socket udphf/verif/ens/an09-10/internet/udp-multicast.pdf · udp provides unreliable transfer of...
TRANSCRIPT
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Socket UDP
H. Fauconnier 1-1 M2-Internet Java
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UDP
H. Fauconnier M2-Internet Java 2
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M2-Internet Java 3
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
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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 4 H. Fauconnier
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M2-Internet Java 5
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
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M2-Internet Java 6
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
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M2-Internet Java 7
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
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M2-Internet Java 8
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
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M2-Internet Java 9
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
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M2-Internet Java 10
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
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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 11 H. Fauconnier
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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 12
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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 13
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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 14
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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 15
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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 16
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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 17
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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 18
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Envoyer et recevoir
public void send(DatagramPacket dp) throws IOException
public void receive(DatagramPacket dp) throws IOException
H. Fauconnier M2-Internet Java 19
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Un exemple: Echo
UDPServeur UDPEchoServeur
UDPEchoClient • SenderThread • ReceiverThread
H. Fauconnier M2-Internet Java 20
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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 21
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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 22
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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 23
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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 24
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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 25
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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 26
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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 27
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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 28
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Multicast
29 H. Fauconnier
M2-Internet Java
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M2-Internet Java 4-30
R1
R2
R3 R4
source duplication
R1
R2
R3 R4
in-network duplication
duplicate creation/transmission duplicate
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
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M2-Internet Java 4-31
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
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M2-Internet Java 4-32
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
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M2-Internet Java 4-33
A
B
G
D E
c
F 1
2
3
4
5
(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
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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 4-34 H. Fauconnier
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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 groupe
• Membership_report: des hôtes vers le routeur • Membership_leave: pour quitter un groupe (optionnel)
M2-Internet Java 4-35 H. Fauconnier
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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 1-36 M2-Internet Java
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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
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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
2 1
6
3 4 5
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
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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:
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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
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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 attached group member router with no attached group member prune message
LEGEND S: source
links with multicast forwarding
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 attached group member router with no attached group member path order in which join messages generated
LEGEND
2 1
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
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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
R6 R7
join
join
join
all data multicast from rendezvous point
rendezvous point
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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
R6 R7
join
join
join
all data multicast from rendezvous point
rendezvous point
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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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