Chapitre II M2 Internet et java H. Fauconnier 1-1 M2-Internet Java
Mar 30, 2015
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
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Entrées-sorties java
Streams Output streams Input streams Filter streams Readers et writer
(non blocking I/O)
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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
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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( )
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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;}
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Filtres
Chainage des filtres:DataOutputStream dout = new
DataOutputStream(new BufferedOutputStream(new FileOutputStream ("data.txt")));
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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
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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
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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
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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( );
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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( );
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digest
public class DigestOutputStream extends FilterOutputStream
public class DigestInputStream extends FilterInputStream
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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( );
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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);
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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);
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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);}
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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
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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"));
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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( ); }
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Filtres
BufferedReader BufferedWriter LineNumberReader PushbackReader PrintWriter
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Threads
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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
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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
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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){ } }}
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Suite
public static void main(String[] args) { new ThreadAffiche("PING", 10).start(); new ThreadAffiche("PONG", 30).start(); new ThreadAffiche("Splash!",60).start(); }
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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.
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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){ } }}
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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();}
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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!
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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); } }
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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
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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()); }}
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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
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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
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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); } }}
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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
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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)
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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; }}
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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()
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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()
}
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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; }
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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(); }
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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(); }
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Réseau et Java
Rappels Tcp-udp
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I) Introduction
Les couches
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Couche Internet
Datagramme IPv4
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Couche transport
TCP Mode connecté, flot bidirectionnel, sûr,
contrôle de la congestion Téléphone
UDP Mode non connecté, messages, sans
garantie, déséquencement Poste
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Adresses internet
Adresse IP: adresse réseau + site sur le réseau
Exemple:
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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
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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
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Quelques ports
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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
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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
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Client-serveur
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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
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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)
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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
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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 ??"); }
}
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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 ??"); }
}
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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"); } }
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Mon adresse
public static String MonAdresse() { try { InetAddress moi = InetAddress.getLocalHost(); return( moi.getHostAddress()); } catch (UnknownHostException ex) { return("Mon adresse est inconnue"); } }
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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); }
}
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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
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NetworkInterface
Exemple:try {
NetworkInterface ni = NetworkInterface.getByName("eth0"); if (ni == null) {
System.err.println(" pas de:eth0" ); }
} catch (SocketException ex) { }
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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(); } }
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sockets (client)
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M2-Internet Java
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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
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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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M2-Internet Java 70
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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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
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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
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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?
M2-Internet Java 79H. Fauconnier
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
H. Fauconnier M2-Internet Java 81
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
H. Fauconnier M2-Internet Java 82
Attention!
L’accès aux ports est souvent restreint Des firewall peuvent empêcher les
connexions Il faut être root pour utiliser des ports
réservés…
H. Fauconnier M2-Internet Java 83
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
H. Fauconnier M2-Internet Java 84
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 } } }
H. Fauconnier M2-Internet Java 85
Attention
Cet exemple peut ne pas bien fonctionner… Pour des raisons de sécurité la tentative de
connexion peut être bloquante
H. Fauconnier M2-Internet Java 86
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
H. Fauconnier M2-Internet Java 87
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);
H. Fauconnier M2-Internet Java 88
Obtenir des infos…
public InetAddress getInetAddress( ) public int getPort( ) public InetAddress getLocalAddress( ) public int getLocalPort( )
H. Fauconnier M2-Internet Java 89
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); } } }
H. Fauconnier M2-Internet Java 90
Communiquer…
public InputStream getInputStream( ) throws IOException
public OutputStream getOutputStream( ) throws IOException
H. Fauconnier M2-Internet Java 91
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); } } }
H. Fauconnier M2-Internet Java 92
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) {} } }
}
H. Fauconnier M2-Internet Java 93
Echo suite
catch (IOException ex) { System.err.println(ex);} finally { try { if (networkIn != null) networkIn.close(); if (out != null) out.close(); } catch (IOException ex) {} }
H. Fauconnier M2-Internet Java 94
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 )
H. Fauconnier M2-Internet Java 95
En plus
public boolean isClosed( ) public boolean isConnected( ) public boolean isBound( ) public void shutdownInput( ) throws
IOException public void shutdownOutput( )
throws IOException
H. Fauconnier M2-Internet Java 96
Et aussi
TCP_NODELAY SO_TIMEOUT SO_LINGER SO_SNDBUF SO_RCVBUF SO_KEEPALIVE OOBINLINE SO_REUSEADDR
H. Fauconnier M2-Internet Java 97
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)
H. Fauconnier M2-Internet Java 99
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
H. Fauconnier M2-Internet Java 100
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 ); } } }
H. Fauconnier M2-Internet Java 101
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
H. Fauconnier M2-Internet Java 102
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); }}
H. Fauconnier M2-Internet Java 103
Connexion accept()
crée et retourne une nouvelle socket pour la connexion associée (IP, port)(IP, port)
H. Fauconnier M2-Internet Java 104
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( );}
H. Fauconnier M2-Internet Java 105
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;
H. Fauconnier M2-Internet Java 106
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); } }
H. Fauconnier M2-Internet Java 107
Fermeture
public void close( ) throws IOException
Ferme le ServerSocket et toutes les connexions créées par accept sur la ServerSocket
H. Fauconnier M2-Internet Java 108
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"); } } }
H. Fauconnier M2-Internet Java 109
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); } }
H. Fauconnier M2-Internet Java 110
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();} } }
H. Fauconnier M2-Internet Java 111
Remarques
utilisation des threads pour traiter le service et éviter de faire attendre les clients
on peut aussi utiliser des entrées/sorties non bloquantes
H. Fauconnier M2-Internet Java 112
Autres méthodes
public InetAddress getInetAddress( ) public int getLocalPort( )
H. Fauconnier M2-Internet Java 113
Options
SO_TIMEOUT SO_REUSEADDR SO_RCVBUF public void setPerformancePreferences(int
connectionTime, int latency, int bandwidth
H. Fauconnier M2-Internet Java 114
Socket UDP
H. Fauconnier 1-115
M2-Internet Java
UDP
H. Fauconnier M2-Internet Java 116
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
M2-Internet Java 118H. Fauconnier
M2-Internet Java 119
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
M2-Internet Java 120
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
M2-Internet Java 121
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
M2-Internet Java 122
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
M2-Internet Java 123
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
M2-Internet Java 124
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?
M2-Internet Java 125H. Fauconnier
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)
H. Fauconnier M2-Internet Java 126
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)}
H. Fauconnier M2-Internet Java 127
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)
H. Fauconnier M2-Internet Java 128
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)
H. Fauconnier M2-Internet Java 129
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); } }}
H. Fauconnier M2-Internet Java 130
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)
H. Fauconnier M2-Internet Java 131
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 }}
H. Fauconnier M2-Internet Java 132
Envoyer et recevoir
public void send(DatagramPacket dp) throws IOException
public void receive(DatagramPacket dp) throws IOException
H. Fauconnier M2-Internet Java 133
Un exemple: Echo
UDPServeur UDPEchoServeur
UDPEchoClient• SenderThread• ReceiverThread
H. Fauconnier M2-Internet Java 134
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);}
H. Fauconnier M2-Internet Java 135
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); } }}
H. Fauconnier M2-Internet Java 136
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}
H. Fauconnier M2-Internet Java 137
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); } } } }
H. Fauconnier M2-Internet Java 138
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; }//…
H. Fauconnier M2-Internet Java 139
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 }
H. Fauconnier M2-Internet Java 140
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( )
H. Fauconnier M2-Internet Java 141
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
H. Fauconnier M2-Internet Java 142
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
M2-Internet Java 4-145
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
M2-Internet Java 4-146
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
M2-Internet Java 4-147
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
M2-Internet Java 4-148
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)
M2-Internet Java 4-149
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 attachedgroup member
router with no attachedgroup memberdatagram will be forwarded
LEGENDS: source
datagram will not be forwarded
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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
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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
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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
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Center-based trees: an example
Suppose R6 chosen as center:
R1
R2
R3
R4
R5
R6 R7
router with attachedgroup member
router with no attachedgroup member
path order in which join messages generated
LEGEND
21
3
1
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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
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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
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Sockets multicast
Extension de DatagramSocket public class MulticastSocket extends
DatagramSocket
Principe: Créer une MulticastSocket Rejoindre un group: joinGroup()
• Créer DatagramPacket – Receive()
• leaveGroup() Close()
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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);}
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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);}
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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);}
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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);}
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