EE 607 Spring 2008 Project 1

Due date: See EE 607 Spring 2008 Project Web Page

For this assignment you will write (actually modify) C code for a client and server.

The server will serve files. It should be located in one of your UNIX accounts and in its own directory. In the directory, you should also have the following text files (these can be downloaded by clicking them):

The client will get a file from the server and print it out on the terminal. If the file is not found then the client prints out a corresponding message. The following is an example of using a client, assuming its executable has been renamed "getfile". Shown in red are what was typed in, and shown in green are the responses from the computer.

getfile file1.txt

Aloha!

You have reached file 1.
This means that your client and server works at least partially.
Congratulations!!

Adios

getfile whoa

File "whoa" not found

Instruction

Step 1. Read Beej's Guide to Network Programming
Step 2. Modify the Simple Stream Server and Simple Stream Client into your server and client. To test, you can use ephemeral ports between 2000 and 5000.

Step 3. Email me your client on the due date, before midnight. You should code should compile and run on spectra. Turn in

source code
makefile
README file (text), that describes how to operate your client. Include your

Name
EE 607, Spring 2008, Project number (e.g., Project 1)
Date
Instructions to compile. If you have a makefile, these instructions could simply be, "enter makefile"
Instructions to run the program

by tar'ing and gzipping it. tar is a UNIX command to combine all files in a UNIX directory into a single file. The command to tar a directory is

tar cvf Name.tar Dir

where "Dir" is the directory to be tarred, and "Name.tar" is the name of the new file. For all your assignments, label the directory "YourNameProjectX", where YourName is your family name then given name, and Project X is the current project, e.g., SmithTomProject1". To untar a file, enter

tar xvf Name.tar

Now, gzip is the compression algorithm for UNIX. To compress a file, enter

gzip file

which will produce a file "file.gz". To uncompress the file, enter

gunzip file.gz

Step 4. After you turn your client in, I will give you instructions to run your server on spectra at a particular port number. Run it for a couple of days in background (e.g., type "./a.out &"). Afterwards, you can kill the job by first finding its id using ps, and then killing it using "kill". For more information, see the man pages of your machine.

Note: To launch an executable program such as "a.out", type "./a.out". The prefix "./" is what is accepted by UNIX today. I believe it is a security upgrade.

Hints:

Download the client.c and server.c files from Beej's Guide. Make sure you can compile this on specta. I was able to compile using (note that this was suggested in Beej's Guide under Notes for Solaris/SunOS, but there the example was for "cc" rather than "gcc"):

gcc client.c -lnsl -lsocket -lresolv

Examine client.c and server.c. Beej's Guide explains what's there but basically there's two parts. First, a connection is set up using "connect" and "accept" . Second data is transferred using "recv" and "send". Note that both "recv" and "send" can be used at client and server to transfer strings of bytes. In the examples of client.c and server.c, file descripters "sockfd" and "new_fd" are used.
For client.c, the host name of the server is given as an argument, argv[1].
Many of the modifications will be using functions that do character string operations and opening, closing, reading, and writing to files. If you're rusty with C then check these sites: C Programming Tutorial, Tutorial From Physics Dept Drexel U.. The last site is pretty good since it has examples. This site has a bunch of links about C. For practice, write a short program that will have as arguments two file names and it copies the first file to the second file. Before copying, your program should check if the first file is there and the second file does not already exists, since you want to avoid overwriting an existing file. A string function that is useful is "strlen" which returns the length of a string. For IO, some of the key operations are fopen, fclose, fscanf, fread, getchar, and printf.
Note that to run an executable, say "a.out", on spectra, the command line is "./a.out"
Write your code in stages, starting from the original client.c and server.c code. Have the client send a file name to the server. Then have the server return the file name it received back to the client. Then have the server open a file and send it to the client.