1 / 22

Common Gateway Interface (CGI)

Common Gateway Interface (CGI). Joe Komar. Common Gateway Interface (CGI). HTTP typically requests HTML pages Link (URL) can identify a non-HTML page WWW server invokes the resource named in the URL (a program, batch file, etc.) and lets it do its thing

Télécharger la présentation

Common Gateway Interface (CGI)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.


Presentation Transcript

  1. Common Gateway Interface (CGI) Joe Komar Komar Associates

  2. Common Gateway Interface (CGI) • HTTP typically requests HTML pages • Link (URL) can identify a non-HTML page • WWW server invokes the resource named in the URL (a program, batch file, etc.) and lets it do its thing • Results of the CGI program are returned to the server in the form of HTML • Server then passes the HTML to the client Komar Associates

  3. HyperText Transfer Protocol (HTTP) • Provides “stateless” connection: • Client establishes connection • Client issues a request • Sever processes the request and returns a response • Server closes the connection • Web’s Remote Procedure Call (RPC) on top of TCP/IP Komar Associates

  4. HTTP Request • Request Line -- method (GET), relative path to resource (/temp/index.html), protocol version (HTTP/1.0) • Request header fields -- additional parameters in the format name, colon (:), value • Entity body -- sometimes used to pass bulk information to the server Komar Associates

  5. HTTP Request Example GET /path/file.html HTTP/1.0 (header line) Accept: text/html (request header fields) Accept: audio/x “ User-agent: MacWeb “ Komar Associates

  6. HTTP Response • Response header line -- HTTP version, status of the response, explanation of status • Response header fields -- server attributes and document returned metadata • Entity body -- typically an HTML document Komar Associates

  7. HTTP Response Example HTTP/1.0 200 OK (response header) Server: NCSA/1.3 (response header fields) Mime_Version: 1.0 “ Content_type: text/html “ Content_length: 2000 “ <HTML> (entity body) . “ </HTML> “ Komar Associates

  8. Common Gateway Interface • HTML FORMs allow user input • Input is packaged up in a known format and send as an HTTP request (POST or GET) and sent on through a CGI protocol • The program or resource named is given the data and left to do with it what it will • Results are returned in the form of an HTML document that the server passes on to the client • Three-tier client/server model Komar Associates

  9. Using FORMs and CGI • FORM’s submit button is pushed • Browser collects data and forms one long string of name/value pairs separated by an ampersand (&) with plus signs (+) for spaces • Browser forms a standard HTTP request with the long string as the “entity body” • Server receives request via a socket and starts a CGI interaction Komar Associates

  10. Using FORMs and CGI continued • Server sets up “environment variables” • shared “bulletin board” with cgi program • server_name, request_method, path_info, script_name, content_type, content_length, etc. • Server starts the CGI program • CGI program reads environment variables • CGI program receives message body (long string) via standard input and parses Komar Associates

  11. Using FORMs and CGI continued • CGI program does its thing and formats results in HTML • CGI program returns results via standard output • Server returns the results to the Browser • ALL DONE !! • Since the connection is “stateless” hidden fields are used in sequences of forms Komar Associates

  12. Example FORM <HTML> <BODY> <H1>Sending POST Data to a CGI Program</H1> <FORM ACTION= "" METHOD="POST"> Enter some data: <INPUT TYPE="TEXT" NAME="TextField1"><BR> Enter some more: <INPUT TYPE="TEXT" NAME="TextField2"><BR> <INPUT TYPE="SUBMIT" VALUE="Send It"> </FORM> </BODY> </HTML> Link Komar Associates

  13. Count CGI Version (Client Applet) import java.awt.*; import java.applet.*; import java.io.*; import java.net.*; import java.util.*; public class CountCGIClientApplet extends Applet { Komar Associates

  14. Count CGI Version (Client Applet) try { String sum = "0"; showStatus("Incrementing"); int count = new Integer(textField1.getText()).intValue(); long startTime = System.currentTimeMillis(); for (int i = 0 ; i < count ; i++ ) { sum = increment(sum); } long stopTime = System.currentTimeMillis(); list1.addItem("Avg Ping = " + ((stopTime - startTime) / (float)count) + " msecs"); showStatus("Sum = " + sum); } catch(Exception e) { showStatus("System Exception" + e); } Komar Associates

  15. Count CGI Version (Client Applet) public String increment(String currentSum) { String script = "/cgi-bin/Count.bat"; Socket socket = null; String rdata = ""; String line = ""; String lastLine = ""; Komar Associates

  16. Count CGI Version (Client Applet) try { socket = new Socket(getCodeBase().getHost(), 80); PrintWriter ostream = new PrintWriter(socket.getOutputStream()); BufferedReader istream = new BufferedReader( new InputStreamReader(socket.getInputStream())); ostream.print("POST " + script + " HTTP/1.0\r\n" + "Content-type: text/plain\r\n" + "Content-length: " + ("increment " + currentSum).length() + "\r\n\r\n"); ostream.print("increment " + currentSum + "\r\n"); ostream.flush(); Komar Associates

  17. Count CGI Version (Client Applet) try { while ((line = istream.readLine()) != null) { list1.addItem(line); lastLine = line; } } catch ( SocketException e ) { istream.close(); ostream.close(); } Komar Associates

  18. Count CGI Version (Server) import java.io.*; import java.util.*; class CountCGIServer { public static void main(String[] args) { int count; String line; try { // create streams PrintWriter ostream = new PrintWriter(System.out); BufferedReader istream = new BufferedReader( new InputStreamReader(System.in)); line = istream.readLine(); StringTokenizer tokens = new StringTokenizer(line); String myOperation = tokens.nextToken(); Komar Associates

  19. Count CGI Version (Server) if(myOperation.equals("increment")) { String countString = tokens.nextToken(); count = Integer.parseInt(countString); count++; ostream.println( Integer.toString(count) ); ostream.flush(); } istream.close(); ostream.close(); } catch (Exception e) { System.out.println("Error " + e); } } } Komar Associates

  20. Count CGI Html and Batch Files <html> <body> <h1>Count CGI Client Applet</h1> <hr> <center> <applet code=CountCGIClientApplet.class width=500 height=500> </applet> </center> </body> </html> d:\jdk1.1.7a\bin\java CountCGIServer Do it! Komar Associates

  21. Java and CGI Helpful Link Marty Hall’s CGI page Komar Associates

  22. CGI Assignment • Stay tuned…. Komar Associates

More Related