CSCI 6356 Fall 2000
Xiannong Meng Programming Assignment Three
Assigned: Thursday November 2, 2000 Due: Thursday November 16, 2000

In this assignment you will use pthread to write a program that can retrieve web pages automatically. The main thread accepts a request from the user. The request should include the URL and an optional file name in the following form:
url filename
For example www.cs.panam.edu index.html meaning the user wants to visit the site www.cs.panam.edu and requests a specific file index.html. Once receiving the request from the user, the main thread forks a work thread and the thread will be responsible to retrieve the page specified by the user. While the thread is working on the user requested page(s), the main thread should return to handle more user requests. At any moment there could be multiple threads working on multiple requests from the user. The main thread also needs to keep a counter as how many requests have been serviced.

The HTTP Protocol
To retrieve a web page, the client and the web server need to communicate with each other using a fixed protocol. This protocol is called the Hyper Text Transfer Protocol or HTTP for short. The protocol itself is evolving. But the following is a sequence of basic steps how the two (the server and the client) communicate.

1. The client requests a connection to the server at a known IP address (or hostname) with a known port number.
2. The client then sends the requests to the server. The request has to be in certain format.
3. The server takes the requests and returns the results to the client. The result can be the pages that the client requested or can be an error message if something is wrong in the query.

The following is an example:

client:  Open connection at www.cs.panam.edu
client:  Send request: GET / HTTP1.1\n\n
server:  Send back the page http://www.cs.panam.edu/

For details of how this works see the program example at
<http://www.cs.panam.edu/~meng/Course/CS6356/Handout/Html/>

Pthread
The Pthread has been discussed in the class. Click
<http://www.cs.panam.edu/~meng/Course/CS6356/Handout/Pthread/> for more examples.

Hand in: Please email me by the due date the location of your program in our lab computers. I'll go there and check it on-line. For those who work outside our lab, please ftp your program to the lab so that I can check them on-line.

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