OSI and TCP/IP Layers in Java Networking: Understanding Sockets, UDP, TCP, and Datagrams | Slides Java Programming

Basic Networking in Java

CalinCur escu

Basic Networking in Java

Calin Curescu

12 pages

TDDC32 lecture 2, 2006

Basic Networking in Java

CalinCur escu

2of 12

TDDC32 lecture 2, 2006

OSI and TCP/IP Layers

•ISO (International Standards Organization) has created a

layered model, called the OSI (Open Systems Interconnect)

•TCP/IP (Transmission Control Protocol / Internet Protocol)

already developed

OSI Layer Description TCP/IP Comments

Application Application level protocol

Presentation Encoding, Formatting

Session Manages end-user comm.

HTTP, FTP

Transport Transparent user data, rel iability,

manages packets

TCP, UDP Source and destination

port numbers

Network Packets between source &

destination, routing

IP Source & destination

IP numbers

Data Link Data between nodes

Physical Bits on the medi um (cable)

Network

frames

Basic Networking in Java

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TDDC32 lecture 2, 2006

TCP & UDP

•TCP

– Connection based protocol

• Data flows

• i.e. IP Packets are ordered, FIFO

– Reliable

• IP Packets are retransmitted

– Congestion and flow control

•UDP

– Connectionless protocol

• Independent datagrams

– Basically adding source and destination port to IP packet

• May arrive in any order

– Unreliable

• Datagrams can be lost

Basic Networking in Java

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TDDC32 lecture 2, 2006

java.net package

•Sockets

– One endpoint of a two-way communication link between two

programs running on the network

– ServerSocket, Socket classes in java.net

•URL (Uniform Resource Locator)

– http://ida.liu.se:80/figure.jpg (protocol:resource)

– Connecting to resource

– Reading & writing (using input and output streams)

•Datagrams

– Needed for UDP communication

– TCP provides reliable flows, which are automatically

transformed to InputStream and OutputStream

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TDDC32 lecture 2, 2006

Sockets for TCP

1. On server side, a socket (ServerSocket) is bound to a port and

listens for incoming client connections

2. On client side, the server address and port is known; the client

creates a new socket (Socket) and tries to connect to server

3. If everything ok

• On server side the server accepts the connection and creates a

new socket (Socket) bound on a different port

• Server needs the initial socket to continue to listen

• On client side the connection attempt returns successfully

4. Client and server can communicate by using the InputStream and

OutputStream provided by Socket

• Think about a pipe between server and client

• A “pipe” is uniquely identified by [server address, server port,

client address, client port]

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TDDC32 lecture 2, 2006

Server Example

import java.net.*;

import java.io.*;

public class EchoServer {

public static void main(String[] args) throws IOE xception {

ServerSocket serverSocket = null;

try {

serverSocket = new ServerSocket(7);

} catch (IOException e) {

System.err.println("Could not listen on port: 7");

System.exit(1);

}

Socket clientSocket = null;

try {

clientSocket = serverSocket.accept();

} catch (IOException e) {

System.err.println("Accept failed.");

System.exit(1);

}

PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);

BufferedReader in = new BufferedReader(new InputStreamReader(

clientSocket.getInputStream()));

String inputLine;

while ((inputLine = in.readLine()) != null) {

out.println(inputLine);

}

out.close();

in.close();

clientSocket.close();

serverSocket.close();

}

//thread blocks until a client connects

//ports under 1024 are usually reserved by OS

Examples from “Java Tutorials”:

http://java.sun.com/docs/books/tutorial/networking/

Partial preview of the text

Download OSI and TCP/IP Layers in Java Networking: Understanding Sockets, UDP, TCP, and Datagrams and more Slides Java Programming in PDF only on Docsity!

Basic Networking in Java Calin Curescu

Basic Networking in Java

Calin Curescu

12 pages TDDC32 lecture 2, 2006

Basic Networking in Java Calin Curescu

2 of 12 TDDC32 lecture 2, 2006

OSI and TCP/IP Layers

• ISO (International Standards Organization) has created a

layered model, called the OSI (Open Systems Interconnect)

• TCP/IP (Transmission Control Protocol / Internet Protocol)

already developed

OSI Layer Description TCP/IP Comments

Application Application level protocol

Presentation Encoding, Formatting

Session Manages end-user comm.

HTTP, FTP

Transport Transparent user data, reliability,

manages packets

TCP, UDP Source and destination

port numbers

Network Packets between source &

destination, routing

IP Source & destination

IP numbers

Data Link Data between nodes

Physical Bits on the medium (cable)

Network

frames

Basic Networking in Java Calin Curescu

3 of 12 TDDC32 lecture 2, 2006

TCP & UDP

• TCP

– Connection based protocol

• Data flows

• i.e. IP Packets are ordered, FIFO

– Reliable

• IP Packets are retransmitted

– Congestion and flow control

• UDP

– Connectionless protocol

• Independent datagrams

– Basically adding source and destination port to IP packet

• May arrive in any order

– Unreliable

• Datagrams can be lost

Basic Networking in Java Calin Curescu

4 of 12 TDDC32 lecture 2, 2006

java.net package

• Sockets

– One endpoint of a two-way communication link between two

programs running on the network

– ServerSocket, Socket classes in java.net

• URL (Uniform Resource Locator)

– http://ida.liu.se:80/figure.jpg (protocol:resource)

– Connecting to resource

– Reading & writing (using input and output streams)

• Datagrams

– Needed for UDP communication

– TCP provides reliable flows, which are automatically

transformed to InputStream and OutputStream

Basic Networking in Java Calin Curescu

5 of 12 TDDC32 lecture 2, 2006

Sockets for TCP

1. On server side, a socket (ServerSocket) is bound to a port and

listens for incoming client connections

2. On client side, the server address and port is known; the client

creates a new socket (Socket) and tries to connect to server

3. If everything ok

• On server side the server accepts the connection and creates a

new socket (Socket) bound on a different port

• Server needs the initial socket to continue to listen

• On client side the connection attempt returns successfully

4. Client and server can communicate by using the InputStream and

OutputStream provided by Socket

• Think about a pipe between server and client

• A “pipe” is uniquely identified by [server address, server port,

client address, client port]

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Server Example

import java.net.; import java.io.; public class EchoServer { public static void main(String[] args) throws IOException { ServerSocket serverSocket = null; try { serverSocket = new ServerSocket(7); } catch (IOException e) { System.err.println("Could not listen on port: 7"); System.exit(1); } Socket clientSocket = null; try { clientSocket = serverSocket.accept(); } catch (IOException e) { System.err.println("Accept failed."); System.exit(1); } PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true); BufferedReader in = new BufferedReader(new InputStreamReader( clientSocket.getInputStream())); String inputLine; while ((inputLine = in.readLine()) != null) { out.println(inputLine); } out.close(); in.close(); clientSocket.close(); serverSocket.close(); } }

//thread blocks until a client connects

//ports under 1024 are usually reserved by OS

Examples from “Java Tutorials”:

http://java.sun.com/docs/books/tutorial/networking/

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Client Example

import java.io.*;

import java.net.*;

public class EchoClient {

public static void main(String[] args) throws IOException {

Socket echoSocket = null;

PrintWriter out = null;

BufferedReader in = null;

try {

echoSocket = new Socket("dalix.ida.liu.se", 7);

out = new PrintWriter(echoSocket.getOutputStream(), true);

in = new BufferedReader(new InputStreamReader(echoSocket.getInputStream()));

} catch (UnknownHostException e) {

System.err.println("Unknown host: dalix.ida.liu.se ");

System.exit(1);

} catch (IOException e) {

System.err.println("IOException connecting to: dalix.ida.liu.se ");

System.exit(1);

BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));

String userInput;

while ((userInput = stdIn.readLine()) != null) {

out.println(userInput);

System.out.println("echo: " + in.readLine());

out.close();

in.close();

stdIn.close();

echoSocket.close();

//takes an available free local port //server’s address and port

//automatically tries to resolve

hostname to IP address (using a DNS)

//automatically tries connect to server

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Multiple clients

while (true) {

accept a connection ;

//returning a new socket

create a thread to deal with the client ;

//i.e. that takes as an argument the new created socket

• On the server side:

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Datagram Server

import java.io.*;

import java.net.*;

import java.util.*;

public class EchoDatagramServer {

public static void main(String[] args) throws IOException {

protected DatagramSocket socket = new DatagramSocket(7777);

while (true) {

try {

byte[] buf = new byte[256];

//receive request

DatagramPacket packet = new DatagramPacket(buf, buf.length);

socket.receive(packet);

//send the response to the client at "address" and "port"

InetAddress address = packet.getAddress();

int port = packet.getPort();

packet = new DatagramPacket(buf, buf.length, address, port);

socket.send(packet);

catch (IOException e) {

e.printStackTrace();

socket.close();

Basic Networking in Java Calin Curescu

10 of 12 TDDC32 lecture 2, 2006

Datagram Client

import java.io.; import java.net.; public class EchoDatagramClient { public static void main(String[] args) throws IOException { if (args.length != 1) { System.out.println("Usage: java DatagramClient "); System.exit(1); } //get a datagram socket DatagramSocket socket = new DatagramSocket(); String userInput; while ((userInput = stdIn.readLine()) != null) { //send request byte[] buf = userInput.getBytes(); InetAddress address = InetAddress.getByName(args[0]); DatagramPacket packet = new DatagramPacket(buf, buf.length, address, 7777); socket.send(packet); //get response packet = new DatagramPacket(buf, buf.length); socket.receive(packet); //display response String received = new String(packet.getData()); System.out.println("echo: " + received); } socket.close(); } }

OSI and TCP/IP Layers in Java Networking: Understanding Sockets, UDP, TCP, and Datagrams, Slides of Java Programming

Related documents

Partial preview of the text

Download OSI and TCP/IP Layers in Java Networking: Understanding Sockets, UDP, TCP, and Datagrams and more Slides Java Programming in PDF only on Docsity!

Basic Networking in Java

Calin Curescu

OSI and TCP/IP Layers

• ISO (International Standards Organization) has created a

layered model, called the OSI (Open Systems Interconnect)

• TCP/IP (Transmission Control Protocol / Internet Protocol)

already developed

OSI Layer Description TCP/IP Comments

Application Application level protocol

Presentation Encoding, Formatting

Session Manages end-user comm.

HTTP, FTP

Transport Transparent user data, reliability,

manages packets

TCP, UDP Source and destination

port numbers

Network Packets between source &

destination, routing

IP Source & destination

IP numbers

Data Link Data between nodes

Physical Bits on the medium (cable)

Network

frames

TCP & UDP

• TCP

– Connection based protocol

• Data flows

• i.e. IP Packets are ordered, FIFO

– Reliable

• IP Packets are retransmitted

– Congestion and flow control

• UDP

– Connectionless protocol

• Independent datagrams

– Basically adding source and destination port to IP packet

• May arrive in any order

– Unreliable

• Datagrams can be lost

java.net package

• Sockets

– One endpoint of a two-way communication link between two

programs running on the network

– ServerSocket, Socket classes in java.net

• URL (Uniform Resource Locator)

– http://ida.liu.se:80/figure.jpg (protocol:resource)

– Connecting to resource

– Reading & writing (using input and output streams)

• Datagrams

– Needed for UDP communication

– TCP provides reliable flows, which are automatically

transformed to InputStream and OutputStream

Sockets for TCP

1. On server side, a socket (ServerSocket) is bound to a port and

listens for incoming client connections

2. On client side, the server address and port is known; the client

creates a new socket (Socket) and tries to connect to server

3. If everything ok

• On server side the server accepts the connection and creates a

new socket (Socket) bound on a different port

• Server needs the initial socket to continue to listen

• On client side the connection attempt returns successfully

4. Client and server can communicate by using the InputStream and

OutputStream provided by Socket

• Think about a pipe between server and client

• A “pipe” is uniquely identified by [server address, server port,

client address, client port]

Server Example

//thread blocks until a client connects

//ports under 1024 are usually reserved by OS

Examples from “Java Tutorials”:

http://java.sun.com/docs/books/tutorial/networking/

Client Example

import java.io.*;

import java.net.*;

public class EchoClient {