CSCI-4220 Network Programming

Project 2 - Proxy Web Server
Due Date: Feb 9th

Submission Instructions

You have been hired by Fox & Scully to develop a proxy web server that will track all the web sites visited by FBI personnel. Fox suspects that various factions within the FBI are using the WWW to communicate with aliens, your program will help by providing a log of all WWW accesses including the originator and requested URL. Your server should attempt to find out the identity of the user submitting each http request by using a authentication lookup as described in RFC 931. Some machines within the FBI don't run RFC 931 (a.k.a authd) servers, so your proxy server must be able to handle this condition (your server shouldn't die if it cannot contact an authd server).

Your server needs to handle only GET requests, you can ignore any other request methods. Your server should forward all HTTP headers included in a request to the target web server, and should send the complete reply back to the client (headers and contents).

Server Output

Your server should print (to stdout) out the port number it is running on as soon as it starts. Using a fixed port number may make it difficult for us to grade (and for you to debug), so we suggest you allow the operating system to assign you any available TCP port. The initial line printed by your program should include the port number and nothing else (not "Port = 3838\n", just "3838\n"). Your program will be run by an automated system that expects this output.

To keep track of all requests, your server should print one line (to standard output) for each request serviced. The line should contain the username of the client (as returned by the RFC 931 lookup, or "unknown" if a RFC 931 server could not be contacted or any other failure occurred during the RFC 931 lookup), the host name of the client, and the original request sent by the client (not any of headers that accompanied the request). For example, the following lines would be printed if the user "skinner" on the machine xfile.fbi.gov was surfing the web:
 

skinner@xfile.fbi.gov: GET http://www.yahoo.com/headlines/news/ HTTP/1.0
skinner@xfile.fbi.gov: GET http://www.thewordistruth.org/ HTTP/1.0
skinner@xfile.fbi.gov: GET http://www.cs.rpi.edu/~hollingd/netprog/ HTTP/1.0

Deliverables

You should submit all the source code necessary to build your server and a makefile. Submission instructions are here. You must also include a brief writeup in a file named README that includes the following:

• A list of files and a 1-line description of the contents of each file.
• References to any borrowed code (the source code must also include this information).
• A description of any known problems. If you think you know how to solve the problem(s) and simply didn't have time to do so - let us know how!
• Anything else you think might be useful to us, such as what you learned, what you had trouble with, if the project was too hard or too easy, etc.

Computer Accounts

Make sure your code will build and run on the CS BSD machines. If you want to get fancy and write a concurrent server, you must not develop the code on an RCS machine (use the CS machines).

Tips, Hints, Suggestions

• ReadRFC 931.
• Read RFC 1945 HTTP 1.0.
• An iterative server is fine for this assignment.
• Develop and debug code for doing RFC 931 lookups independently of the proxy web server, when both are working it should be simple to put them together (and simplifies debugging).
• Start out using telnet as a client for testing, once things seem to work you can use Netscape as a client. Some things might not work, but you should be able to browse much of the WWW normally (anything that requires the client to submit requests other than a GET won't work). To tell Netscape (4.0) where your proxy server is:
• Click on "Preferences" in the Edit menu.
• Click on "Advanced".
• Click on "Proxies".
• Select Manual Proxy configuration.
• Click on the "View" button.
• Fill in the host name and port number of the HTTP proxy with the machine and port that is running your server.
• Click on OK
• Click on OK

• I will be updating a Project 2 FAQ with common questions and answers.
• A sample server (binary only) is available on the CS machines: ~hollingd/netprog/webproxy.
• Read section 5.13 in the book - it describes some of the conditions that can cause a SIGPIPE (something you need to deal with).
• Much (possibly all) of the testing of your program during grading will be automated. Make sure the first line contains only a port number, and that the logging is as described above (one line per request).