ServerSocket H. Fauconnier 1-1 M2-Internet Java. Principe 1. Création dun ServerSocket par constructeur 2. Association (bind) de la socket à une adresse

ServerSocket

H. Fauconnier 1-1M2-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 2

Constructeurs

public ServerSocket(int port) throws BindException, IOException

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

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

IOException Ces constructeurs associent un port et une

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


Exemple

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

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

+ port ); } } }


Remarques

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

connexions en attente on peut choisir une adresse particulière

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

explicite:• public void bind(SocketAddress endpoint)

throws IOException• public void bind(SocketAddress endpoint,

int queueLength) throws IOException


Exemple

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


Connexion accept()

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


Exemple

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

OutputStreamWriter( connection.getOutputStream( ));

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


Exemple plus complet

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


Exemple suite

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

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


Fermeture

public void close( ) throws IOException

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


Serveur echo

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


serveur echo: EchoThread

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

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


run

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


Remarques

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

on peut aussi utiliser des entrées/sorties non bloquantes


Autres méthodes

public InetAddress getInetAddress( ) public int getLocalPort( )


Options

SO_TIMEOUT SO_REUSEADDR SO_RCVBUF public void setPerformancePreferences(int

connectionTime, int latency, int bandwidth


Socket UDP

H. Fauconnier 1-18

M2-Internet Java

UDP


M2-Internet Java 20

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 21H. Fauconnier

M2-Internet Java 22

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 23

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 24

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 25

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 26

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 27

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 28H. 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)


http://download-llnw.oracle.com/javase/1.5.0/docs/api/java/net/DatagramPacket.html

Exemple

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

try { InetAddress ia =

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

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


Méthodes

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


http://download-llnw.oracle.com/javase/6/docs/api/java/net/InetAddress.html

http://download-llnw.oracle.com/javase/6/docs/api/java/net/SocketAddress.html

Méthodes (suite)

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

int length ) public void setLength(int length)


Exemple

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

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

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


DatagramSocket

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

SocketException public DatagramSocket(int port, InetAddress

interface) throws SocketException public DatagramSocket(SocketAddress interface)

throws SocketException (protected DatagramSocket(DatagramSocketImpl

impl) throws SocketException)


http://download-llnw.oracle.com/javase/6/docs/api/java/net/DatagramSocket.html

Exemple

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


Envoyer et recevoir

public void send(DatagramPacket dp) throws IOException

public void receive(DatagramPacket dp) throws IOException


Un exemple: Echo

UDPServeur UDPEchoServeur

UDPEchoClient• SenderThread• ReceiverThread


Echo: UDPServeur

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


UDPEchoServeur

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


Client: UDPEchoClient

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

} // end lancer}


ReceiverThread

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


SenderThread

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


SenderThread

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

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


Autres méthodes

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


Options

SO_TIMEOUT public synchronized void setSoTimeout(int timeout) throws

SocketException public synchronized int getSoTimeout( ) throws IOException

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

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

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

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


Multicast

46H. Fauconnier

M2-Internet Java

M2-Internet Java 4-47

R1

R2

R3 R4

sourceduplication

R1

R2

R3 R4

in-networkduplication

duplicatecreation/transmissionduplicate

duplicate

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

Source duplication: how does source determine recipient addresses

H. Fauconnier


In-network duplication

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

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

pckt if it arrived on shortest path between node and source

Spanning tree No redundant packets received by any node

H. Fauconnier


A

B

G

DE

c

F

A

B

G

DE

c

F

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

Spanning Tree

First construct a spanning tree Nodes forward copies only along

spanning tree

H. Fauconnier


A

B

G

DE

c

F1

2

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5

(a)Stepwise construction of spanning tree

A

B

G

DE

c

F

(b) Constructed spanning tree

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

center node Message forwarded until it arrives at a node already

belonging to spanning tree

H. Fauconnier

Multicast

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

Protocole pour établir les groupes (IGMP)

Protocole et algorithme pour le routage


H. Fauconnier

IGMP

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

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

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

(optionnel)


H. Fauconnier

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

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

Shared tree Source-based treesH. Fauconnier 1-

53M2-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 1-54

M2-Internet Java

Shortest Path Tree

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

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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 1-55

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 1-56

M2-Internet Java

Reverse Path Forwarding: example

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

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router with no attachedgroup memberdatagram will be forwarded

LEGENDS: source

datagram will not be forwarded

H. Fauconnier 1-57

M2-Internet Java

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

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

downstream group members

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router with attachedgroup memberrouter with no attachedgroup member

prune message

LEGENDS: source

links with multicastforwarding

P

P

P

H. Fauconnier 1-58

M2-Internet Java

Shared-Tree: Steiner Tree

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

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

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

to join/leave

H. Fauconnier 1-59

M2-Internet Java

Center-based trees

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

edge router sends unicast join-msg addressed to center router

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

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

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

H. Fauconnier 1-60

M2-Internet Java

Center-based trees: an example

Suppose R6 chosen as center:

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router with no attachedgroup member

path order in which join messages generated

LEGEND

21

3

1

H. Fauconnier 1-61

M2-Internet Java

Internet Multicasting Routing: DVMRP

DVMRP: distance vector multicast routing protocol, RFC1075

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

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

everywhere via RPF routers not wanting group: send upstream

prune msgs

H. Fauconnier 1-62

M2-Internet Java

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 1-63

M2-Internet Java

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 1-64

M2-Internet Java

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 1-65

M2-Internet Java

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 1-66

M2-Internet Java

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 1-67

M2-Internet Java

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

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join

join

join

all data multicastfrom rendezvouspoint

rendezvouspoint

H. Fauconnier 1-68

M2-Internet Java

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!”

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join

join

join

all data multicastfrom rendezvouspoint

rendezvouspoint

H. Fauconnier 1-69

M2-Internet Java

Multicast

Géré par les routeurs Pas de garantie…

Importance du ttl• (Évaluation)

– Local:0

– Sous-réseau local:1

– Pays:48

– Continent:64

– Le monde:255


H. Fauconnier

Multicast

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

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


H. Fauconnier

Sockets multicast

Extension de DatagramSocket public class MulticastSocket extends

DatagramSocket

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

• Créer DatagramPacket – Receive()

• leaveGroup() Close()


Création

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

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

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


Création

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

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


Rejoindre…

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

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

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

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


send

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

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

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


Documents

ServerSocket H. Fauconnier 1-1 M2-Internet Java. Principe 1. Création dun ServerSocket par constructeur 2. Association (bind) de la socket à une adresse