Chapitre II M2 Internet et java H. Fauconnier 1-1 M2-Internet Java

Chapitre II

M2Internet et java

H. Fauconnier 1-1M2-Internet Java

Sommaire

Rappels java Entrées-sorties Thread

Rappels tcp-udp Socket tcp et SocketServer Socket udp compléments

H. Fauconnier M2-Internet Java 2

Entrées-sorties java

Streams Output streams Input streams Filter streams Readers et writer

(non blocking I/O)


OuputStream

public abstract class OutputStream public abstract void write(int b) throws IOException public void write(byte[] data) throws IOException Public void write(byte[] data, int offset, int length)

throws IOException public void flush( ) throws IOException public void close( ) throws IOException


http://download.oracle.com/javase/6/docs/api/java/io/OutputStream.html

InputStream

public abstract class InputStream

public abstract int read( ) throws IOException public int read(byte[] input) throws IOException public int read(byte[] input, int offset, int length) throws

IOException public long skip(long n) throws IOException public int available( ) throws IOException public void close( ) throws IOException public void mark(int readAheadLimit) public void reset( ) throws IOException public boolean markSupported( )


http://download.oracle.com/javase/6/docs/api/java/io/InputStream.html

Lecture:

int bytesRead=0;int bytesToRead=1024;byte[] input = new byte[bytesToRead];while (bytesRead < bytesToRead) { int result = in.read(input, bytesRead,

bytesToRead - bytesRead); if (result == -1) break; bytesRead += result;}


Filtres

Chainage des filtres:DataOutputStream dout = new

DataOutputStream(new BufferedOutputStream(new FileOutputStream ("data.txt")));


Filtres

Streams avec buffer BufferedInputStream BufferedOutputStream

PrintStream (System.out) PushbackInputStream Streams de données (lire et écrire des données java en

binaire) le codage est celui de java DataInputStream DataOutputStream

Streams avec compression Streams avec digest Streams cryptées


http://java.sun.com/javase/6/docs/api/java/io/BufferedInputStream.html

http://java.sun.com/javase/6/docs/api/java/io/BufferedOutputStream.html

http://java.sun.com/javase/6/docs/api/api/java/io/PrintStream.html

http://java.sun.com/javase/6/docs/api/java/io/PushbackInputStream.html

http://java.sun.com/javase/6/docs/api/java/io/DataInputStream.html

http://java.sun.com/javase/6/docs/api//java/io/DataOutputStream.html

Attention

Une méthode comme println est dépendante de la plate-forme: Le séparateur de ligne est soit \n, soit \r,

soit \r\n Le codage par défaut des caractères dépend

de la plate-forme PrintStream capte les exceptions


Compression

public class DeflaterOutputStream extends FilterOutputStreampublic class InflaterInputStream extends FilterInputStreampublic class GZIPOutputStream extends DeflaterOutputStreampublic class GZIPInputStream extends InflaterInputStreampublic class ZipOutputStream extends DeflaterOutputStreampublic class ZipInputStream extends InflaterInputStream


http://java.sun.com/javase/6/docs/api//java/util/zip/DeflaterOutputStream.html

http://java.sun.com/javase/6/docs/api/java/util/zip/DeflaterInputStream.html

http://java.sun.com/javase/6/docs/api/java/util/zip/GZIPOutputStream.html

http://java.sun.com/javase/6/docs/api/java/util/zip/GZIPInputStream.html

http://java.sun.com/javase/6/docs/api/java/util/zip/ZipOutputStream.html

http://java.sun.com/javase/6/docs/api/java/util/zip/ZipInputStream.html

décompresser une archive:

FileInputStream fin = new FileInputStream("shareware.zip");ZipInputStream zin = new ZipInputStream(fin);ZipEntry ze = null;int b = 0;while ((ze = zin.getNextEntry( )) != null) { FileOutputStream fout = new FileOutputStream(ze.getName( )); while ((b = zin.read( )) != -1) fout.write(b); zin.closeEntry( ); fout.flush( ); fout.close( );}zin.close( );


Décompresser un fichier

FileInputStream fin = new FileInputStream("allnames.gz");

GZIPInputStream gzin = new GZIPInputStream(fin);FileOutputStream fout = new

FileOutputStream("allnames");int b = 0;while ((b = gzin.read( )) != -1) fout.write(b);gzin.close( );out.flush( );out.close( );


digest

public class DigestOutputStream extends FilterOutputStream

public class DigestInputStream extends FilterInputStream


http://download.oracle.com/javase/6/docs/api/java/security/DigestOutputStream.html

http://download.oracle.com/javase/6/docs/api/java/security/DigestInputStream.html

Digest exemple:

MessageDigest sha = MessageDigest.getInstance("SHA");DigestOutputStream dout = new DigestOutputStream(out, sha);byte[] buffer = new byte[128];while (true) { int bytesRead = in.read(buffer); if (bytesRead < 0) break; dout.write(buffer, 0, bytesRead);}dout.flush( );dout.close( );byte[] result = dout.getMessageDigest( ).digest( );


Cryptage décryptage

public CipherInputStream(InputStream in, Cipher c)

public CipherOutputStream(OutputStream out, Cipher c)

Exemplebyte[] desKeyData = "Monmotdepasse".getBytes( );DESKeySpec desKeySpec = new DESKeySpec(desKeyData);SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");SecretKey desKey = keyFactory.generateSecret(desKeySpec);Cipher des = Cipher.getInstance("DES");des.init(Cipher.DECRYPT_MODE, desKey);CipherInputStream cin = new CipherInputStream(fin, des);


http://download.oracle.com/javase/6/docs/api/javax/crypto/CipherInputStream.html

http://download.oracle.com/javase/6/docs/api/api/javax/crypto/Cipher.html

http://download.oracle.com/javase/6/docs/api/javax/crypto/CipherOutputStream.html

http://download.oracle.com/javase/6/docs/api/api/javax/crypto/Cipher.html

Exemple

String infile = "secrets.txt";

String outfile = "secrets.des";String password = "Un mot de passe"; try { FileInputStream fin = new FileInputStream(infile); FileOutputStream fout = new FileOutputStream(outfile); // register the provider that implements the algorithm Provider sunJce = new com.sun.crypto.provider.SunJCE( ); Security.addProvider(sunJce); char[] pbeKeyData = password.toCharArray( ); PBEKeySpec pbeKeySpec = new PBEKeySpec(pbeKeyData); SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithMD5AndDES"); SecretKey pbeKey = keyFactory.generateSecret(pbeKeySpec);


Exemple suite

// use Data Encryption Standard Cipher pbe = Cipher.getInstance("PBEWithMD5AndDES"); pbe.init(Cipher.ENCRYPT_MODE, pbeKey); CipherOutputStream cout = new CipherOutputStream(fout, pbe); byte[] input = new byte[64]; while (true) { int bytesRead = fin.read(input); if (bytesRead == -1) break; cout.write(input, 0, bytesRead); } cout.flush( ); cout.close( ); fin.close( );}catch (Exception ex) { System.err.println(ex);}


Readers et Writers

Hiérarchie de classe pour les caractères (avec encodage) au lieu d’octets.

Writer et Reader classes abstraites OutputStreamWriter InputStreamReader Filtres

• BufferedReader, BufferedWriter• LineNumberReader• PushbackReader• PrintReader


http://download.oracle.com/javase/6/docs/api/java/io/Writer.html

http://download.oracle.com/javase/6/docs/api/java/io/Reader.html

http://download.oracle.com/javase/6/docs/api/java/io/OutputStreamWriter.html

http://download.oracle.com/javase/6/docs/api/java/io/InputStreamReader.html

Reader et Writer

OutputStreamWriter reçoit des caractères, les convertit en octets suivant un certain codage

public OutputStreamWriter(OutputStream out, String encoding) throws UnsupportedEncodingException

public OutputStreamWriter(OutputStream out)

Exemple: OutputStreamWriter w = new

OutputStreamWriter( new FileOutputStream("russe.txt",

"Cp1251"));


Reader et Writer

InputStreamReader lit des octets et les convertit suivant un certain codage public InputStreamReader(InputStream in) public InputStreamReader(InputStream in, String encoding)

throws UnsupportedEncodingException public static String getMacCyrillicString(InputStream in) throws IOException { InputStreamReader r = new InputStreamReader(in, "MacCyrillic"); StringBuffer sb = new StringBuffer( ); int c; while ((c = r.read( )) != -1) sb.append((char) c); r.close( ); return sb.toString( ); }


Filtres

BufferedReader BufferedWriter LineNumberReader PushbackReader PrintWriter


Threads


Threads

threads: plusieurs activités qui coexistent et partagent des données exemples:

• pendant un chargement long faire autre chose• coopérer• processus versus threads

problème de l'accès aux ressources partagées

• verrous• moniteur• synchronisation


Principes de base

extension de la classe Thread méthode run est le code qui sera exécuté. la création d'un objet dont la superclasse

est Thread crée la thread (mais ne la démarre pas)

la méthode start démarre la thread (et retourne immédiatement)

la méthode join permet d'attendre la fin de la thread

les exécutions des threads sont asynchrones et concurrentes


http://download.oracle.com/javase/6/docs/api/java/lang/Thread.html

Exemple

class ThreadAffiche extends Thread{ private String mot; private int delay; public ThreadAffiche(String w,int duree){ mot=w; delay=duree; } public void run(){ try{ for(;;){ System.out.println(mot); Thread.sleep(delay); } }catch(InterruptedException e){ } }}


Suite

public static void main(String[] args) { new ThreadAffiche("PING", 10).start(); new ThreadAffiche("PONG", 30).start(); new ThreadAffiche("Splash!",60).start(); }


Alternative: Runnable

Une autre solution: créer une classe qui implémente l'interface

Runnable (cette interface contient la méthode run)

créer une Thread à partir du constructeur Thread avec un Runnable comme argument.


http://download.oracle.com/javase/6/docs/api/java/lang/Runnable.html

Exemple

class RunnableAffiche implements Runnable{ private String mot; private int delay; public RunnableAffiche(String w,int duree){ mot=w; delay=duree; } public void run(){ try{ for(;;){ System.out.println(mot); Thread.sleep(delay); } }catch(InterruptedException e){ } }}


Suite

public static void main(String[] args) {

Runnable ping=new RunnableAffiche("PING", 10); Runnable pong=new RunnableAffiche("PONG", 50); new Thread(ping).start(); new Thread(pong).start();}


Synchronisation

les threads s'exécutent concurremment et peuvent accéder concurremment à des objets: il faut contrôler l'accès:

– thread un lit une variable (R1) puis modifie cette variable (W1)

– thread deux lit la même variable (R2) puis la modifie (W2)

– R1-R2-W2-W1

– R1-W1-R2-W2 résultat différent!


Exemple

class X{ int val; } class Concur extends Thread{ X x; int i; String nom; public Concur(String st, X x){ nom=st; this.x=x; } public void run(){ i=x.val; System.out.println("thread:"+nom+" valeur x="+i); try{ Thread.sleep(10); }catch(Exception e){} x.val=i+1; System.out.println("thread:"+nom+" valeur x="+x.val); } }


Suite

public static void main(String[] args) { X x=new X(); Thread un=new Concur("un",x); Thread deux=new Concur("deux",x); un.start(); deux.start(); try{ un.join(); deux.join(); }catch (InterruptedException e){} System.out.println("X="+x.val); }donnera (par exemple) thread:un valeur x=0 thread:deux valeur x=0 thread:un valeur x=1 thread:deux valeur x=1 X=1


Deuxième exemple

class Y{ int val=0; public int increment(){ int tmp=val; tmp++; try{ Thread.currentThread().sleep(100); }catch(Exception e){} val=tmp; return(tmp); } int getVal(){return val;}}class Concur1 extends Thread{ Y y; String nom; public Concur1(String st, Y y){ nom=st; this.y=y; } public void run(){ System.out.println("thread:"+nom+" valeur="+y.increment()); }}


Suite

public static void main(String[] args) { Y y=new Y(); Thread un=new Concur1("un",y); Thread deux=new Concur1("deux",y); un.start(); deux.start(); try{ un.join(); deux.join(); }catch (InterruptedException e){} System.out.println("Y="+y.getVal()); }----------- thread:un valeur=1 thread:deux valeur=1 Y=1


Verrous

à chaque objet est associé un verrou synchronized(expr) {instructions}

• expr doit s'évaluer comme une référence à un objet

• verrou sur cet objet pour la durée de l'exécution de instructions

déclarer les méthodes comme synchronized: la thread obtient le verrou et le relâche quand la méthode se termine


synchronised(x)

class Concur extends Thread{ X x; int i; String nom; public Concur(String st, X x){ nom=st; this.x=x; } public void run(){ synchronized(x){ i=x.val; System.out.println("thread:"+nom+" valeur x="+i); try{ Thread.sleep(10); }catch(Exception e){} x.val=i+1; System.out.println("thread:"+nom+" valeur x="+x.val); } }}


Méthode synchronisée

class Y{ int val=0; public synchronized int increment(){ int tmp=val; tmp++; try{ Thread.currentThread().sleep(100); }catch(Exception e){} val=tmp; return(tmp); } int getVal(){return val;}}------------ thread:un valeur=1 thread:deux valeur=2 Y=2


Mais…

la synchronisation par des verrous peut entraîner un blocage: la thread un (XA) pose un verrou sur l'objet

A et (YB) demande un verrou sur l'objet B la thread deux (XB) pose un verrou sur

l'objet B et (YA) demande un verrou sur l'objet A

si XA –XB : ni YA ni YB ne peuvent êter satisfaites -> blocage

(pour une méthode synchronisée, le verrou concerne l'objet globalement et pas seulement la méthode)


Exemple

class Dead{ Dead partenaire; String nom; public Dead(String st){ nom=st; } public synchronized void f(){ try{ Thread.currentThread().sleep(100); }catch(Exception e){} System.out.println(Thread.currentThread().getName()+ " de "+ nom+".f() invoque "+ partenaire.nom+".g()"); partenaire.g(); } public synchronized void g(){ System.out.println(Thread.currentThread().getName()+ " de "+ nom+".g()"); } public void setPartenaire(Dead d){ partenaire=d; }}


Exemple (suite)

final Dead un=new Dead("un"); final Dead deux= new Dead("deux"); un.setPartenaire(deux); deux.setPartenaire(un); new Thread(new Runnable(){public void run(){un.f();} },"T1").start(); new Thread(new Runnable(){public void run(){deux.f();} },"T2").start();------------

T1 de un.f() invoque deux.g() T2 de deux.f() invoque un.g()


Synchronisation…

wait, notifyAll notify attendre une condition / notifier le

changement de condition:synchronized void fairesurcondition(){

while(!condition)wait();faire ce qu'il faut qaund la condition est vraie}

-----------------synchronized void changercondition(){

… changer quelque chose concernant la conditionnotifyAll(); // ou notify()

}


Exemple (file: rappel Cellule)

public class Cellule<E>{ private Cellule<E> suivant; private E element; public Cellule(E val) { this.element=val; } public Cellule(E val, Cellule suivant){ this.element=val; this.suivant=suivant; } public E getElement(){ return element; } public void setElement(E v){ element=v; } public Cellule<E> getSuivant(){ return suivant; } public void setSuivant(Cellule<E> s){ this.suivant=s; }


Files synchronisées

class File<E>{ protected Cellule<E> tete, queue; private int taille=0;

public synchronized void enfiler(E item){ Cellule<E> c=new Cellule<E>(item); if (queue==null) tete=c; else{ queue.setSuivant(c); } c.setSuivant(null); queue = c; notifyAll(); }


File (suite)

public synchronized E defiler() throws InterruptedException{ while (tete == null) wait(); Cellule<E> tmp=tete; tete=tete.getSuivant(); if (tete == null) queue=null; return tmp.getElement(); }


Réseau et Java

Rappels Tcp-udp


I) Introduction

Les couches


Couche Internet

Datagramme IPv4


Couche transport

TCP Mode connecté, flot bidirectionnel, sûr,

contrôle de la congestion Téléphone

UDP Mode non connecté, messages, sans

garantie, déséquencement Poste


Adresses internet

Adresse IP: adresse réseau + site sur le réseau

Exemple:


Classe d’adresses Internet

Classe Bits départ Début Fin Notation CIDR Masque ss-réseau

Classe A 0 0.0.0.0 127.255.255.255 /8 255.0.0.0

Classe B 10 128.0.0.0 191.255.255.255 /16 255.255.0.0

Classe C 110 192.0.0.0 223.255.255.255 /24 255.255.255.0

Classe D (mcast) 1110 224.0.0.0 239.255.255.255 /4 non défini

Classe E (réservée) 1111 240.0.0.0 255.255.255.255 /4 non défini


Classe Nombre de réseaux possibles Nombre d'ordinateurs maxi sur chacunA 126 16777214B 16384 65534C 2097152 254

Connexion

Adresse IP +port Ports réservés Ports libres


Quelques ports


Protocol Port Protocol

echo 7 TCP/UDP

discard 9 TCP/UDP

daytime 13 TCP/UDP

FTP data 20 TCP

FTP 21 TCP

SSH 22 TCP

telnet 23 TCP

smtp 25 TCP

time 37 TCP/UDP

Protocol Port Protocol

whois 43 TCP

finger 79 TCP

HTTP 80 TCP

POP3 110 TCP

NNTP 119 TCP

IMAP 143 TCP

RMI Registry109

9TCP

Proxys


Comment travailler avec un proxy? Régler le navigateur… les applets du

navigateur utilisent ces réglages Pour une application java il faut préciser les

propriétés: socksProxyHo socksProxyPor (SOCKS proxy server), http.proxySet, http.proxyHost, http.proxyPort, https.proxySet, https.proxyHost, https.proxyPort, ftpProxySet, ftpProxyHost, ftpProxyPort, gopherProxySet, gopherProxyHost, gopherProxyPort (pour les autres protocoles).

Pour cela: java -DsocksProxyHost= socks.cloud9.net -

DsocksProxyPort= 1080 MyClass


Client-serveur


Classes

java.net.InetAddress (implements java.io.Serializable) java.net.Inet4Address

java.net.Inet6Address

java.net.DatagramPacket java.net.DatagramSocket

java.net.MulticastSocket

java.net.ServerSocket javax.net.ssl.SSLServerSocket

java.net.Socket javax.net.ssl.SSLSocket

java.net.SocketAddress (implements java.io.Serializable) java.net.InetSocketAddress


http://java.sun.com/j2se/1.5.0/docs/api/java/net/InetAddress.html

http://java.sun.com/j2se/1.5.0/docs/api/java/io/Serializable.html

http://java.sun.com/j2se/1.5.0/docs/api/java/net/Inet4Address.html

http://java.sun.com/j2se/1.5.0/docs/api/java/net/Inet6Address.html

http://java.sun.com/j2se/1.5.0/docs/api/java/net/DatagramPacket.html

http://java.sun.com/j2se/1.5.0/docs/api/java/net/DatagramSocket.html

http://java.sun.com/j2se/1.5.0/docs/api/java/net/MulticastSocket.html

http://java.sun.com/j2se/1.5.0/docs/api/java/net/ServerSocket.html

http://java.sun.com/j2se/1.5.0/docs/api/javax/net/ssl/SSLServerSocket.html

http://java.sun.com/j2se/1.5.0/docs/api/java/net/Socket.html

http://java.sun.com/j2se/1.5.0/docs/api/javax/net/ssl/SSLSocket.html

http://java.sun.com/j2se/1.5.0/docs/api/java/net/SocketAddress.html

http://java.sun.com/j2se/1.5.0/docs/api/java/io/Serializable.html

http://java.sun.com/j2se/1.5.0/docs/api/java/net/InetSocketAddress.html

Classes

Channel: java.nio.channels.spi.AbstractInterruptibleChannel

(implements java.nio.channels.Channel, java.nio.channels.InterruptibleChannel) java.nio.channels.SelectableChannel (implements

java.nio.channels.Channel) • java.nio.channels.spi.AbstractSelectableChannel

– java.nio.channels.DatagramChannel (implements java.nio.channels.ByteChannel, java.nio.channels.GatheringByteChannel, java.nio.channels.ScatteringByteChannel)

– java.nio.channels.ServerSocketChannel – java.nio.channels.SocketChannel (implements java.nio.channels.ByteChannel,

java.nio.channels.GatheringByteChannel, java.nio.channels.ScatteringByteChannel)


http://java.sun.com/j2se/1.5.0/docs/api/java/nio/channels/spi/AbstractInterruptibleChannel.html

II) Adresses internet

Classe InetAddress: Ontenir une InetAddress:

En utilisant le DNS• public static InetAddress getByName(String

hostName) throws UnknownHostException • public static InetAddress[] getAllByName(String

hostName) throws UnknownHostException • public static InetAddress getLocalHost( ) throws

UnknownHostException Sans DNS

• public static InetAddress getByAddress(byte[] address) throws UnknownHostException

• public static InetAddress getByAddress(String hostName, byte[] address) throws

UnknownHostException


Exemples

import java.net.*; /...public static void main (String[] args){

try { InetAddress adresse =

InetAddress.getByName("liafa.jussieu.fr"); System.out.println(adresse); } catch (UnknownHostException ex) { System.out.println("liafa.jussieu.fr ??"); }

}


Exemples

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

InetAddress ad =

InetAddress.getByName("192.227.93.1"); System.out.println(ad); } catch (UnknownHostException ex) { System.out.println("192.227.93.1 ??"); }

}


Toutes les adresses…

public static void AllAdresses(String st) { try { InetAddress[] addresses = InetAddress.getAllByName(st); for (int i = 0; i < addresses.length; i++) { System.out.println(addresses[i]); } } catch (UnknownHostException ex) { System.out.println(st+"est inconnu"); } }


Mon adresse

public static String MonAdresse() { try { InetAddress moi = InetAddress.getLocalHost(); return( moi.getHostAddress()); } catch (UnknownHostException ex) { return("Mon adresse est inconnue"); } }


InetAddress méthodes…

public String getHostName( )public byte[] getAddress( )public String getHostAddress( ) Exemple:public static void main (String[] args) { try {

InetAddress ia= InetAddress.getByName("192.168.22.1"); System.out.println(ia.getHostName( ));

} catch (Exception ex) { System.err.println(ex); }

}


Divers…

public boolean isAnyLocalAddress( ) « wildcard »?

public boolean isLoopbackAddress( ) public boolean isMulticastAddress( ) Java 1.5

public boolean isReachable(int timeout) throws IOException

public boolean isReachable(NetworkInterface interface, int ttl, int timeout) throws IOException

IPV4 et IPV6:• public final class Inet4Address extends InetAddress • public final class Inet6Address extends InetAddress


NetworkInterface

Exemple:try {

NetworkInterface ni = NetworkInterface.getByName("eth0"); if (ni == null) {

System.err.println(" pas de:eth0" ); }

} catch (SocketException ex) { }


Exemple

public static String lookup(String host) { InetAddress node; // récupérer l'adresse par getByName try { node = InetAddress.getByName(host); } catch (UnknownHostException ex) { return "hôte inconnu " + host; } if (isHostname(host)) { return node.getHostAddress(); } else { return node.getHostName(); } }


sockets (client)

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M2-Internet Java

M2-Internet Java 68

Socket programming

Socket API introduced in BSD4.1

UNIX, 1981 explicitly created, used,

released by apps client/server paradigm two types of transport

service via socket API: UDP TCP

A application-created, OS-controlled interface (a

“door”) into whichapplication process can both

send and receive messages to/from

another application process

socket

Goal: learn how to build client/server application that communicate using sockets

H. Fauconnier

Socket programming basics

Server must be running before client can send anything to it.

Server must have a socket (door) through which it receives and sends segments

Similarly client needs a socket

Socket is locally identified with a port number Analogous to the apt

# in a building Client needs to know

server IP address and socket port number.

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Socket-programming using TCP

TCP service: reliable transfer of bytes from one process to another

process

TCP withbuffers,

variables

socket

controlled byapplication

developer

controlled byoperating

system

host orserver

process

TCP withbuffers,

variables

socket

controlled byapplicationdeveloper

controlled byoperatingsystem

host orserver

internet

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Socket programming with TCPClient must contact server server process must first

be running server must have created

socket (door) that welcomes client’s contact

Client contacts server by: creating client-local TCP

socket specifying IP address, port

number of server process When client creates

socket: client TCP establishes connection to server TCP

When contacted by client, server TCP creates new socket for server process to communicate with client allows server to talk

with multiple clients source port numbers

used to distinguish clients (more in Chap 3)

TCP provides reliable, in-order transfer of bytes (“pipe”) between client and server

application viewpoint

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Client/server socket interaction: TCP

wait for incomingconnection requestconnectionSocket =welcomeSocket.accept()

create socket,port=x, forincoming request:welcomeSocket =

ServerSocket()

create socket,connect to hostid, port=xclientSocket =

Socket()

closeconnectionSocket

read reply fromclientSocket

closeclientSocket

Server (running on hostid) Client

send request usingclientSocketread request from

connectionSocket

write reply toconnectionSocket

TCP connection setup

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tToS

erve

r

to network from network

inFr

omS

erve

r

inFr

omU

ser

keyboard monitor

Process

clientSocket

inputstream

inputstream

outputstream

TCPsocket

Clientprocess

client TCP socket

Stream jargon

A stream is a sequence of characters that flow into or out of a process.

An input stream is attached to some input source for the process, e.g., keyboard or socket.

An output stream is attached to an output source, e.g., monitor or socket.

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Socket programming with TCP

Example client-server app:

1) client reads line from standard input (inFromUser stream) , sends to server via socket (outToServer stream)

2) server reads line from socket3) server converts line to

uppercase, sends back to client

4) client reads, prints modified line from socket (inFromServer stream)

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Example: Java client (TCP)

import java.io.*; import java.net.*; class TCPClient {

public static void main(String argv[]) throws Exception { String sentence; String modifiedSentence;

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

Socket clientSocket = new Socket("hostname", 6789);

DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());

Createinput stream

Create client socket,

connect to server

Createoutput stream

attached to socket

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M2-Internet Java 76

Example: Java client (TCP), cont.

BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));

sentence = inFromUser.readLine();

outToServer.writeBytes(sentence + '\n');

modifiedSentence = inFromServer.readLine();

System.out.println("FROM SERVER: " + modifiedSentence);

clientSocket.close(); } }

Createinput stream

attached to socket

Send lineto server

Read linefrom server

H. Fauconnier

M2-Internet Java 77

Example: Java server (TCP)import java.io.*; import java.net.*;

class TCPServer {

public static void main(String argv[]) throws Exception { String clientSentence; String capitalizedSentence;

ServerSocket welcomeSocket = new ServerSocket(6789); while(true) { Socket connectionSocket = welcomeSocket.accept();

BufferedReader inFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));

Createwelcoming socket

at port 6789

Wait, on welcomingsocket for contact

by client

Create inputstream, attached

to socket

H. Fauconnier

M2-Internet Java 78

Example: Java server (TCP), cont

DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());

clientSentence = inFromClient.readLine();

capitalizedSentence = clientSentence.toUpperCase() + '\n';

outToClient.writeBytes(capitalizedSentence); } } }

Read in linefrom socket

Create outputstream, attached

to socket

Write out lineto socket

End of while loop,loop back and wait foranother client connection

H. Fauconnier

TCP observations & questions

Server has two types of sockets: ServerSocket and Socket

When client knocks on serverSocket’s “door,” server creates connectionSocket and completes TCP conx.

Dest IP and port are not explicitly attached to segment.

Can multiple clients use the server?


Généralités

Une connexion: (IP adresse+port, IP adresse +port) On peut lire et écrire sur la socket

Serveur: Associer une socket à une adresse connue (IP+port) Ecoute sur la socket Quand une connexion arrive accept : une nouvelle socket est

créée • Rendre le service envoyer/recevoir

– (en général dans une thread)• Continuer à écouter

Client: Crée une socket Demande connexion sur adresse +port du serveur Connexion Envoyer/recevoir Fin de la connexion


Socket en Java

Serveur Classe ServerSocket

• (bind (mais en général par constructeur)• listen)• Accept• getInputStream, getOutputStream• close

Client Classe Socket

• (bind)• connect (mais en général par constructeur)• getInputStream, getOutputStream• close


Attention!

L’accès aux ports est souvent restreint Des firewall peuvent empêcher les

connexions Il faut être root pour utiliser des ports

réservés…


Côté client

Création: public Socket(InetAddress address, int port) throws

IOException Crée une socket + une connexion avec IP adresse et

port En fait:

• Création d’une socket locale attachée à un port + une adresse locale

• Etablissement de la connexion• IOException en cas d’échec


Exemple

public static void regarderPortBas(String host) { for (int i = 1; i < 1024; i++) { try { Socket s = new Socket(host, i); System.out.println("Il y a un serveur sur "

+ i + " de "+ host); } catch (UnknownHostException ex) { System.err.println(ex); break; } catch (IOException ex) { // exception s'il n'y a pas de serveur } } }


Attention

Cet exemple peut ne pas bien fonctionner… Pour des raisons de sécurité la tentative de

connexion peut être bloquante


Autres constructeurs

try { InetAddress inward =

InetAddress.getByName("router"); Socket socket = new Socket("mail", 25, inward, 0);}catch (UnknownHostException ex) { System.err.println(ex);} Connexion à partir de l'interface réseau et du port

spécifié, ‘0’ signifie n’importe quel port


Avec un proxy

SocketAddress proxyAddress = new InetSocketAddress("myproxy.example.com", 1080);

Proxy proxy = new Proxy(Proxy.Type.SOCKS, proxyAddress)

Socket s = new Socket(proxy);SocketAddress remote = new

InetSocketAddress("login.ibiblio.org", 25);s.connect(remote);


Obtenir des infos…

public InetAddress getInetAddress( ) public int getPort( ) public InetAddress getLocalAddress( ) public int getLocalPort( )


Exemple

public static void socketInfo(String ... args) { for (int i = 0; i < args.length; i++) { try { Socket theSocket = new Socket(args[i], 80); System.out.println("Connecté sur " +

theSocket.getInetAddress() + " port " + theSocket.getPort() + " depuis port " + theSocket.getLocalPort() + " de " + theSocket.getLocalAddress()); } catch (UnknownHostException ex) { System.err.println("Hôte inconnu " + args[i]); } catch (SocketException ex) { System.err.println("Connection impossible " + args[i]); } catch (IOException ex) { System.err.println(ex); } } }


Communiquer…

public InputStream getInputStream( ) throws IOException

public OutputStream getOutputStream( ) throws IOException


Exemple: dayTime

public static void time(String ... hlist) { for (int i=0;i<hlist.length;i++){ try { Socket theSocket = new Socket(hlist[i], 13); InputStream timeStream = theSocket.getInputStream(); StringBuffer time = new StringBuffer(); int c; while ((c = timeStream.read()) != -1) time.append((char) c); String timeString = time.toString().trim(); System.out.println("Il est " + timeString + " à " +

hlist[i]); } catch (UnknownHostException ex) { System.err.println(ex); } catch (IOException ex) { System.err.println(ex); } } }


Exemple: echo

public static void echo(String hostname, int port) { PrintWriter out = null; BufferedReader networkIn = null; try { Socket theSocket = new Socket(hostname, port); networkIn = new BufferedReader( new InputStreamReader(theSocket.getInputStream())); BufferedReader userIn = new BufferedReader( new InputStreamReader(System.in)); out = new PrintWriter(theSocket.getOutputStream()); System.out.println("Client: Connecté au serveur d'echo "+ theSocket); while (true) { String theLine = userIn.readLine(); out.println(theLine); out.flush(); if (theLine.equals(".")){out.close(); break;} System.out.println(networkIn.readLine()); } } catch (IOException ex) {System.err.println(ex); } finally { try { if (networkIn != null) networkIn.close(); if (out != null) out.close(); } catch (IOException ex) {} } }

}


Echo suite

catch (IOException ex) { System.err.println(ex);} finally { try { if (networkIn != null) networkIn.close(); if (out != null) out.close(); } catch (IOException ex) {} }


Fermeture

public void close( ) throws IOException Fermeture de la socket:

Automatique si une des parties fait un close garbage collector (le réseau utilise des ressources systèmes

qui sont par définition partagées et limitées) (a priori à mettre dans une clause finally )


En plus

public boolean isClosed( ) public boolean isConnected( ) public boolean isBound( ) public void shutdownInput( ) throws

IOException public void shutdownOutput( )

throws IOException


Et aussi

TCP_NODELAY SO_TIMEOUT SO_LINGER SO_SNDBUF SO_RCVBUF SO_KEEPALIVE OOBINLINE SO_REUSEADDR


ServerSocket

H. Fauconnier 1-98

M2-Internet Java

Principe

1. Création d’un ServerSocket par constructeur

2. Association (bind) de la socket à une adresse et un port ((1) et (2) peuvent être simultanés)

3. Écoute et connexion par accept1. Communication getInputStream et

getOutputStream2. close (par le client ou le serveur ou les

deux)4. Aller en (2)

(en général 3 est dans une thread)


Constructeurs

public ServerSocket(int port) throws BindException, IOException

public ServerSocket(int port, int queueLength) throws BindException, IOException

public ServerSocket(int port, int queueLength, InetAddress bindAddress) throws

IOException Ces constructeurs associent un port et une

adresse au ServerSocket l’usage du port est exclusif et si le port est déjà occupé une exception est lancée public ServerSocket( ) throws IOException


Exemple

public static void portsLibres() { for (int port = 1; port <= 65535; port++) { try { // exception si le port est utilisé ServerSocket server = new

ServerSocket(port); } catch (IOException ex) { System.out.println("serveur sur port"

+ port ); } } }


Remarques

port 0: choisi par le système on peut donner une taille sur la file des

connexions en attente on peut choisir une adresse particulière

sur la machine locale En java >1.4 on peut faire un "bind"

explicite:• public void bind(SocketAddress endpoint)

throws IOException• public void bind(SocketAddress endpoint,

int queueLength) throws IOException


Exemple

public static void portQuelconque() { try { ServerSocket server = new ServerSocket(0); System.out.println("Le port obtenu est " + server.getLocalPort()); } catch (IOException ex) { System.err.println(ex); }}


Connexion accept()

crée et retourne une nouvelle socket pour la connexion associée (IP, port)(IP, port)


Exemple

ServerSocket server = new ServerSocket(5776);while (true) { Socket connection = server.accept( ); OutputStreamWriter out = new

OutputStreamWriter( connection.getOutputStream( ));

out.write("Connecté:" +connection+"\r\n"); connection.close( );}


Exemple plus complet

public final static int DEFAULT_PORT = 13;public static void dayTime(){ dayTime(DEFAULT_PORT); } public static void dayTime(int port) { if (port < 0 || port >= 65536) { System.out.println("Erreur port:"); return; } try { ServerSocket server = new ServerSocket(port); Socket connection = null;


Exemple suite

while (true) { try { connection = server.accept(); Writer out = new OutputStreamWriter(

connection.getOutputStream()); Date now = new Date(); out.write(now.toString() +"\r\n"); out.flush(); connection.close(); } catch (IOException ex) {} finally { try { if (connection != null) connection.close(); } catch (IOException ex) {} } } } catch (IOException ex) { System.err.println(ex); } }


Fermeture

public void close( ) throws IOException

Ferme le ServerSocket et toutes les connexions créées par accept sur la ServerSocket


Serveur echo

public static void serveurEcho(int port) { try { ServerSocket server = new ServerSocket(port,100); System.out.println("Serveur:"+server+" en écoute sur le port: " + server.getLocalPort()+" est lancé"); while (true) { Socket connection = server.accept(); System.out.println("Serveur connexion avec: " + connection); Thread echo=new EchoThread(connection); echo.start(); } catch (IOException ex) { System.out.println("le port" + port + " est occupé"); System.out.println("On suppose donc que le service estlancé"); } } }


serveur echo: EchoThread

class EchoThread extends Thread { BufferedReader in; PrintWriter out; Socket connection; public EchoThread(Socket connection) { try{ this.connection=connection; InputStream in=connection.getInputStream(); OutputStream out=connection.getOutputStream(); this.in = new BufferedReader(new

InputStreamReader(in)); this.out = new PrintWriter(out); } catch (IOException ex) { System.err.println(ex); } }


run

public void run() { try { while (true) { String st; st = in.readLine(); if (st.equals(".")) in.close(); out.close(); break; } System.out.println("Serveur a reçu:"+st+" de "+connection); out.println(st); out.flush(); } } catch (SocketException ex) { ex.printStackTrace(); } catch (IOException ex) { System.err.println(ex); } try { in.close(); out.close(); } catch (IOException ex) { ex.printStackTrace();} } }


Remarques

utilisation des threads pour traiter le service et éviter de faire attendre les clients

on peut aussi utiliser des entrées/sorties non bloquantes


Autres méthodes

public InetAddress getInetAddress( ) public int getLocalPort( )


Options

SO_TIMEOUT SO_REUSEADDR SO_RCVBUF public void setPerformancePreferences(int

connectionTime, int latency, int bandwidth


Socket UDP

H. Fauconnier 1-115

M2-Internet Java

UDP


M2-Internet Java 117

Socket programming with UDP

UDP: no “connection” between client and server

no handshaking sender explicitly attaches

IP address and port of destination to each segment

OS attaches IP address and port of sending socket to each segment

Server can extract IP address, port of sender from received segment

application viewpoint

UDP provides unreliable transfer of groups of bytes (“datagrams”)

between client and server

Note: the official terminology for a UDP packet is “datagram”. In this class, we instead use “UDP segment”.

H. Fauconnier

Running example

Client: User types line of text Client program sends line to server

Server: Server receives line of text Capitalizes all the letters Sends modified line to client

Client: Receives line of text Displays



Client/server socket interaction: UDP

Server (running on hostid)

closeclientSocket

read datagram fromclientSocket

create socket,

clientSocket = DatagramSocket()

Client

Create datagram with server IP andport=x; send datagram via clientSocket

create socket,port= x.serverSocket = DatagramSocket()

read datagram fromserverSocket

write reply toserverSocketspecifying client address,port number

H. Fauconnier


Example: Java client (UDP)

sendP

ack

et

to network from network

rece

iveP

ack

et

inF

rom

Use

r

keyboard monitor

Process

clientSocket

UDPpacket

inputstream

UDPpacket

UDPsocket

Output: sends packet (recallthat TCP sent “byte stream”)

Input: receives packet (recall thatTCP received “byte stream”)

Clientprocess

client UDP socket

H. Fauconnier


Example: Java client (UDP)

import java.io.*; import java.net.*; class UDPClient { public static void main(String args[]) throws Exception { BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in)); DatagramSocket clientSocket = new DatagramSocket(); InetAddress IPAddress = InetAddress.getByName("hostname"); byte[] sendData = new byte[1024]; byte[] receiveData = new byte[1024]; String sentence = inFromUser.readLine();

sendData = sentence.getBytes();

Createinput stream

Create client socket

Translate hostname to IP

address using DNS

H. Fauconnier


Example: Java client (UDP), cont.

DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 9876); clientSocket.send(sendPacket); DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length); clientSocket.receive(receivePacket); String modifiedSentence = new String(receivePacket.getData()); System.out.println("FROM SERVER:" + modifiedSentence); clientSocket.close(); }

}

Create datagram with data-to-send,

length, IP addr, port

Send datagramto server

Read datagramfrom server

H. Fauconnier


Example: Java server (UDP)

import java.io.*; import java.net.*; class UDPServer { public static void main(String args[]) throws Exception { DatagramSocket serverSocket = new DatagramSocket(9876); byte[] receiveData = new byte[1024]; byte[] sendData = new byte[1024]; while(true) { DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);

serverSocket.receive(receivePacket);

Createdatagram socket

at port 9876

Create space forreceived datagram

Receivedatagram

H. Fauconnier


Example: Java server (UDP), cont

String sentence = new String(receivePacket.getData()); InetAddress IPAddress = receivePacket.getAddress(); int port = receivePacket.getPort(); String capitalizedSentence = sentence.toUpperCase();

sendData = capitalizedSentence.getBytes(); DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, port); serverSocket.send(sendPacket); } }

}

Get IP addrport #, of

sender

Write out datagramto socket

End of while loop,loop back and wait foranother datagram

Create datagramto send to client

H. Fauconnier

UDP observations & questions Both client server use DatagramSocket Dest IP and port are explicitly attached to

segment. What would happen if change both clientSocket

and serverSocket to “mySocket”? Can the client send a segment to server without

knowing the server’s IP address and/or port number?

Can multiple clients use the server?


DatagramPacket

Un paquet contient au plus 65,507 bytes Pour construire les paquet

public DatagramPacket(byte[] buffer, int length) public DatagramPacket(byte[] buffer, int offset, int length)

Pour construire et envoyer public DatagramPacket(byte[] data, int length, InetAddress

destination, int port) public DatagramPacket(byte[] data, int offset, int

length, InetAddress destination, int port) public DatagramPacket(byte[] data, int length,

SocketAddress destination, int port) public DatagramPacket(byte[] data, int offset, int

length, SocketAddress destination, int port)


Exemple

String s = "On essaie…";byte[] data = s.getBytes("ASCII");

try { InetAddress ia =

InetAddress.getByName("www.liafa.jussieu.fr"); int port = 7;// existe-t-il? DatagramPacket dp = new DatagramPacket(data,

data.length, ia, port);}catch (IOException ex)}


Méthodes

Adresses public InetAddress getAddress( ) public int getPort( ) public SocketAddress getSocketAddress( ) public void setAddress(InetAddress remote) public void setPort(int port) public void setAddress(SocketAddress remote)


Méthodes (suite)

Manipulation des données: public byte[] getData( ) public int getLength( ) public int getOffset( ) public void setData(byte[] data) public void setData(byte[] data, int offset,

int length ) public void setLength(int length)


Exemple

import java.net.*;public class DatagramExample { public static void main(String[] args) { String s = "Essayons."; byte[] data = s.getBytes( ); try { InetAddress ia = InetAddress.getByName("www.liafa.jussieu.fr"); int port =7; DatagramPacket dp = new DatagramPacket(data, data.length, ia, port); System.out.println(" Un packet pour" + dp.getAddress( ) + " port " +

dp.getPort( )); System.out.println("il y a " + dp.getLength( ) +

" bytes dans le packet"); System.out.println( new String(dp.getData( ), dp.getOffset( ), dp.getLength( ))); } catch (UnknownHostException e) { System.err.println(e); } }}


DatagramSocket

Constructeurs public DatagramSocket( ) throws SocketException public DatagramSocket(int port) throws

SocketException public DatagramSocket(int port, InetAddress

interface) throws SocketException public DatagramSocket(SocketAddress interface)

throws SocketException (protected DatagramSocket(DatagramSocketImpl

impl) throws SocketException)


Exemple

java.net.*;public class UDPPortScanner { public static void main(String[] args) { for (int port = 1024; port <= 65535; port++) { try { // exception si utilisé DatagramSocket server = new DatagramSocket(port); server.close( ); } catch (SocketException ex) { System.out.println("Port occupé" + port + "."); } // end try } // end for }}


Envoyer et recevoir

public void send(DatagramPacket dp) throws IOException

public void receive(DatagramPacket dp) throws IOException


Un exemple: Echo

UDPServeur UDPEchoServeur

UDPEchoClient• SenderThread• ReceiverThread


Echo: UDPServeur

import java.net.*;import java.io.*; public abstract class UDPServeur extends Thread { private int bufferSize; protected DatagramSocket sock; public UDPServeur(int port, int bufferSize) throws SocketException { this.bufferSize = bufferSize; this.sock = new DatagramSocket(port); } public UDPServeur(int port) throws SocketException { this(port, 8192); } public void run() { byte[] buffer = new byte[bufferSize]; while (true) { DatagramPacket incoming = new DatagramPacket(buffer, buffer.length); try { sock.receive(incoming); this.respond(incoming); } catch (IOException e) { System.err.println(e); } } // end while } public abstract void respond(DatagramPacket request);}


UDPEchoServeur

public class UDPEchoServeur extends UDPServeur { public final static int DEFAULT_PORT = 2222; public UDPEchoServeur() throws SocketException { super(DEFAULT_PORT); } public void respond(DatagramPacket packet) { try { byte[] data = new byte[packet.getLength()]; System.arraycopy(packet.getData(), 0, data, 0, packet.getLength()); try { String s = new String(data, "8859_1"); System.out.println(packet.getAddress() + " port " + packet.getPort() + " reçu " + s); } catch (java.io.UnsupportedEncodingException ex) {} DatagramPacket outgoing = new DatagramPacket(packet.getData(), packet.getLength(), packet.getAddress(), packet.getPort()); sock.send(outgoing); } catch (IOException ex) { System.err.println(ex); } }}


Client: UDPEchoClient

public class UDPEchoClient { public static void lancer(String hostname, int port) { try { InetAddress ia = InetAddress.getByName(hostname); SenderThread sender = new SenderThread(ia, port); sender.start(); Thread receiver = new ReceiverThread(sender.getSocket()); receiver.start(); } catch (UnknownHostException ex) { System.err.println(ex); } catch (SocketException ex) { System.err.println(ex); }

} // end lancer}


ReceiverThread

class ReceiverThread extends Thread { DatagramSocket socket; private boolean stopped = false; public ReceiverThread(DatagramSocket ds) throws SocketException { this.socket = ds; } public void halt() { this.stopped = true; } public DatagramSocket getSocket(){ return socket; } public void run() { byte[] buffer = new byte[65507]; while (true) { if (stopped) return; DatagramPacket dp = new DatagramPacket(buffer, buffer.length); try { socket.receive(dp); String s = new String(dp.getData(), 0, dp.getLength()); System.out.println(s); Thread.yield(); } catch (IOException ex) {System.err.println(ex); } } } }


SenderThread

public class SenderThread extends Thread { private InetAddress server; private DatagramSocket socket; private boolean stopped = false; private int port; public SenderThread(InetAddress address, int port) throws SocketException { this.server = address; this.port = port; this.socket = new DatagramSocket(); this.socket.connect(server, port); } public void halt() { this.stopped = true; }//…


SenderThread

//… public DatagramSocket getSocket() { return this.socket; } public void run() { try { BufferedReader userInput = new BufferedReader(new

InputStreamReader(System.in)); while (true) { if (stopped) return; String theLine = userInput.readLine(); if (theLine.equals(".")) break; byte[] data = theLine.getBytes(); DatagramPacket output = new DatagramPacket(data, data.length, server, port); socket.send(output); Thread.yield(); } } // end try catch (IOException ex) {System.err.println(ex); } } // end run }


Autres méthodes

public void close( ) public int getLocalPort( ) public InetAddress getLocalAddress( ) public SocketAddress getLocalSocketAddress( ) public void connect(InetAddress host, int port) public void disconnect( ) public void disconnect( ) public int getPort( ) public InetAddress getInetAddress( ) public InetAddress getRemoteSocketAddress( )


Options

SO_TIMEOUT public synchronized void setSoTimeout(int timeout) throws

SocketException public synchronized int getSoTimeout( ) throws IOException

SO_RCVBUF public void setReceiveBufferSize(int size) throws SocketException public int getReceiveBufferSize( ) throws SocketException

SO_SNDBUF public void setSendBufferSize(int size) throws SocketException int getSendBufferSize( ) throws SocketException

SO_REUSEADDR (plusieurs sockets sur la même adresse) public void setReuseAddress(boolean on) throws SocketException boolean getReuseAddress( ) throws SocketException

SO_BROADCAST public void setBroadcast(boolean on) throws SocketException public boolean getBroadcast( ) throws SocketException


Multicast

143H. Fauconnier

M2-Internet Java

M2-Internet Java 4-144

R1

R2

R3 R4

sourceduplication

R1

R2

R3 R4

in-networkduplication

duplicatecreation/transmissionduplicate

duplicate

Broadcast Routing Deliver packets from srce to all other nodes Source duplication is inefficient:

Source duplication: how does source determine recipient addresses

H. Fauconnier


In-network duplication

Flooding: when node receives brdcst pckt, sends copy to all neighbors Problems: cycles & broadcast storm

Controlled flooding: node only brdcsts pkt if it hasn’t brdcst same packet before Node keeps track of pckt ids already brdcsted Or reverse path forwarding (RPF): only forward

pckt if it arrived on shortest path between node and source

Spanning tree No redundant packets received by any node

H. Fauconnier


A

B

G

DE

c

F

A

B

G

DE

c

F

(a) Broadcast initiated at A (b) Broadcast initiated at D

Spanning Tree

First construct a spanning tree Nodes forward copies only along

spanning tree

H. Fauconnier


A

B

G

DE

c

F1

2

3

4

5

(a)Stepwise construction of spanning tree

A

B

G

DE

c

F

(b) Constructed spanning tree

Spanning Tree: Creation Center node Each node sends unicast join message to

center node Message forwarded until it arrives at a node already

belonging to spanning tree

H. Fauconnier

Multicast

Groupe: adresse IP de classe D Un hôte peut joindre un groupe

Protocole pour établir les groupes (IGMP)

Protocole et algorithme pour le routage


H. Fauconnier

IGMP

IGMP (internet Group Management Protocol Entre un hôte et son routeur (multicast)

• Membership_query: du routeur vers tous les hôtes pour déterminer quels hôtes appartiennent à quels groupes

• Membership_report: des hôtes vers le routeur• Membership_leave: pour quitter un groupe

(optionnel)


H. Fauconnier

Multicast Routing: Problem Statement Goal: find a tree (or trees) connecting

routers having local mcast group members tree: not all paths between routers used source-based: different tree from each sender to rcvrs shared-tree: same tree used by all group members

Shared tree Source-based treesH. Fauconnier 1-

150M2-Internet Java

Approaches for building mcast treesApproaches: source-based tree: one tree per source

shortest path trees reverse path forwarding

group-shared tree: group uses one tree minimal spanning (Steiner) center-based trees

…we first look at basic approaches, then specific protocols adopting these approaches

H. Fauconnier 1-151

M2-Internet Java

Shortest Path Tree

mcast forwarding tree: tree of shortest path routes from source to all receivers Dijkstra’s algorithm

R1

R2

R3

R4

R5

R6 R7

21

6

3 45

i

router with attachedgroup member

router with no attachedgroup memberlink used for forwarding,i indicates order linkadded by algorithm

LEGENDS: source

H. Fauconnier 1-152

M2-Internet Java

Reverse Path Forwarding

if (mcast datagram received on incoming link on shortest path back to center)

then flood datagram onto all outgoing links else ignore datagram

rely on router’s knowledge of unicast shortest path from it to sender

each router has simple forwarding behavior:

H. Fauconnier 1-153

M2-Internet Java

Reverse Path Forwarding: example

• result is a source-specific reverse SPT– may be a bad choice with asymmetric links

R1

R2

R3

R4

R5

R6 R7


router with no attachedgroup memberdatagram will be forwarded

LEGENDS: source

datagram will not be forwarded

H. Fauconnier 1-154

M2-Internet Java

Reverse Path Forwarding: pruning forwarding tree contains subtrees with no mcast

group members no need to forward datagrams down subtree “prune” msgs sent upstream by router with no

downstream group members

R1

R2

R3

R4

R5

R6 R7

router with attachedgroup memberrouter with no attachedgroup member

prune message

LEGENDS: source

links with multicastforwarding

P

P

P

H. Fauconnier 1-155

M2-Internet Java

Shared-Tree: Steiner Tree

Steiner Tree: minimum cost tree connecting all routers with attached group members

problem is NP-complete excellent heuristics exists not used in practice:

computational complexity information about entire network needed monolithic: rerun whenever a router needs

to join/leave

H. Fauconnier 1-156

M2-Internet Java

Center-based trees

single delivery tree shared by all one router identified as “center” of tree to join:

edge router sends unicast join-msg addressed to center router

join-msg “processed” by intermediate routers and forwarded towards center

join-msg either hits existing tree branch for this center, or arrives at center

path taken by join-msg becomes new branch of tree for this router

H. Fauconnier 1-157

M2-Internet Java

Center-based trees: an example

Suppose R6 chosen as center:

R1

R2

R3

R4

R5

R6 R7


router with no attachedgroup member

path order in which join messages generated

LEGEND

21

3

1

H. Fauconnier 1-158

M2-Internet Java

Internet Multicasting Routing: DVMRP

DVMRP: distance vector multicast routing protocol, RFC1075

flood and prune: reverse path forwarding, source-based tree RPF tree based on DVMRP’s own routing tables

constructed by communicating DVMRP routers no assumptions about underlying unicast initial datagram to mcast group flooded

everywhere via RPF routers not wanting group: send upstream

prune msgs

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DVMRP: continued…

soft state: DVMRP router periodically (1 min.) “forgets” branches are pruned: mcast data again flows down unpruned branch downstream router: reprune or else continue to

receive data routers can quickly regraft to tree

following IGMP join at leaf odds and ends

commonly implemented in commercial routers Mbone routing done using DVMRP

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Tunneling

Q: How to connect “islands” of multicast routers in a “sea” of unicast routers?

mcast datagram encapsulated inside “normal” (non-multicast-addressed) datagram

normal IP datagram sent thru “tunnel” via regular IP unicast to receiving mcast router

receiving mcast router unencapsulates to get mcast datagram

physical topology logical topology

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PIM: Protocol Independent Multicast

not dependent on any specific underlying unicast routing algorithm (works with all)

two different multicast distribution scenarios :

Dense: group members densely

packed, in “close” proximity.

bandwidth more plentiful

Sparse: # networks with group members

small wrt # interconnected networks

group members “widely dispersed”

bandwidth not plentiful

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Consequences of Sparse-Dense Dichotomy: Dense group membership by

routers assumed until routers explicitly prune

data-driven construction on mcast tree (e.g., RPF)

bandwidth and non-group-router processing profligate

Sparse: no membership until

routers explicitly join receiver- driven

construction of mcast tree (e.g., center-based)

bandwidth and non-group-router processing conservative

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PIM- Dense Mode

flood-and-prune RPF, similar to DVMRP but underlying unicast protocol provides RPF info for

incoming datagram less complicated (less efficient) downstream flood than

DVMRP reduces reliance on underlying routing algorithm

has protocol mechanism for router to detect it is a leaf-node router

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PIM - Sparse Mode

center-based approach router sends join msg

to rendezvous point (RP) intermediate routers

update state and forward join

after joining via RP, router can switch to source-specific tree increased performance:

less concentration, shorter paths

R1

R2

R3

R4

R5

R6R7

join

join

join

all data multicastfrom rendezvouspoint

rendezvouspoint

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PIM - Sparse Mode

sender(s): unicast data to RP,

which distributes down RP-rooted tree

RP can extend mcast tree upstream to source

RP can send stop msg if no attached receivers “no one is listening!”

R1

R2

R3

R4

R5

R6R7

join

join

join

all data multicastfrom rendezvouspoint

rendezvouspoint

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Multicast

Géré par les routeurs Pas de garantie…

Importance du ttl• (Évaluation)

– Local:0

– Sous-réseau local:1

– Pays:48

– Continent:64

– Le monde:255


H. Fauconnier

Multicast

Un groupe est identifié par une adresse IP (classe D) entre 224.0.0.0 et 239.255.255.255

Une adresse multicast peut avoir un nom Exemple ntp.mcast.net 224.0.1.1


H. Fauconnier

Sockets multicast

Extension de DatagramSocket public class MulticastSocket extends

DatagramSocket

Principe: Créer une MulticastSocket Rejoindre un group: joinGroup()

• Créer DatagramPacket – Receive()

• leaveGroup() Close()


Création

try { MulticastSocket ms = new MulticastSocket( ); // send datagrams...}catch (SocketException se){System.err.println(se);}-------try { SocketAddress address = new

InetSocketAddress("192.168.254.32", 4000); MulticastSocket ms = new MulticastSocket(address);

// receive datagrams...}catch (SocketException ex) {System.err.println(ex);}


Création

try { MulticastSocket ms = new MulticastSocket(null);ms.setReuseAddress(false); SocketAddress address = new InetSocketAddress(4000); ms.bind(address); // receive datagrams...

}catch (SocketException ex) { System.err.println(ex);}


Rejoindre…

try { MulticastSocket ms = new MulticastSocket(4000);InetAddress ia = InetAddress.getByName("224.2.2.2"); ms.joinGroup(ia); byte[] buffer = new byte[8192]; while (true) {

DatagramPacket dp = new DatagramPacket(buffer, buffer.length); ms.receive(dp);

String s = new String(dp.getData( ), "8859_1");System.out.println(s);

}}catch (IOException ex) { System.err.println(ex);}


send

try { InetAddress ia = InetAddress.getByName("experiment.mcast.net");byte[] data = "un packet…\r\n".getBytes( ); int port = 4000;DatagramPacket dp = new DatagramPacket(data,

data.length, ia, port); MulticastSocket ms = new MulticastSocket( );ms.send(dp,64);

}catch (IOException ex) {System.err.println(ex);}


Documents

Chapitre II M2 Internet et java H. Fauconnier 1-1 M2-Internet Java