M2-Internet 1 H. Fauconnier. M2-Internet 2 Chapter 3: Application layer r 2.1 Principles of network applications r 2.2 Web and HTTP r 2.3 FTP r 2.4 Electronic.

Présentation au sujet: "M2-Internet 1 H. Fauconnier. M2-Internet 2 Chapter 3: Application layer r 2.1 Principles of network applications r 2.2 Web and HTTP r 2.3 FTP r 2.4 Electronic."— Transcription de la présentation:

1 M2-Internet 1 H. Fauconnier

2 M2-Internet 2 Chapter 3: Application layer r 2.1 Principles of network applications r 2.2 Web and HTTP r 2.3 FTP r 2.4 Electronic Mail  SMTP, POP3, IMAP r 2.5 DNS r 2.6 P2P applications H. Fauconnier

3 M2-Internet 3 Chapter 3: Application Layer Our goals: r conceptual, implementation aspects of network application protocols  transport-layer service models  client-server paradigm  peer-to-peer paradigm r learn about protocols by examining popular application-level protocols  HTTP  FTP  SMTP / POP3 / IMAP  DNS r programming network applications  socket API H. Fauconnier

4 M2-Internet 4 Some network apps r e-mail r web r instant messaging r remote login r P2P file sharing r multi-user network games r streaming stored video clips r social networks r voice over IP r real-time video conferencing r grid computing H. Fauconnier

5 M2-Internet 5 Creating a network app write programs that  run on (different) end systems  communicate over network  e.g., web server software communicates with browser software No need to write software for network-core devices  Network-core devices do not run user applications  applications on end systems allows for rapid app development, propagation application transport network data link physical application transport network data link physical application transport network data link physical H. Fauconnier

6 M2-Internet 6 Chapter 3: Application layer r 2.1 Principles of network applications r 2.2 Web and HTTP r 2.3 FTP r 2.4 Electronic Mail  SMTP, POP3, IMAP r 2.5 DNS r 2.6 P2P applications H. Fauconnier

7 M2-Internet 7 Application architectures r Client-server  Including data centers / cloud computing r Peer-to-peer (P2P) r Hybrid of client-server and P2P H. Fauconnier

8 M2-Internet 8 Client-server architecture server:  always-on host  permanent IP address  server farms for scaling clients:  communicate with server  may be intermittently connected  may have dynamic IP addresses  do not communicate directly with each other client/server H. Fauconnier

9 Google Data Centers r Estimated cost of data center: $600M r Google spent $2.4B in 2007 on new data centers r Each data center uses 50-100 megawatts of power H. Fauconnier9 M2-Internet

10 10 Pure P2P architecture r no always-on server r arbitrary end systems directly communicate r peers are intermittently connected and change IP addresses Highly scalable but difficult to manage peer-peer H. Fauconnier

11 M2-Internet 11 Hybrid of client-server and P2P Skype  voice-over-IP P2P application  centralized server: finding address of remote party:  client-client connection: direct (not through server) Instant messaging  chatting between two users is P2P  centralized service: client presence detection/location user registers its IP address with central server when it comes online user contacts central server to find IP addresses of buddies H. Fauconnier

12 M2-Internet 12 Processes communicating Process: program running within a host. r within same host, two processes communicate using inter-process communication (defined by OS). r processes in different hosts communicate by exchanging messages Client process: process that initiates communication Server process: process that waits to be contacted rNote: applications with P2P architectures have client processes & server processes H. Fauconnier

13 M2-Internet 13 Sockets r process sends/receives messages to/from its socket r socket analogous to door  sending process shoves message out door  sending process relies on transport infrastructure on other side of door which brings message to socket at receiving process process TCP with buffers, variables socket host or server process TCP with buffers, variables socket host or server Internet controlled by OS controlled by app developer rAPI: (1) choice of transport protocol; (2) ability to fix a few parameters (lots more on this later) H. Fauconnier

14 M2-Internet 14 Addressing processes r to receive messages, process must have identifier r host device has unique 32-bit IP address  Exercise: use ipconfig from command prompt to get your IP address (Windows) r Q: does IP address of host on which process runs suffice for identifying the process?  A: No, many processes can be running on same r Identifier includes both IP address and port numbers associated with process on host. r Example port numbers:  HTTP server: 80  Mail server: 25 H. Fauconnier

15 M2-Internet 15 App-layer protocol defines r Types of messages exchanged,  e.g., request, response r Message syntax:  what fields in messages & how fields are delineated r Message semantics  meaning of information in fields r Rules for when and how processes send & respond to messages Public-domain protocols: r defined in RFCs r allows for interoperability r e.g., HTTP, SMTP, BitTorrent Proprietary protocols: r e.g., Skype, ppstream H. Fauconnier

16 M2-Internet 16 What transport service does an app need? Data loss r some apps (e.g., audio) can tolerate some loss r other apps (e.g., file transfer, telnet) require 100% reliable data transfer Timing r some apps (e.g., Internet telephony, interactive games) require low delay to be “effective” Throughput rsome apps (e.g., multimedia) require minimum amount of throughput to be “effective” rother apps (“elastic apps”) make use of whatever throughput they get Security  Encryption, data integrity, … H. Fauconnier

17 M2-Internet 17 Transport service requirements of common apps Application file transfer e-mail Web documents real-time audio/video stored audio/video interactive games instant messaging Data loss no loss loss-tolerant no loss Throughput elastic audio: 5kbps-1Mbps video:10kbps-5Mbps same as above few kbps up elastic Time Sensitive no yes, 100’s msec yes, few secs yes, 100’s msec yes and no H. Fauconnier

18 M2-Internet 18 Internet transport protocols services TCP service: r connection-oriented: setup required between client and server processes r reliable transport between sending and receiving process r flow control: sender won’t overwhelm receiver r congestion control: throttle sender when network overloaded r does not provide: timing, minimum throughput guarantees, security UDP service: r unreliable data transfer between sending and receiving process r does not provide: connection setup, reliability, flow control, congestion control, timing, throughput guarantee, or security Q: why bother? Why is there a UDP? H. Fauconnier

19 M2-Internet 19 Internet apps: application, transport protocols Application e-mail remote terminal access Web file transfer streaming multimedia Internet telephony Application layer protocol SMTP [RFC 2821] Telnet [RFC 854] HTTP [RFC 2616] FTP [RFC 959] HTTP (eg Youtube), RTP [RFC 1889] SIP, RTP, proprietary (e.g., Skype) Underlying transport protocol TCP TCP or UDP typically UDP H. Fauconnier

20 M2-Internet 20 Chapter 2: Application layer r 2.1 Principles of network applications r 2.2 Web and HTTP r 2.3 FTP r 2.4 Electronic Mail  SMTP, POP3, IMAP r 2.5 DNS r 2.6 P2P applications r 2.7 Socket programming with UDP r 2.8 Socket programming with TCP H. Fauconnier

21 M2-Internet 21 Web and HTTP First some jargon r Web page consists of objects r Object can be HTML file, JPEG image, Java applet, audio file,… r Web page consists of base HTML-file which includes several referenced objects r Each object is addressable by a URL r Example URL: www.someschool.edu/someDept/pic.gif host name path name H. Fauconnier

22 M2-Internet 22 HTTP overview HTTP: hypertext transfer protocol r Web’s application layer protocol r client/server model  client: browser that requests, receives, “displays” Web objects  server: Web server sends objects in response to requests PC running Explorer Server running Apache Web server Mac running Navigator HTTP request HTTP response H. Fauconnier

23 M2-Internet 23 HTTP overview (continued) Uses TCP: r client initiates TCP connection (creates socket) to server, port 80 r server accepts TCP connection from client r HTTP messages (application- layer protocol messages) exchanged between browser (HTTP client) and Web server (HTTP server) r TCP connection closed HTTP is “stateless” r server maintains no information about past client requests Protocols that maintain “state” are complex! rpast history (state) must be maintained rif server/client crashes, their views of “state” may be inconsistent, must be reconciled aside H. Fauconnier

24 M2-Internet 24 HTTP connections Nonpersistent HTTP r At most one object is sent over a TCP connection. Persistent HTTP r Multiple objects can be sent over single TCP connection between client and server. H. Fauconnier

25 M2-Internet 25 Nonpersistent HTTP Suppose user enters URL www.someSchool.edu/someDepartment/home.index 1a. HTTP client initiates TCP connection to HTTP server (process) at www.someSchool.edu on port 80 2. HTTP client sends HTTP request message (containing URL) into TCP connection socket. Message indicates that client wants object someDepartment/home.index 1b. HTTP server at host www.someSchool.edu waiting for TCP connection at port 80. “accepts” connection, notifying client 3. HTTP server receives request message, forms response message containing requested object, and sends message into its socket time (contains text, references to 10 jpeg images) H. Fauconnier

26 M2-Internet 26 Nonpersistent HTTP (cont.) 5. HTTP client receives response message containing html file, displays html. Parsing html file, finds 10 referenced jpeg objects 6. Steps 1-5 repeated for each of 10 jpeg objects 4. HTTP server closes TCP connection. time H. Fauconnier

27 M2-Internet 27 Non-Persistent HTTP: Response time Definition of RTT: time for a small packet to travel from client to server and back. Response time: r one RTT to initiate TCP connection r one RTT for HTTP request and first few bytes of HTTP response to return r file transmission time total = 2RTT+transmit time time to transmit file initiate TCP connection RTT request file RTT file received time H. Fauconnier

28 M2-Internet 28 Persistent HTTP Nonpersistent HTTP issues: r requires 2 RTTs per object r OS overhead for each TCP connection r browsers often open parallel TCP connections to fetch referenced objects Persistent HTTP r server leaves connection open after sending response r subsequent HTTP messages between same client/server sent over open connection r client sends requests as soon as it encounters a referenced object r as little as one RTT for all the referenced objects H. Fauconnier

29 M2-Internet 29 HTTP request message r two types of HTTP messages: request, response r HTTP request message:  ASCII (human-readable format) GET /somedir/page.html HTTP/1.1 Host: www.someschool.edu User-agent: Mozilla/4.0 Connection: close Accept-language:fr (extra carriage return, line feed) request line (GET, POST, HEAD commands) header lines Carriage return, line feed indicates end of message H. Fauconnier

30 M2-Internet 30 HTTP request message: general format H. Fauconnier

31 M2-Internet 31 Uploading form input Post method: r Web page often includes form input r Input is uploaded to server in entity body URL method: r Uses GET method r Input is uploaded in URL field of request line: www.somesite.com/animalsearch?monkeys&banana H. Fauconnier

32 M2-Internet 32 Method types HTTP/1.0 r GET r POST r HEAD  asks server to leave requested object out of response HTTP/1.1 r GET, POST, HEAD r PUT  uploads file in entity body to path specified in URL field r DELETE  deletes file specified in the URL field H. Fauconnier

33 M2-Internet 33 POST r dans une requête POST les données sont dans le corps du message r les données définissent des variables qui seront utilisées par le CGI r l'url requise est normalement un programme r la réponse HTTP est normalement la sortie d'un programme H. Fauconnier

34 M2-Internet 34 HTTP response message HTTP/1.1 200 OK Connection close Date: Thu, 06 Aug 1998 12:00:15 GMT Server: Apache/1.3.0 (Unix) Last-Modified: Mon, 22 Jun 1998 …... Content-Length: 6821 Content-Type: text/html data data data data data... status line (protocol status code status phrase) header lines data, e.g., requested HTML file H. Fauconnier

35 M2-Internet 35 HTTP response status codes 200 OK  request succeeded, requested object later in this message 301 Moved Permanently  requested object moved, new location specified later in this message (Location:) 400 Bad Request  request message not understood by server 404 Not Found  requested document not found on this server 505 HTTP Version Not Supported In first line in server->client response message. A few sample codes: H. Fauconnier

36 M2-Internet 36 Trying out HTTP (client side) for yourself 1. Telnet to your favorite Web server: Opens TCP connection to port 80 (default HTTP server port) at cis.poly.edu. Anything typed in sent to port 80 at cis.poly.edu telnet cis.poly.edu 80 2. Type in a GET HTTP request: GET /~ross/ HTTP/1.1 Host: cis.poly.edu By typing this in (hit carriage return twice), you send this minimal (but complete) GET request to HTTP server 3. Look at response message sent by HTTP server! H. Fauconnier

37 M2-Internet 37 Méthodes http r GET  C'est la méthode la plus courante pour demander une ressource. Une requête GET est sans effet sur la ressource, il doit être possible de répéter la requête sans effet. r HEAD  Cette méthode ne demande que des informations sur la ressource, sans demander la ressource elle-même. r POST  Cette méthode doit être utilisée lorsqu'une requête modifie la ressource. r OPTIONS  Cette méthode permet d'obtenir les options de communication d'une ressource ou du serveur en général. r CONNECT  Cette méthode permet d'utiliser un proxy comme un tunnel de communication. r TRACE  Cette méthode demande au serveur de retourner ce qu'il a reçu, dans le but de tester et effectuer un diagnostic sur la connexion. r PUT  Cette méthode permet d'ajouter une ressource sur le serveur. r DELETE  Cette méthode permet de supprimer une ressource du serveur. H. Fauconnier

38 M2-Internet 38 entêtes r Host  Permet de préciser le site Web concerné par la requête, ce qui est nécessaire pour un serveur hébergeant plusieurs sites à la même adresse IP (name based virtual host, hôte virtuel basé sur le nom). (Obligatoire) r Referer  Indique l'URI du document qui a donné un lien sur la ressource demandée. Cet en- tête permet aux webmasters d'observer d'où viennent les visiteurs. r User-Agent  Indique le logiciel utilisé pour se connecter. Il s'agit généralement d'un navigateur Web ou d'un robot d'indexation. r Connection  connection persistante ou non r Accept  Cet en-tête liste les types MIME de contenu acceptés par le client. Le caractère étoile * peut servir à spécifier tous les types / sous-types. r Accept-Charset  Spécifie les encodages de caractères acceptés. r Accept-Language  Spécifie les langues acceptés. H. Fauconnier

39 M2-Internet 39 Réponses r Date  Moment auquel le message est généré. r Server  Indique quel modèle de serveur HTTP répond à la requête. r Content-Length  Indique la taille en octets de la ressource. r Content-Type  Indique le type MIME de la ressource. r Expires  Indique le moment après lequel la ressource devrait être considérée obsolète ; permet aux navigateurs Web de déterminer jusqu'à quand garder la ressource en mémoire cache. r Last-Modified  Indique la date de dernière modification de la ressource demandée. H. Fauconnier

40 M2-Internet 40 User-server state: cookies Many major Web sites use cookies Four components: 1) cookie header line of HTTP response message 2) cookie header line in HTTP request message 3) cookie file kept on user’s host, managed by user’s browser 4) back-end database at Web site Example:  Susan access Internet always from same PC  She visits a specific e- commerce site for first time  When initial HTTP requests arrives at site, site creates a unique ID and creates an entry in backend database for ID H. Fauconnier

41 M2-Internet 41 Cookies: keeping “state” (cont.) client server usual http request msg usual http response + Set-cookie: 1678 usual http request msg cookie: 1678 usual http response msg usual http request msg cookie: 1678 usual http response msg cookie- specific action cookie- spectific action server creates ID 1678 for user entry in backend database access Cookie file amazon: 1678 ebay: 8734 Cookie file ebay: 8734 Cookie file amazon: 1678 ebay: 8734 one week later: H. Fauconnier

42 M2-Internet 42 Cookies (continued) What cookies can bring: r authorization r shopping carts r recommendations r user session state (Web e-mail) Cookies and privacy: rcookies permit sites to learn a lot about you ryou may supply name and e- mail to sites rsearch engines use redirection & cookies to learn yet more radvertising companies obtain info across sites aside H. Fauconnier

43 M2-Internet 43 Web caches (proxy server) r user sets browser: Web accesses via cache r browser sends all HTTP requests to cache  object in cache: cache returns object  else cache requests object from origin server, then returns object to client Goal: satisfy client request without involving origin server client Proxy server client HTTP request HTTP response HTTP request HTTP response origin server origin server H. Fauconnier

44 M2-Internet 44 More about Web caching r Cache acts as both client and server r Typically cache is installed by ISP (university, company, residential ISP) Why Web caching? r Reduce response time for client request. r Reduce traffic on an institution’s access link. r Internet dense with caches enables “poor” content providers to effectively deliver content (but so does P2P file sharing) H. Fauconnier

45 M2-Internet 45 Caching example Assumptions r average object size = 100,000 bits r avg. request rate from institution’s browsers to origin servers = 15/sec r delay from institutional router to any origin server and back to router = 2 sec Consequences r utilization on LAN = 15% r utilization on access link = 100% r total delay = Internet delay + access delay + LAN delay = 2 sec + minutes + milliseconds origin servers public Internet institutional network 10 Mbps LAN 1.5 Mbps access link institutional cache H. Fauconnier

46 M2-Internet 46 Caching example (cont) Possible solution r increase bandwidth of access link to, say, 10 Mbps Consequences r utilization on LAN = 15% r utilization on access link = 15% r Total delay = Internet delay + access delay + LAN delay = 2 sec + msecs + msecs r often a costly upgrade origin servers public Internet institutional network 10 Mbps LAN 10 Mbps access link institutional cache H. Fauconnier

47 M2-Internet 47 Caching example (cont) Install cache r suppose hit rate is.4 Consequence r 40% requests will be satisfied almost immediately r 60% requests satisfied by origin server r utilization of access link reduced to 60%, resulting in negligible delays (say 10 msec) r total avg delay = Internet delay + access delay + LAN delay =.6*(2.01) secs + milliseconds < 1.4 secs origin servers public Internet institutional network 10 Mbps LAN 1.5 Mbps access link institutional cache H. Fauconnier

48 M2-Internet 48 Conditional GET r Goal: don’t send object if cache has up-to-date cached version r cache: specify date of cached copy in HTTP request If-modified-since: r server: response contains no object if cached copy is up- to-date: HTTP/1.0 304 Not Modified cache server HTTP request msg If-modified-since: HTTP response HTTP/1.0 304 Not Modified object not modified HTTP request msg If-modified-since: HTTP response HTTP/1.0 200 OK object modified H. Fauconnier

49 Préliminaire r http est un protocole qui définit des formats pour les interactions entre serveurs et clients r Du côté du client: les navigateurs r Du côté serveur: des serveurs http  Apache (httpd), IIS (internet information service) microsoft, Zeux etc…  Mais aussi des serveurs d'application comme glassfish ou tomcat M2-Internet 49 H. Fauconnier

50 apache r Pour pouvoir tester les exemples on utilisera apache  logiciel libre disponible sur la plupart des plateformes  Le serveur le plus fréquent  Prise en charge de nombreux modules, (perl php, python, ruby…) cgi  Serveurs virtuels M2-Internet 1-50 H. Fauconnier

51 Principes… r Le serveur reçoit des requêtes http et renvoie des pages html dans des réponses http  Interpréter les requêtes  Lancer sur le côté serveur les applications concernées  Récupérer les résultats et les transmettre au client r Configuration: httpd.conf (en général dans /etc (et par catalogue.htaccess) M2-Internet 1-51 H. Fauconnier

52 Principes r Correspondance entre url et fichiers locaux  DocumentRoot: DocumentRoot: /var/www/html http://www.exemple.com/un/deux.html sera /var/www/html/un/deux.html  Pages des uitlisateurs UserDir: www http://www.example.com/~user/file.html sera /home/user/public_html/file.html  En plus des alias et des redirections M2-Internet 1-52 H. Fauconnier

53 Pour voir… r Sur cette machine:  /private/etc/apache2/httpd.conf /private/etc/apache2/httpd.conf  UserDir: Site M2-Internet 1-53 H. Fauconnier

54 M2-Internet 54 CGI r Common Gateway Interface r exécuter du code du côté serveur r Passage de paramètre par la méthode POST ou la méthode GET r Variables d'environnement H. Fauconnier

55 Pour Apache r Les executables cgi  ScriptAlias /cgi-bin/ /usr/local/apache2/cgi-bin/  Pour http://www.example.com/cgi-bin/test.pl  /usr/local/apache2/cgi-bin/test.pl sera exécuté r "Paramètres"  POST: transmis sur l'entrée standard (STDIN)  GET: variable de l'environnement QUERY_STRING r STDOUT pour la réponse  (au moins un MIME type header Content-type: text/htmlet deux newline) M2-Internet 55 H. Fauconnier

56 M2-Internet 56 Exemple r en shell: date.cgi #!/bin/sh tmp=`/bin/date` echo "Content-type: text/html\n Script Cgi La date courante sur le serveur est $tmp " l'URL affichera la date http://localhost/cgi-bin/date.cgi H. Fauconnier

57 M2-Internet 57 Avec un formulaire:formulaire Formulaire simple Répondez aux questions suivantes Prénom : Nom : Age : - de 18 ans 19 à 40 ans 41 à 60 ans + de 60 ans <INPUT TYPE=reset VALUE="Remettre à zéro"> http://localhost/~hf/formulaire.html H. Fauconnier

58 M2-Internet 58 Résultat r par la méthode get codage des paramètres: r prenom=Hugues&nom=Fauconnier&age= 41+%E0+60+ans  le navigateur génère l'url: http://www.monsite.com/cgi- bin/treat.pl?prenom=Hugues&nom=Fauconnier&age=41+ %E0+60+ans r Avec la méthode POST http://www.monsite.com/cgi-bin/treat.pl prenom=Hugues&nom=Fauconnier&age=41 H. Fauconnier

59 M2-Internet 59 Traitement en perl r fichier perl fichier perl H. Fauconnier

60 M2-Internet 60 Paramètres r Les paramètres sont accessibles par l'intermédiaire de la variable d'environnement QUERY_STRING H. Fauconnier

61 M2-Internet 61 Variables d'environnement r SERVER_SOFTWARE  Le nom et la version du serveur HTTP répondant à la requête. (Format : nom/version) r SERVER_NAME  Le nom d'hôte, alias DNS ou adresse IP du serveur. r GATEWAY_INTERFACE  La révision de la spécification CGI que le serveur utilise. (Format : CGI/révision) H. Fauconnier

62 M2-Internet 62 Variables… r SERVER_PROTOCOL  Le nom et la révision du protocole dans lequel la requête a été faite (Format : protocole/révision) r SERVER_PORT  Le numéro de port sur lequel la requête a été envoyée. r REQUEST_METHOD  La méthode utilisée pour faire la requête. Pour HTTP, elle contient généralement « GET » ou « POST ». r PATH_INFO  Le chemin supplémentaire du script tel que donné par le client. Par exemple, si le serveur héberge le script « /cgi- bin/monscript.cgi » et que le client demande l'url « http://serveur.org/cgi-bin/monscript.cgi/marecherche », alors PATH_INFO contiendra « marecherche ». r PATH_TRANSLATED  Contient le chemin demandé par le client après que les conversions virtuel → physique aient été faites par le serveur. H. Fauconnier

63 M2-Internet 63 Variables r SCRIPT_NAME  Le chemin virtuel vers le script étant exécuté. Exemple : « /cgi- bin/script.cgi » r QUERY_STRING  Contient tout ce qui suit le « ? » dans l'URL envoyée par le client. Toutes les variables provenant d'un formulaire envoyé avec la méthode « GET » sera contenue dans le QUERY_STRING sous la forme « var1=val1&var2=val2&... ». r REMOTE_HOST  Le nom d'hôte du client. Si le serveur ne possède pas cette information (par exemple, lorsque la résolution DNS inverse est désactivée), REMOTE_HOST sera vide. r REMOTE_ADDR  L'adresse IP du client. r AUTH_TYPE  Le type d'identification utilisé pour protéger le script (s’il est protégé et si le serveur supporte l'identification). H. Fauconnier

64 M2-Internet 64 Variables r AUTH_TYPE  Le type d'identification utilisé pour protéger le script (s’il est protégé et si le serveur supporte l'identification). r REMOTE_USER  Le nom d'utilisateur du client, si le script est protégé et si le serveur supporte l'identification. r REMOTE_IDENT  Nom d'utilisateur (distant) du client faisant la requête. Le serveur doit supporter l'identification RFC 931. Cette variable devraient être utilisée à des fins de journaux seulement. r CONTENT_TYPE  Le type de contenu attaché à la requête, si des données sont attachées (comme lorsqu'un formulaire est envoyé avec la méthode « POST »). r CONTENT_LENGTH  La longueur du contenu envoyé par le client. H. Fauconnier

65 M2-Internet 65 Variables r HTTP_ACCEPT Les types de données MIME que le client accepte de recevoir. Exemple : text/*, image/jpeg, image/png, image/*, */* r HTTP_ACCEPT_LANGUAGE Les langages dans lequel le client accepte de recevoir la réponse. Exemple : fr_CA, fr r HTTP_USER_AGENT Le navigateur utilisé par le client. Exemple : Mozilla/5.0 (compatible; Konqueror/3; Linux) H. Fauconnier

66 M2-Internet 66 Compléments: Javascript r Code qui s'exécute du côté du client  calcul local  contrôle d'une zone de saisie  affichage d'alerte  fenêtres menus etc.. r Balise : le code... H. Fauconnier

67 M2-Internet 67 Exemple: bonjourbonjour Très facile function bonjour() { alert ("Bonjour madame, bonjour monsieur"); } Bonjour http://localhost/~hf/BjrJvs.html H. Fauconnier

68 M2-Internet 68 Un peu plus: minicalcul (source)minicalculsource Petit calcul Calcul Un petit exemple de formulaire. Création d'une fenêtre avec JavaScript H. Fauconnier

69 M2-Internet 69 Suite Argument 1 * Argument 2 <INPUT TYPE='TEXT' SIZE=20 NAME='arg2' onChange='calcul();'> Résultat= <INPUT TYPE='TEXT' SIZE=20 NAME='res' > <INPUT TYPE='RESET' VALUE='Effacer tout' onClick=' if (!confirm("Vraiment vous voulez effacer ?")) exit;'> http://localhost/~hf/Simul.html H. Fauconnier

70 M2-Internet 70 Fichiers js r Ctrl.js calcul Ctrl.jscalcul function ctrl() { if (isNaN(window.document.Simul.res.value )) { alert ("Valeur incorrecte : " + document.Simul.res.value + "?"); document.forms[0].res.focus(); } function calcul() { v1=document.forms[0].arg1.value; v2=document.forms[0].arg2.value; document.forms[0].res.value = v2*v1 ; } H. Fauconnier

71 M2-Internet 71 suite et fin r exemples/fenetre.js exemples/fenetre.js function afficheDoc() { options = "width=300,height=200"; fenetre = window.open('','MU',options); fenetre.document.open(); manuel = " Documentation " + " " + "Il n'y a pas besoin d'aide " + " c'est facile." + " Bonne chance ! "; fenetre.document.write(manuel); fenetre.document.close(); } H. Fauconnier

72 M2-Internet 72 Compléments: php r php est un langage de script pour les serveurs webs r de nombreuses fonctions permettent de traiter les requêtes http (en particulier des requêtes concernant des bases de données) r ici on est du côté du serveur… H. Fauconnier

73 M2-Internet 73 Exemple simplesimple Exemple très simple Exemple le <?php echo "Client :". $_SERVER['HTTP_USER_AGENT']. " "; echo "Adresse IP client:".$_SERVER['REMOTE_ADDR']." "; echo "Server: ". $_SERVER['SERVER_NAME']; ?> http://localhost/~hf/ExempleSimple.php H. Fauconnier

74 M2-Internet 74 Résultat Exemple le 8/11/2006 à 15:54:29 Client :Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1;.NET CLR 1.1.4322; InfoPath.1) Adresse IP client:127.0.0.1 Server: localhost H. Fauconnier

75 M2-Internet 75 Reçu par le client Exemple très simple Exemple le 8/11/2006 à 15:54:29 Client :Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1;.NET CLR 1.1.4322; InfoPath.1) Adresse IP client:127.0.0.1 Server: localhost H. Fauconnier

76 M2-Internet 76 Php r On est ici côté serveur:  les balises sont interprétées par le serveur (apache par exemple) et servent à générer la page html reçue par le client r Mais surtout php permet  d'accéder aux variables d'environnement  d'utiliser de nombreuses fonctionnalités sessions, paramètres etc. r Php sert souvent d'interface pour MySql serveur simple de bases de données H. Fauconnier

77 M2-Internet 77 Php r pas de typage ni de déclaration des variables r $v est remplacé par la valeur de v (et permet aussi l'affectation) r echo "$v"; r constantes define("PI, 3.1415); r types des variables  numériques $i=1; $v=3.14;  chaînes de caractères (expressions régulières) $nom="Hugues"; ',",{} H. Fauconnier

78 php r Variables  Locales (à une fonction)  Globales  Super globales (disponibles dans tout contexte)  Static (garde sa valeur)  Variables dynamiques (le nom de la variable est une variable) $a='bonjour' $$a='monde' echo "$a ${$a}" echo "$a $bonjour" M2-Internet 78 H. Fauconnier

79 M2-Internet 79 php r tableaux  indicés $tab[0]="un"; $tab=array("un","deux","trois");  associatifs $m=array("un"=>"one", "deux"=>"two"); $m["trois"]="three";  next() prev() key() current do {echo "Clé=key($m).Valeur= current($m)"} while(next($mes)); foreach($m as $cle =>$val) {echo "Clé=$cle.Valeur=$val";} H. Fauconnier

80 php r Mais aussi (php4 et php5)  Programmation orientée objets Classes et Objets Liaison dynamique Constructeurs …  Exceptions M2-Internet 80 H. Fauconnier

81 M2-Internet 81 Php r structures de contrôles  if  if else  while  do while  for  foreach break, continue H. Fauconnier

82 M2-Internet 82 fonctions function Nom([$arg1, $arg2,...]) { corps } passage par valeur (et par référence &) exemples function Add($i,$j){ $somme= $i + $j; return $somme; } function Add($i,$j,&$somme){ $somme= $i + $j; } H. Fauconnier

83 M2-Internet 83 Pour le serveur… r tableaux associatifs prédéfinis  $_SERVER: environnement serveur REQUEST_METHOD QUERY_STRING CONTENT_LENGTH SERVER_NAME PATH_INFO HTTP_USER_AGENT REMOTE_ADDR REMOTE_HOST REMOTE_USER REMOTE_PASSWORD H. Fauconnier

84 M2-Internet 84 Suite r Autres tableaux  $_ENV: environnement système  $_COOKIE  $_GET  $_POST  $_FILES  $_REQUEST (variables des 4 précédents)  $_SESSION  $GLOBALS les variables globales du script H. Fauconnier

85 M2-Internet 85 Cookies et php <?php // Est-ce que le Cookie existe ? if (isSet($_COOKIE['compteur'])) { $message = "Vous êtes déjà venu {$_COOKIE['compteur']} fois ". "me rendre visite \n"; // On incrémente le compteur $valeur = $_COOKIE['compteur'] + 1; } else { // Il faut créer le cookie avec la valeur 1 $message = "Bonjour, je vous envoie un cookie \n"; $valeur = 1; } // Envoi du cookie SetCookie ("compteur", $valeur); ?> H. Fauconnier

86 M2-Internet 86 Cookies et php (fin) Les cookies Un compteur d'accès au site avec cookie http://localhost/~hf/SetCookie.php H. Fauconnier

87 M2-Internet 87 En utilisant les sessions <?php // La fonction session_start fait tout le travail session_start(); ?> Les cookies Un compteur d'accès au site avec Session H. Fauconnier

88 M2-Internet 88 Fin <?php if (!isSet($_SESSION['cp'])) { $_SESSION['cp']=1; echo "C'estlapremière fois,votre id est:". session_id()." "; } else{ $_SESSION['cp']++; echo "C'est votre ".$_SESSION['cp']." n-ième connexion"; if($_SESSION['cp']>10){ echo "on vous a trop vu"." "; session_destroy(); } ?> http://localhost/~hf/SessionPHP.php H. Fauconnier

89 M2-Internet 89 session r session_start() r session_destroy() r session_id()  on peut associer des variables à la session par le tableau associatif $_SESSION  elle sera accessible à chaque session_start() jusqu'au session_destroy() pour toute connexion qui fournit le session_id(). H. Fauconnier

90 M2-Internet 90 Chapter 2: Application layer r 2.1 Principles of network applications r 2.2 Web and HTTP r 2.3 FTP r 2.4 Electronic Mail  SMTP, POP3, IMAP r 2.5 DNS r 2.6 P2P applications r 2.7 Socket programming with UDP r 2.8 Socket programming with TCP H. Fauconnier

91 M2-Internet 91 FTP: the file transfer protocol r transfer file to/from remote host r client/server model  client: side that initiates transfer (either to/from remote)  server: remote host r ftp: RFC 959 r ftp server: port 21 file transfer FTP server FTP user interface FTP client local file system remote file system user at host H. Fauconnier

92 M2-Internet 92 FTP: separate control, data connections r FTP client contacts FTP server at port 21, TCP is transport protocol r client authorized over control connection r client browses remote directory by sending commands over control connection. r when server receives file transfer command, server opens 2 nd TCP connection (for file) to client r after transferring one file, server closes data connection. FTP client FTP server TCP control connection port 21 TCP data connection port 20 rserver opens another TCP data connection to transfer another file. rcontrol connection: “out of band” rFTP server maintains “state”: current directory, earlier authentication H. Fauconnier

93 M2-Internet 93 FTP commands, responses Sample commands: r sent as ASCII text over control channel  USER username  PASS password  LIST return list of file in current directory  RETR filename retrieves (gets) file  STOR filename stores (puts) file onto remote host Sample return codes r status code and phrase (as in HTTP) r 331 Username OK, password required r 125 data connection already open; transfer starting r 425 Can’t open data connection r 452 Error writing file H. Fauconnier

94 M2-Internet 94 Chapter 2: Application layer r 2.1 Principles of network applications r 2.2 Web and HTTP r 2.3 FTP r 2.4 Electronic Mail  SMTP, POP3, IMAP r 2.5 DNS r 2.6 P2P applications r 2.7 Socket programming with UDP r 2.8 Socket programming with TCP H. Fauconnier

95 M2-Internet 95 Electronic Mail Three major components: r user agents r mail servers r simple mail transfer protocol: SMTP User Agent r a.k.a. “mail reader” r composing, editing, reading mail messages r e.g., Eudora, Outlook, elm, Mozilla Thunderbird r outgoing, incoming messages stored on server user mailbox outgoing message queue mail server user agent user agent user agent mail server user agent user agent mail server user agent SMTP H. Fauconnier

96 M2-Internet 96 Electronic Mail: mail servers Mail Servers r mailbox contains incoming messages for user r message queue of outgoing (to be sent) mail messages r SMTP protocol between mail servers to send email messages  client: sending mail server  “server”: receiving mail server mail server user agent user agent user agent mail server user agent user agent mail server user agent SMTP H. Fauconnier

97 M2-Internet 97 Electronic Mail: SMTP [RFC 2821] r uses TCP to reliably transfer email message from client to server, port 25 r direct transfer: sending server to receiving server r three phases of transfer  handshaking (greeting)  transfer of messages  closure r command/response interaction  commands: ASCII text  response: status code and phrase r messages must be in 7-bit ASCII H. Fauconnier

98 M2-Internet 98 Scenario: Alice sends message to Bob 1) Alice uses UA to compose message and “to” bob@someschool.edu 2) Alice’s UA sends message to her mail server; message placed in message queue 3) Client side of SMTP opens TCP connection with Bob’s mail server 4) SMTP client sends Alice’s message over the TCP connection 5) Bob’s mail server places the message in Bob’s mailbox 6) Bob invokes his user agent to read message user agent mail server mail server user agent 1 2 3 4 5 6 H. Fauconnier

99 M2-Internet 99 Sample SMTP interaction S: 220 hamburger.edu C: HELO crepes.fr S: 250 Hello crepes.fr, pleased to meet you C: MAIL FROM: S: 250 alice@crepes.fr... Sender ok C: RCPT TO: S: 250 bob@hamburger.edu... Recipient ok C: DATA S: 354 Enter mail, end with "." on a line by itself C: Do you like ketchup? C: How about pickles? C:. S: 250 Message accepted for delivery C: QUIT S: 221 hamburger.edu closing connection H. Fauconnier

100 M2-Internet 100 Try SMTP interaction for yourself:  telnet servername 25 r see 220 reply from server r enter HELO, MAIL FROM, RCPT TO, DATA, QUIT commands above lets you send email without using email client (reader) H. Fauconnier

101 M2-Internet 101 SMTP: final words r SMTP uses persistent connections r SMTP requires message (header & body) to be in 7- bit ASCII  SMTP server uses CRLF.CRLF to determine end of message Comparison with HTTP: r HTTP: pull r SMTP: push r both have ASCII command/response interaction, status codes r HTTP: each object encapsulated in its own response msg r SMTP: multiple objects sent in multipart msg H. Fauconnier

102 M2-Internet 102 Mail message format SMTP: protocol for exchanging email msgs RFC 822: standard for text message format: r header lines, e.g.,  To:  From:  Subject: different from SMTP commands! r body  the “message”, ASCII characters only header body blank line H. Fauconnier

103 M2-Internet 103 Message format: multimedia extensions r MIME: multimedia mail extension, RFC 2045, 2056 r additional lines in msg header declare MIME content type From: alice@crepes.fr To: bob@hamburger.edu Subject: Picture of yummy crepe. MIME-Version: 1.0 Content-Transfer-Encoding: base64 Content-Type: image/jpeg base64 encoded data....................................base64 encoded data multimedia data type, subtype, parameter declaration method used to encode data MIME version encoded data H. Fauconnier

104 M2-Internet 104 MIME r Multipurpose Internet Mail Extensions  texte en caractères non US ASCII  attachements  messages en plusieurs parties  défini dans l'entête du mail  à l'origine pour le mail uniquement mais utilisé de plus en plus fréquemment (exemple HTTP) r SMTP ne considère que des caractères ASCII 7 bits d'où la nécessité de codage décodage H. Fauconnier

105 M2-Internet 105 MIME r Un message peut être en plusieurs parties (multipart) définies par l'entête "Content- Type"  exemple Content-Type: text/plain L'entête d'un message peut contenir autre chose que du US ASCII (par exemple dans le champ SUBJECT: "=?charset?encoding?encoded text?=". Subject: =?utf-8?Q?=C2=A1Hola,_se=C3=B1or!?= (Subject: ¡Hola, señor!) H. Fauconnier

106 M2-Internet 106 MIME r Exemple de multipart Message: Content-type: multipart/mixed; boundary="frontier" MIME-version: 1.0 This is a multi-part message in MIME format. --frontier Content-type: text/plain This is the body of the message. --frontier Content-type: application/octet-stream Content-transfer-encoding: base64 PGh0bWw+CiAgPGhlYWQ+CiAgPC9oZWFkPgogIDxib2R5Pgo gICAgAVGhpcyBpcyB0aGUgYm9keSBvZiB0aGUgbWVzc2FnZ S48L3A+CiAgPC9ib2R5Pgo8L2h0bWw+Cg== --frontier-- H. Fauconnier

107 M2-Internet 107 Mail access protocols r SMTP: delivery/storage to receiver’s server r Mail access protocol: retrieval from server  POP: Post Office Protocol [RFC 1939] authorization (agent server) and download  IMAP: Internet Mail Access Protocol [RFC 1730] more features (more complex) manipulation of stored msgs on server  HTTP: gmail, Hotmail, Yahoo! Mail, etc. user agent sender’s mail server user agent SMTP access protocol receiver’s mail server H. Fauconnier

108 M2-Internet 108 POP3 protocol authorization phase r client commands:  user: declare username  pass: password r server responses  +OK  -ERR transaction phase, client:  list: list message numbers  retr: retrieve message by number  dele: delete r quit C: list S: 1 498 S: 2 912 S:. C: retr 1 S: S:. C: dele 1 C: retr 2 S: S:. C: dele 2 C: quit S: +OK POP3 server signing off S: +OK POP3 server ready C: user bob S: +OK C: pass hungry S: +OK user successfully logged on H. Fauconnier

109 M2-Internet 109 POP3 (more) and IMAP More about POP3 r Previous example uses “download and delete” mode. r Bob cannot re-read e- mail if he changes client r “Download-and-keep”: copies of messages on different clients r POP3 is stateless across sessions IMAP r Keep all messages in one place: the server r Allows user to organize messages in folders r IMAP keeps user state across sessions:  names of folders and mappings between message IDs and folder name H. Fauconnier

110 M2-Internet 110 Chapter 2: Application layer r 2.1 Principles of network applications r 2.2 Web and HTTP r 2.3 FTP r 2.4 Electronic Mail  SMTP, POP3, IMAP r 2.5 DNS r 2.6 P2P applications r 2.7 Socket programming with UDP r 2.8 Socket programming with TCP H. Fauconnier

111 M2-Internet 111 DNS: Domain Name System People: many identifiers:  SSN, name, passport # Internet hosts, routers:  IP address (32 bit) - used for addressing datagrams  “name”, e.g., ww.yahoo.com - used by humans Q: map between IP addresses and name ? Domain Name System: r distributed database implemented in hierarchy of many name servers r application-layer protocol host, routers, name servers to communicate to resolve names (address/name translation)  note: core Internet function, implemented as application-layer protocol  complexity at network’s “edge” H. Fauconnier