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Network Programming

Network Programming. By J. H. Wang Nov. 6, 2013. Outline. Introduction to network programming Socket programming BSD Socket WinSock Java Socket Exercises. Introduction. Internet TCP/IP protocol stack Client-server model What do you need: client or server? Programming experience

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Network Programming

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  1. Network Programming By J. H. Wang Nov. 6, 2013

  2. Outline • Introduction to network programming • Socket programming • BSD Socket • WinSock • Java Socket • Exercises

  3. Introduction • Internet • TCP/IP protocol stack • Client-server model • What do you need: client or server? • Programming experience • C, C++, Java, … • Tools needed • C/C++/Java Compiler • Packet sniffers

  4. What’s a Socket • Source IP, port • Destination IP, port • Protocol • TCP • UDP • Connection method • Connection-oriented: SOCK_STREAM • Connectionless: SOCK_DGRAM

  5. Socket Programming • UNIX BSD socket (in C) • Windows socket (in Dev-C++) • Java socket API • Perl, Python, …

  6. Berkeley Socket • General functions • open(), connect(), close(), send(), recv(), … • Functions for servers • bind(), listen(), accept() • select(), FD_SET, FD_CLR, FD_ISSET, …

  7. An Example BSD Socket Program – a simple client (1/2) • #include <sys/socket.h>#include <netinet/in.h> // for struct sockaddr_in#include <netdb.h> // for gethostbyname()struct sockaddr_in dest;struct in_addr in;struct hostent *phe;char host[1000];int fd, port = 80;dest.sin_family=AF_INET;dest.sin_port = htons(port);if (phe = gethostbyname(host)) bcopy(phe->h_addr, (char *)&dest.sin_addr, phe->h_length);

  8. An Example BSD Socket Program – a simple client (2/2) • fd = socket(PF_INET, SOCK_STREAM, 0);in.s_addr = dest.sin_addr.s_addr;connect(fd, (struct sockaddr *)&dest, sizeof(dest));send(fd, msg, strlen(msg), 0);…recv(fd, buf, sizeof(buf), 0);…close(fd);

  9. Windows Socket • WSAStartup(), WSACleanup() • socket(), connect(), close() • send(), recv() • …

  10. An Example WinSock Client (1/2) • #include <winsock.h>SOCKET fd;SOCKADDR_IN dest;WSADATA WSAdata;struct hostent FAR *ent;int port = 80;WSAStartup(0x1010, &WSAdata);fd = socket(PF_INET, SOCK_STREAM, 0);dest.sin_family = PF_INET;dest.sin_port = htons(port);ent = gethostbyname(hostname);

  11. An Example WinSock Client (2/2) • connect(fd, (LPSOCKADDR)&dest, sizeof(SOCKADDR));send(fd, msg, strlen(msg), 0);…recv(fd, buf, sizeof(buf), 0);…close(fd);WSACleanup();

  12. Java Socket • java.net.Socket • new • getInputStream • getOutputStream • close • java.net.ServerSocket • new • accept • close

  13. An Example Java Socket Client (1/2) • import java.net.Socket;import java.net.InetSocketAddress;import java.io.BufferedOutputStream;import java.io.BufferedInputStream;public class SockClient { private String address = hostname; private int port = 80; public SockClient() { Socket client = new Socket(); InetSocketAddress isa = new InetSocketAddress(this.address, this.port);

  14. An Example Java Socket Client (2/2) • try { client.connect(isa, 10000); BufferedOutputStream out = new BufferedOutputStream(client.getOutputStream()); BufferedInputStream out = new BufferedInputStream(client.getInputStream());out.write(…);in.read(...);in.close();out.close();client.close();} catch () {}

  15. Response Parsing • Protocol dependent • browser • HTTP over TCP: connection-oriented • Byte ordering • Buffer management

  16. Some Protocols in Web Programming • HTTP • HTML • JSON (JavaScript Object Notation) • XML

  17. HTTP • HyperText Transfer Protocol • The protocol standard for the World Wide Web • Defined by IETF, W3C • RFC 2616, HTTP 1.1 • Overview • Web browser (the HTTP client) submits an HTTP request to the HTTP server, which provides resources (such as HTML files) and returns a response

  18. HTTP Request Message • Request line: • GET /images/logo.png HTTP/1.1 • Headers • Accept-Language: en • Empty line • (Each line must end with <CR><LF>) • Optional message body

  19. Request Methods • 9 methods indicating the action to be performed on the identified resource • GET • POST • PUT • DELETE • HEAD, TRACE, OPTIONS, CONNECT, PATCH

  20. Some HTTP Header Fields • Requests • Accept-Charset • Connection • Content-Type • Content-Length • Date • From • Host • Responses • Connection • Content-Type • Content-Length • Date

  21. Response Message • Status line • Status codes • 404 • Reason phrase • Not found • Types of status codes • 1xx informational • 2xx success • 3xx redirection • 4xx client error • 5xx server error

  22. Example HTTP Session • Client request • GET /index.html HTTP/1.1<CR><LF> • Host: www.example.com<CR><LF> • <CR><LF> • Server response • HTTP/1.1 200 OK • Date: Mon, 23 May 2005 22:38:34 GMT • Server: Apache/1.3.3.7 (Unix) (Red-Hat/Linux) • Last-Modified: Wed, 08 Jan 2003 23:11:55 GMT • Etag: “3f80f-1b6-3e1cb03b” • Accept-Ranges: bytes • Content-Length: 438 • Connection: close • Content-Type: text/html; charset=UTF-8

  23. HTML • HyperText Markup Language: the language for Web pages • HTML 4.01 (W3C recommendation, 1999) • HTML 5 (W3C working draft, May 2011) • Elements • Tags: <xxx> … </xxx> • Attributes • Ex: headings, paragraphs, tables, forms, comments, …

  24. An Example HTML File • <html> <head> <title>Hello HTML</title> </head> <body> <p>Hello World!</p> </body> </html>

  25. JSON • JavaScript Object Notation (JSON): a lightweight data-interchange format (http://www.json.org/ ) • Easy for humans to read and write • Easy for machines to parse and generate • Based on a subset of JavaScript Programming Language, but it’s completely language independent • JSON is built on two structures • Name/value pairs: objects • Ordered list of values: arrays • More details in RFC 4627

  26. JSON Examples • { "Image": { "Width": 800, "Height": 600, "Title": "View from 15th Floor", "Thumbnail": {"Url":"http://www.example.com/image/481989943", "Height": 125, "Width": "100" }, "IDs": [116, 943, 234, 38793] } }

  27. JSON Examples • [ { "precision": "zip", "Latitude": 37.7668, "Longitude": -122.3959, "Address": "", "City": "SAN FRANCISCO", "State": "CA", "Zip": "94107", "Country": "US" }, { "precision": "zip", "Latitude": 37.371991, "Longitude": -122.026020, "Address": "", "City": "SUNNYVALE", "State": "CA", "Zip": "94085", "Country": "US" } ]

  28. XML • eXtensible Markup Language: a set of rules for encoding documents in machine-readable form • XML 1.0 (W3C Recommendation) • An application profile of SGML (ISO 8879)

  29. An Example XML File • <?xml version="1.0"?><note>    <to>Tove</to>    <from>Jani</from>    <heading>Reminder</heading>    <body>Don't forget me this weekend!</body></note>

  30. Programming Exercises • Packet sending/receiving • {Source, destination} (IP, port number) • Protocol • A simple HTTP client • To get a Web page at any URL • To display the page content

  31. Thanks for Your Attention!

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