CS 336/621

PROJECT #1                                 Due: 7:30pm, Tuesday 03/10/09


     The purpose of this project is to introduce students to programming
of network applications in C/C++ using the Berkeley sockets API. 


			   PROBLEM STATEMENT
	
     This project asks the student to write an application program named 
'showpath.cpp' which uses the sockets API to implement a much simplified 
version of the standard 'traceroute' algorithm, based on sending out UDP 
datagrams to a specified destination and obtaing the intermediate router 
addresses as ancillary data provided by the 'recvmsg()' socket function.


			     REQUIREMENTS

     The user of your 'showpath' utility should be allowed to supply the
hostname (or IP-address) of a target station as a command-line argument,
like this:

			$ ./showpath sfsu.edu    


At a minimum, your 'showpath' utility should display IP-addresses of the
routers encountered along a network path toward your user's destination,
as for example:

 	tracing a network path to sfsu.edu (130.212.10.239) 

		ttl= 1  hop: 138.202.171.254 
 		ttl= 2  hop: 138.202.128.202 
 		ttl= 3  hop: 137.164.38.80 
 		ttl= 4  hop: 137.164.24.2 
 		ttl= 5  hop: 137.164.22.33 
 		ttl= 6  hop: 137.164.40.82 
 		ttl= 7  hop: 130.212.253.68 
 		ttl= 8  hop: 130.212.199.252 
 		ttl= 9  hop: 130.212.10.239 


You will need to decide how to handle any cases when a specifed station
cannot be reached.  


			     EXTRA CREDIT

     You have several opportunities to add your own enhancements to the 
basic functionality required for 'showpath.cpp' -- if you want to learn 
more about network programming and earn extra credit.  (You can examine 
the official Linux 'traceroute' tool for some ideas along this line, or
Linux's alternative 'tracepath' utility.)  For enhancements you add, be 
sure to include a brief statement in your source-file's 'comments' that 
explains how a particular enhancement makes your utility more useful.  


			    WHAT TO SUBMIT

     Your project-submission has two required parts: 

	(1) a printout of your source-file (i.e., 'showpath.cpp');

	(2) electronic copies of all of your program-files; 

Use our 'ljpages' utility-program (under 'System Software' on our cs336
website) to produce your printout on a laserprinter in our classroom or
in one of the Harney Fifth-Floor CS Labs -- Be sure your printout shows
YOUR NAME as the project's programmer -- and turn in your 'printout' to 
your instructor's mailbox (Mathematics Office: Harney-222) or in class.  
Submit project files ('showpath.cpp' and 'showpath') electronically, by
copying them into your cs336 '/submit' directory, where your instructor 
can access them for doing testing and grading:

	   $ cp showpath* /home/submit/cs336/<your_directory>/.
________________________________________________________________________
Allan B. Cruse          University of San Francisco          Spring 2009