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

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

2 Sommaire Rappels java Entrées-sorties Thread Rappels tcp-udp Socket tcp et SocketServer Socket udp compléments H. Fauconnier M2-Internet Java 2

3 Entrées-sorties java Streams Output streams Input streams Filter streams Readers et writer (non blocking I/O) H. Fauconnier M2-Internet Java 3

4 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 H. Fauconnier M2-Internet Java 4

5 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( ) H. Fauconnier M2-Internet Java 5

6 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; } H. Fauconnier M2-Internet Java 6

7 Filtres Chainage des filtres: DataOutputStream dout = new DataOutputStream(new BufferedOutputStream(new FileOutputStream ("data.txt"))); H. Fauconnier M2-Internet Java 7

8 Filtres Streams avec buffer BufferedInputStream BufferedOutputStream PrintStream (System.out) PrintStream 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 H. Fauconnier M2-Internet Java 8

9 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 H. Fauconnier M2-Internet Java 9

10 Compression public class DeflaterOutputStream extends FilterOutputStreamDeflaterOutputStream public class InflaterInputStream extends FilterInputStreamInflaterInputStream public class GZIPOutputStream extends DeflaterOutputStreamGZIPOutputStream public class GZIPInputStream extends InflaterInputStreamGZIPInputStream public class ZipOutputStream extends DeflaterOutputStreamZipOutputStream public class ZipInputStream extends InflaterInputStreamZipInputStream H. Fauconnier M2-Internet Java 10

11 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( ); H. Fauconnier M2-Internet Java 11

12 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( ); H. Fauconnier M2-Internet Java 12

13 digest public class DigestOutputStream extends FilterOutputStreamDigestOutputStream public class DigestInputStream extends FilterInputStreamDigestInputStream H. Fauconnier M2-Internet Java 13

14 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( ); H. Fauconnier M2-Internet Java 14

15 Cryptage décryptage public CipherInputStream(InputStream in, Cipher c)CipherInputStreamCipher public CipherOutputStream(OutputStream out, Cipher c)CipherOutputStreamCipher Exemple byte[] 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); H. Fauconnier M2-Internet Java 15

16 Exemple Stri ng 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); H. Fauconnier M2-Internet Java 16

17 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); } H. Fauconnier M2-Internet Java 17

18 Readers et Writers Hiérarchie de classe pour les caractères (avec encodage) au lieu doctets. Writer et Reader classes abstraites WriterReader OutputStreamWriter InputStreamReader Filtres BufferedReader, BufferedWriter LineNumberReader PushbackReader PrintReader H. Fauconnier M2-Internet Java 18

19 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")); H. Fauconnier M2-Internet Java 19

20 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( ); } H. Fauconnier M2-Internet Java 20

21 Filtres BufferedReader BufferedWriter LineNumberReader PushbackReader PrintWriter H. Fauconnier M2-Internet Java 21

22 Threads H. Fauconnier M2-Internet Java 22

23 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 H. Fauconnier M2-Internet Java 23

24 Principes de base extension de la classe ThreadThread 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 H. Fauconnier M2-Internet Java 24

25 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){ } H. Fauconnier M2-Internet Java 25

26 Suite public static void main(String[] args) { new ThreadAffiche("PING", 10).start(); new ThreadAffiche("PONG", 30).start(); new ThreadAffiche("Splash!",60).start(); } H. Fauconnier M2-Internet Java 26

27 Alternative: RunnableRunnable 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. H. Fauconnier M2-Internet Java 27

28 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){ } H. Fauconnier M2-Internet Java 28

29 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(); } H. Fauconnier M2-Internet Java 29

30 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! H. Fauconnier M2-Internet Java 30

31 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); } H. Fauconnier M2-Internet Java 31

32 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 H. Fauconnier M2-Internet Java 32

33 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()); } H. Fauconnier M2-Internet Java 33

34 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 H. Fauconnier M2-Internet Java 34

35 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 H. Fauconnier M2-Internet Java 35

36 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); } H. Fauconnier M2-Internet Java 36

37 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 H. Fauconnier M2-Internet Java 37

38 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) H. Fauconnier M2-Internet Java 38

39 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; } H. Fauconnier M2-Internet Java 39

40 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() H. Fauconnier M2-Internet Java 40

41 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 condition notifyAll(); // ou notify() } H. Fauconnier M2-Internet Java 41

42 Exemple (file: rappel Cellule) public class Cellule { private Cellule 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 getSuivant(){ return suivant; } public void setSuivant(Cellule s){ this.suivant=s; } H. Fauconnier M2-Internet Java 42

43 Files synchronisées class File { protected Cellule tete, queue; private int taille=0; public synchronized void enfiler(E item){ Cellule c=new Cellule (item); if (queue==null) tete=c; else{ queue.setSuivant(c); } c.setSuivant(null); queue = c; notifyAll(); } H. Fauconnier M2-Internet Java 43

44 File (suite) public synchronized E defiler() throws InterruptedException{ while (tete == null) wait(); Cellule tmp=tete; tete=tete.getSuivant(); if (tete == null) queue=null; return tmp.getElement(); } H. Fauconnier M2-Internet Java 44

45 Réseau et Java Rappels Tcp-udp H. Fauconnier M2-Internet Java 45

46 I) Introduction Les couches H. Fauconnier M2-Internet Java 46

47 Couche Internet Datagramme IPv4 H. Fauconnier M2-Internet Java 47

48 Couche transport TCP Mode connecté, flot bidirectionnel, sûr, contrôle de la congestion Téléphone UDP Mode non connecté, messages, sans garantie, déséquencement Poste H. Fauconnier M2-Internet Java 48

49 Adresses internet Adresse IP: adresse réseau + site sur le réseau Exemple: H. Fauconnier M2-Internet Java 49

50 Classe dadresses Internet ClasseBits départDébutFinNotation CIDRMasque ss-réseau Classe A / Classe B / Classe C / Classe D (mcast) /4non défini Classe E (réservée) /4non défini H. Fauconnier M2-Internet Java 50 ClasseNombre de réseaux possiblesNombre d'ordinateurs maxi sur chacun A B C

51 Connexion Adresse IP +port Ports réservés Ports libres H. Fauconnier M2-Internet Java 51

52 Quelques ports H. Fauconnier M2-Internet Java 52 ProtocolPortProtocol echo7TCP/UDP discard9TCP/UDP daytime13TCP/UDP FTP data20TCP FTP21TCP SSH22TCP telnet23TCP smtp25TCP time37TCP/UDP ProtocolPortProtocol whois43TCP finger79TCP HTTP80TCP POP3110TCP NNTP119TCP IMAP143TCP RMI Registry TCP

53 Proxys H. Fauconnier M2-Internet Java 53

54 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 H. Fauconnier M2-Internet Java 54

55 Client-serveur H. Fauconnier M2-Internet Java 55

56 Classes java.net.InetAddress (implements java.io.Serializable)InetAddressSerializable java.net.Inet4AddressInet4Address java.net.Inet6AddressInet6Address java.net.DatagramPacketDatagramPacket java.net.DatagramSocketDatagramSocket java.net.MulticastSocketMulticastSocket java.net.ServerSocketServerSocket javax.net.ssl.SSLServerSocketSSLServerSocket java.net.SocketSocket javax.net.ssl.SSLSocketSSLSocket java.net.SocketAddress (implements java.io.Serializable)SocketAddressSerializable java.net.InetSocketAddressInetSocketAddress H. Fauconnier M2-Internet Java 56

57 Classes Channel: java.nio.channels.spi.AbstractInterruptibleChannel (implements java.nio.channels.Channel, java.nio.channels.InterruptibleChannel)AbstractInterruptibleChannelChannelInterruptibleChannel java.nio.channels.SelectableChannel (implements java.nio.channels.Channel)SelectableChannelChannel java.nio.channels.spi.AbstractSelectableChannelAbstractSelectableChannel –java.nio.channels.DatagramChannel (implements java.nio.channels.ByteChannel, java.nio.channels.GatheringByteChannel, java.nio.channels.ScatteringByteChannel)DatagramChannelByteChannelGatheringByteChannelScatteringByteChannel –java.nio.channels.ServerSocketChannelServerSocketChannel –java.nio.channels.SocketChannel (implements java.nio.channels.ByteChannel, java.nio.channels.GatheringByteChannel, java.nio.channels.ScatteringByteChannel)SocketChannelByteChannelGatheringByteChannelScatteringByteChannel H. Fauconnier M2-Internet Java 57

58 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 H. Fauconnier M2-Internet Java 58

59 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 ??"); } H. Fauconnier M2-Internet Java 59

60 Exemples public static void main (String[] args){ try { InetAddress ad = InetAddress.getByName(" "); System.out.println(ad); } catch (UnknownHostException ex) { System.out.println(" ??"); } H. Fauconnier M2-Internet Java 60

61 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"); } H. Fauconnier M2-Internet Java 61

62 Mon adresse public static String MonAdresse() { try { InetAddress moi = InetAddress.getLocalHost(); return( moi.getHostAddress()); } catch (UnknownHostException ex) { return("Mon adresse est inconnue"); } } H. Fauconnier M2-Internet Java 62

63 InetAddress méthodes… public String getHostName( ) public byte[] getAddress( ) public String getHostAddress( ) Exemple: public static void main (String[] args) { try { InetAddress ia= InetAddress.getByName(" "); System.out.println(ia.getHostName( )); } catch (Exception ex) { System.err.println(ex); } } H. Fauconnier M2-Internet Java 63

64 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 H. Fauconnier M2-Internet Java 64

65 NetworkInterface Exemple: try { NetworkInterface ni = NetworkInterface.getByName("eth0"); if (ni == null) { System.err.println(" pas de:eth0" ); } } catch (SocketException ex) { } H. Fauconnier M2-Internet Java 65

66 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(); } H. Fauconnier M2-Internet Java 66

67 sockets (client) H. Fauconnier M2-Internet Java

68 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 which application 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

69 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. M2-Internet Java 69 H. Fauconnier

70 M2-Internet Java 70 Socket-programming using TCP TCP service: reliable transfer of bytes from one process to another process TCP with buffers, variables socket controlled by application developer controlled by operating system host or server process TCP with buffers, variables socket controlled by application developer controlled by operating system host or server internet H. Fauconnier

71 M2-Internet Java 71 Socket programming with TCP Client must contact server server process must first be running server must have created socket (door) that welcomes clients 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 H. Fauconnier

72 M2-Internet Java 72 Client/server socket interaction: TCP wait for incoming connection request connectionSocket = welcomeSocket.accept() create socket, port= x, for incoming request: welcomeSocket = ServerSocket() create socket, connect to hostid, port= x clientSocket = Socket() close connectionSocket read reply from clientSocket close clientSocket Server (running on hostid ) Client send request using clientSocket read request from connectionSocket write reply to connectionSocket TCP connection setup H. Fauconnier

73 M2-Internet Java 73 Client process 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. H. Fauconnier

74 M2-Internet Java 74 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 socket 3) server converts line to uppercase, sends back to client 4) client reads, prints modified line from socket ( inFromServer stream) H. Fauconnier

75 M2-Internet Java 75 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()); Create input stream Create client socket, connect to server Create output stream attached to socket H. Fauconnier

76 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(); } Create input stream attached to socket Send line to server Read line from server H. Fauconnier

77 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())); Create welcoming socket at port 6789 Wait, on welcoming socket for contact by client Create input stream, attached to socket H. Fauconnier

78 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 line from socket Create output stream, attached to socket Write out line to socket End of while loop, loop back and wait for another client connection H. Fauconnier

79 TCP observations & questions Server has two types of sockets: ServerSocket and Socket When client knocks on serverSockets 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 79 H. Fauconnier

80 Note Dans ce chapitre et le suivant on sintéresse aux sockets TCP, on verra les sockets UDP plus tard. H. Fauconnier M2-Internet Java 80

81 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

82 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

83 Attention! Laccès 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

84 Côté client Création: public Socket(InetAddress address, int port) throws IOExceptionInetAddressIOException Crée une socket + une connexion avec IP adresse et port En fait: Création dune socket locale attachée à un port + une adresse locale Etablissement de la connexion IOException en cas déchec H. Fauconnier M2-Internet Java 84

85 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

86 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

87 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 nimporte quel port H. Fauconnier M2-Internet Java 87

88 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

89 Obtenir des infos… public InetAddress getInetAddress( ) public int getPort( ) public InetAddress getLocalAddress( ) public int getLocalPort( ) H. Fauconnier M2-Internet Java 89

90 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

91 Communiquer… public InputStream getInputStream( ) throws IOException public OutputStream getOutputStream( ) throws IOException H. Fauconnier M2-Internet Java 91

92 Exemple: dayTime public static void time(String... hlist) { for (int i=0;i

93 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

94 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

95 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

96 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

97 Et aussi TCP_NODELAY SO_TIMEOUT SO_LINGER SO_SNDBUF SO_RCVBUF SO_KEEPALIVE OOBINLINE SO_REUSEADDR H. Fauconnier M2-Internet Java 97

98 ServerSocket H. Fauconnier M2-Internet Java

99 Principe 1. Création dun 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 accept 1. Communication getInputStream et getOutputStream 2. 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

100 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 lusage du port est exclusif et si le port est déjà occupé une exception est lancéeServerSocket public ServerSocket( ) throws IOException H. Fauconnier M2-Internet Java 100

101 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

102 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

103 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

104 Connexion accept() crée et retourne une nouvelle socket pour la connexion associée (IP, port)(IP, port) H. Fauconnier M2-Internet Java 104

105 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

106 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 = 65536) { System.out.println("Erreur port:"); return; } try { ServerSocket server = new ServerSocket(port); Socket connection = null; H. Fauconnier M2-Internet Java 106

107 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

108 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

109 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

110 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

111 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

112 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

113 Autres méthodes public InetAddress getInetAddress( ) public int getLocalPort( ) H. Fauconnier M2-Internet Java 113

114 Options SO_TIMEOUT SO_REUSEADDR SO_RCVBUF public void setPerformancePreferences(int connectionTime, int latency, int bandwidth H. Fauconnier M2-Internet Java 114

115 Socket UDP H. Fauconnier M2-Internet Java

116 UDP H. Fauconnier M2-Internet Java 116

117 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

118 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 118 H. Fauconnier

119 M2-Internet Java 119 Client/server socket interaction: UDP Server (running on hostid ) close clientSocket read datagram from clientSocket create socket, clientSocket = DatagramSocket() Client Create datagram with server IP and port=x; send datagram via clientSocket create socket, port= x. serverSocket = DatagramSocket() read datagram from serverSocket write reply to serverSocket specifying client address, port number H. Fauconnier

120 M2-Internet Java 120 Example: Java client (UDP) Output: sends packet (recall that TCP sent byte stream) Input: receives packet (recall thatTCP received byte stream) Client process client UDP socket H. Fauconnier

121 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(); Create input stream Create client socket Translate hostname to IP address using DNS H. Fauconnier

122 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 datagram to server Read datagram from server H. Fauconnier

123 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); Create datagram socket at port 9876 Create space for received datagram Receive datagram H. Fauconnier

124 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 addr port #, of sender Write out datagram to socket End of while loop, loop back and wait for another datagram Create datagram to send to client H. Fauconnier

125 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 servers IP address and/or port number? Can multiple clients use the server? M2-Internet Java 125 H. Fauconnier

126 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

127 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

129 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

130 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

131 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

132 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

133 Envoyer et recevoir public void send(DatagramPacket dp) throws IOException public void receive(DatagramPacket dp) throws IOException H. Fauconnier M2-Internet Java 133

134 Un exemple: Echo UDPServeur UDPEchoServeur UDPEchoClient SenderThread ReceiverThread H. Fauconnier M2-Internet Java 134

135 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

136 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

137 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

138 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

139 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

140 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

141 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 int getPort( ) public InetAddress getInetAddress( ) public InetAddress getRemoteSocketAddress( ) H. Fauconnier M2-Internet Java 141

142 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

143 Multicast 143 H. Fauconnier M2-Internet Java

144 R1 R2 R3R4 source duplication R1 R2 R3R4 in-network duplication duplicate creation/transmission duplicate Broadcast Routing Deliver packets from srce to all other nodes Source duplication is inefficient: r Source duplication: how does source determine recipient addresses H. Fauconnier

145 M2-Internet Java 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 hasnt 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

146 M2-Internet Java A B G D E c F A B G D E 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

147 M2-Internet Java A B G D E c F (a)Stepwise construction of spanning tree A B G D E 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

148 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 H. Fauconnier

149 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 H. Fauconnier

150 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 trees H. Fauconnier M2-Internet Java

151 Approaches for building mcast trees Approaches: 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 M2-Internet Java

152 Shortest Path Tree mcast forwarding tree: tree of shortest path routes from source to all receivers Dijkstras algorithm R1 R2 R3 R4 R5 R6 R i router with attached group member router with no attached group member link used for forwarding, i indicates order link added by algorithm LEGEND S: source H. Fauconnier M2-Internet Java

153 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 routers knowledge of unicast shortest path from it to sender each router has simple forwarding behavior: H. Fauconnier M2-Internet Java

154 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 attached group member router with no attached group member datagram will be forwarded LEGEND S: source datagram will not be forwarded H. Fauconnier M2-Internet Java

155 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 attached group member router with no attached group member prune message LEGEND S: source links with multicast forwarding P P P H. Fauconnier M2-Internet Java

156 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 M2-Internet Java

157 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 M2-Internet Java

158 Center-based trees: an example Suppose R6 chosen as center: R1 R2 R3 R4 R5 R6 R7 router with attached group member router with no attached group member path order in which join messages generated LEGEND H. Fauconnier M2-Internet Java

159 Internet Multicasting Routing: DVMRP DVMRP: distance vector multicast routing protocol, RFC1075 flood and prune: reverse path forwarding, source-based tree RPF tree based on DVMRPs 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 H. Fauconnier M2-Internet Java

160 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 H. Fauconnier M2-Internet Java

161 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 H. Fauconnier M2-Internet Java

162 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 H. Fauconnier M2-Internet Java

163 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 H. Fauconnier M2-Internet Java

164 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 H. Fauconnier M2-Internet Java

165 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 R6 R7 join all data multicast from rendezvous point rendezvous point H. Fauconnier M2-Internet Java

166 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 R6 R7 join all data multicast from rendezvous point rendezvous point H. Fauconnier M2-Internet Java

167 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 M2-Internet Java H. Fauconnier

168 Multicast Un groupe est identifié par une adresse IP (classe D) entre et Une adresse multicast peut avoir un nom Exemple ntp.mcast.net M2-Internet Java H. Fauconnier

169 Sockets multicast Extension de DatagramSocket public class MulticastSocket extends DatagramSocket Principe: Créer une MulticastSocket Rejoindre un group: joinGroup() Créer DatagramPacket –Receive() leaveGroup() Close() H. Fauconnier M2-Internet Java 169

170 Création try { MulticastSocket ms = new MulticastSocket( ); // send datagrams... }catch (SocketException se){System.err.println(se);} try { SocketAddress address = new InetSocketAddress(" ", 4000); MulticastSocket ms = new MulticastSocket(address); // receive datagrams... }catch (SocketException ex) {System.err.println(ex);} H. Fauconnier M2-Internet Java 170

171 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);} H. Fauconnier M2-Internet Java 171

172 Rejoindre… try { MulticastSocket ms = new MulticastSocket(4000); InetAddress ia = InetAddress.getByName(" "); 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);} H. Fauconnier M2-Internet Java 172

173 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);} H. Fauconnier M2-Internet Java 173


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