try {Socket s1 = s.accept();OutputStream s1out = s1.getOutputStream();BufferedWriterbw =

new BufferedWriter( new OutputStreamWriter(s1out));

bw.write("Server Message\n");bw.close();s1.close();

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

}}

}

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SimpleServer.java

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import java.io.*;import java.net.*;public class SimpleClient {

public static void main(String[] args) {try {

Socket s1 = new Socket("127.0.0.1", 5432);InputStreamir = s1.getInputStream();

BufferedReaderbr = new BufferedReader(new InputStream-Reader(ir));

int a = 0;while((a = br.read())!= -1){

System.out.print((char)a);}ir.close();s1.close();

}catch (ConnectExceptionconnExc) {

System.err.println("Could not connect ro the server");}catch (IOException e) {}

}}

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Server Message