Socket UDP H. Fauconnier M2-Internet Java 1-1 UDP H. Fauconnier M2-Internet Java 2 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 H. Fauconnier 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”. M2-Internet Java 3 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 H. Fauconnier M2-Internet Java 4 Client/server socket interaction: UDP Server (running on hostid) create socket, port= x. serverSocket = DatagramSocket() read datagram from serverSocket write reply to serverSocket specifying client address, port number H. Fauconnier Client create socket, clientSocket = DatagramSocket() Create datagram with server IP and port=x; send datagram via clientSocket read datagram from clientSocket close clientSocket M2-Internet Java 5 Example: Java client (UDP) in p ut s tre am Client process m o nitor inF ro m U ser k ey b oa rd P ro c e ss Input: receives packet (recall thatTCP received “byte stream”) UDP p ac k et receiveP acket packet (recall that TCP sent “byte stream”) sendP acket Output: sends UDP p ac k et client UDP c lien tS o c k et socket to n etw ork H. Fauconnier UDP s oc k et fro m n etw o rk M2-Internet Java 6 Example: Java client (UDP) import java.io.*; import java.net.*; class UDPClient { public static void main(String args[]) throws Exception { Create input stream Create client socket Translate hostname to IP address using DNS 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(); H. Fauconnier M2-Internet Java 7 Example: Java client (UDP), cont. Create datagram with data-to-send, length, IP addr, port Send datagram to server DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 9876); clientSocket.send(sendPacket); DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length); Read datagram from server clientSocket.receive(receivePacket); String modifiedSentence = new String(receivePacket.getData()); System.out.println("FROM SERVER:" + modifiedSentence); clientSocket.close(); } } H. Fauconnier M2-Internet Java 8 Example: Java server (UDP) import java.io.*; import java.net.*; Create datagram socket at port 9876 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]; Create space for received datagram Receive datagram H. Fauconnier while(true) { DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length); serverSocket.receive(receivePacket); M2-Internet Java 9 Example: Java server (UDP), cont String sentence = new String(receivePacket.getData()); Get IP addr port #, of sender InetAddress IPAddress = receivePacket.getAddress(); int port = receivePacket.getPort(); String capitalizedSentence = sentence.toUpperCase(); sendData = capitalizedSentence.getBytes(); Create datagram to send to client DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, port); Write out datagram to socket serverSocket.send(sendPacket); } } } H. Fauconnier End of while loop, loop back and wait for another datagram M2-Internet Java 10 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? H. Fauconnier M2-Internet Java 11 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 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 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 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 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 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 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 Envoyer et recevoir public void send(DatagramPacket dp) throws IOException public void receive(DatagramPacket dp) throws IOException H. Fauconnier M2-Internet Java 19 Un exemple: Echo UDPServeur UDPEchoServeur UDPEchoClient • SenderThread • ReceiverThread H. Fauconnier M2-Internet Java 20 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 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 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 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 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 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 Autres méthodes public public public public public public public public public public H. Fauconnier void close( ) int getLocalPort( ) InetAddress getLocalAddress( ) SocketAddress getLocalSocketAddress( ) void connect(InetAddress host, int port) void disconnect( ) void disconnect( ) int getPort( ) InetAddress getInetAddress( ) InetAddress getRemoteSocketAddress( ) M2-Internet Java 27 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 Multicast H. Fauconnier M2-Internet Java 29 Broadcast Routing Deliver packets from srce to all other nodes Source duplication is inefficient: duplicate duplicate creation/transmission R1 R1 duplicate R2 R2 R3 R4 source duplication R3 R4 in-network duplication Source duplication: how does source determine recipient addresses H. Fauconnier M2-Internet Java 4-30 In-network duplication Flooding: when node receives brdcst pckt, sends copy to all neighbors Problems: cycles & broadcast storm Controlled flooding: node only brdcsts pkt if it hasn’t brdcst same packet before Node keeps track of pckt ids already brdcsted Or reverse path forwarding (RPF): only forward pckt if it arrived on shortest path between node and source Spanning tree No redundant packets received by any node H. Fauconnier M2-Internet Java 4-31 Spanning Tree First construct a spanning tree Nodes forward copies only along spanning tree A B c F A E c D F G (a) Broadcast initiated at A H. Fauconnier B E D G (b) Broadcast initiated at D M2-Internet Java 4-32 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 A A 3 B c 4 E F 1 2 B c D F 5 E D G G (a) Stepwise construction of spanning tree (b) Constructed spanning tree H. Fauconnier M2-Internet Java 4-33 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 M2-Internet Java 4-34 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) H. Fauconnier M2-Internet Java 4-35 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 H. Fauconnier Shared tree Source-based trees M2-Internet Java 1-36 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 1-37 Shortest Path Tree mcast forwarding tree: tree of shortest path routes from source to all receivers Dijkstra’s algorithm S: source LEGEND R1 1 2 R4 R2 3 R3 H. Fauconnier router with attached group member 5 4 R6 router with no attached group member R5 6 R7 i link used for forwarding, i indicates order link added by algorithm M2-Internet Java 1-38 Reverse Path Forwarding rely on router’s knowledge of unicast shortest path from it to sender each router has simple forwarding behavior: if (mcast datagram received on incoming link on shortest path back to center) then flood datagram onto all outgoing links else ignore datagram H. Fauconnier M2-Internet Java 1-39 Reverse Path Forwarding: example S: source LEGEND R1 R4 router with attached group member R2 R5 R3 • R6 R7 router with no attached group member datagram will be forwarded datagram will not be forwarded result is a source-specific reverse SPT – may be a bad choice with asymmetric links H. Fauconnier M2-Internet Java 1-40 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 LEGEND S: source R1 router with attached group member R4 R2 P R5 R3 H. Fauconnier R6 P R7 P router with no attached group member prune message links with multicast forwarding M2-Internet Java 1-41 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 1-42 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 1-43 Center-based trees: an example Suppose R6 chosen as center: LEGEND R1 3 R2 router with attached group member R4 2 R5 R3 H. Fauconnier 1 R6 1 router with no attached group member path order in which join messages generated R7 M2-Internet Java 1-44 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 M2-Internet Java 1-45 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 1-46 Tunneling Q: How to connect “islands” of multicast routers in a “sea” of unicast routers? physical topology logical topology 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 H. Fauconnier M2-Internet Java 1-47 PIM: Protocol Independent Multicast not dependent on any specific underlying unicast routing algorithm (works with all) two different multicast distribution scenarios : Dense: Sparse: group members densely # networks with group members packed, in “close” proximity. bandwidth more plentiful H. Fauconnier small wrt # interconnected networks group members “widely dispersed” bandwidth not plentiful M2-Internet Java 1-48 Consequences of Sparse-Dense Dichotomy: Dense group membership by Sparse: no membership until routers assumed until routers explicitly join routers explicitly prune receiver- driven data-driven construction construction of mcast on mcast tree (e.g., RPF) tree (e.g., center-based) bandwidth and non bandwidth and non-groupgroup-router processing router processing profligate conservative H. Fauconnier M2-Internet Java 1-49 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 1-50 PIM - Sparse Mode center-based approach router sends join msg to rendezvous point (RP) router can switch to source-specific tree increased performance: less concentration, shorter paths H. Fauconnier R4 join intermediate routers update state and forward join after joining via RP, R1 R2 R3 join R5 join R7 R6 all data multicast from rendezvous point rendezvous point M2-Internet Java 1-51 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!” H. Fauconnier R1 R4 join R2 R3 join R5 join R7 R6 all data multicast from rendezvous point rendezvous point M2-Internet Java 1-52 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 M2-Internet Java 4-53 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 M2-Internet Java 4-54 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 55 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);} H. Fauconnier M2-Internet Java 56 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 57 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);} H. Fauconnier M2-Internet Java 58 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 59