Assignment 6: Web Server

Due by: Friday, March 28, 2025 at 11:59 p.m.

In this assignment, you'll create a simple web server.

As with all the assignments and projects in this course, it's recommended that you do the stages in the order given. Try to get the MIN unit tests passing before moving on to the FULL ones. Likewise, try to get the MIN integration tests passing before moving on to the FULL ones.

First, download the archive given below and unzip it into an appropriate directory.

String Issues

Although this assignment is about networking, HTTP requires a lot of string manipulation. Assembling headers will require careful allocation and concatenation of strings. Here's an example of careful concatenation of "hello" and "world". 

// Allocate enough space for "hello"
char *str = malloc (strlen("hello") + 1);
// Copy "hello" over
strncpy (str, "hello", 6);
// Second string can be read-only data because it's only being copied
char *second = " world";
// Resize the "hello" string to make space (don't forget the null byte)
str = realloc (str, strlen (str) + strlen (second) + 1);
// Append 6 bytes of the second string to the newly sized buffer
strncat (str, second, 6);

Stage 1: Set up a Minimal HTTP Server

Please consult the extended example at the end of Chapter 4 in the textbook. It documents a lot of the steps for setting up a web server.

For the first stage, you will set up an HTTP server, receive an incoming request, and then respond with one of two messages: a hard-coded 200 OK and HTML file, or a hard-coded 404 Not Found message.

Make the following edits in utils.c. Use the TODO: comments in the file to guide the specific steps you need.

  1. Complete the server setup procedure in setup_server(), which should establish and return a server socket file descriptor.
  2. Complete get_connection(), which should use accept() to get an incoming request and return the IPv4 address of the client.
  3. Finish the implementation of build_response(), which builds a basic HTTP response. The first part is done to create the initial headers. Complete the headers to be a valid HTTP response. Don't forget the extra "\r\n" for the blank line at the end of the headers. Return the full header.

Complete the implementation of serve_web() in server.c to use the functions you just built. Again, use the TODO: comments to guide your steps.

Stage 2: HTTP/1.1 and Files

Enhance the following aspects of your implementation of utils.c and server.c:

  1. Allow support for HTTP/1.1 requests. All such responses must have an additional "Connection: close\r\n" in their headers. Also, you need to make sure your responses are writing HTTP/1.1 instead of HTTP/1.0.
  2. Add support for arbitrary files. Instead of hard-coding the file contents, use the opened file descriptor in build_response() to read in the file, printing that HTML content to the screen. In server.c, use write() to send back both the headers and contents of the HTML file.
  3. Remove the hard-coded check in server.c to use /index.html for any other URI. Instead, rely on the call to build_response(), which returns NULL if the file wasn't found.
  4. Allow a URI of "/", which indicates that the user is looking for the file directory, which is stored in /index.html.

Turn In

First, run make clean to remove all of the executable and object files from your directory structure. Then, zip up the contents of your project directory in either a .zip or a .tar.xz file. Upload this archive to Brightspace. Your assignment must be submitted by Friday, March 28, 2025 at 11:59 p.m. Grace days are not available for assignments.

All work must be done within assigned teams, though you may discuss general concepts with your classmates. Please refer to the course policies if you have any questions about academic integrity. If you have trouble with the assignment, I am always available for assistance.

Under no circumstances should any member of one team look at the code written by another team. Tools will be used to detect code similarity automatically.

Code that does not compile will automatically score zero points.

Grading

Your grade will be determined by the following categories.

Category Description Weight
Compiling Code Free points! 15%
Unit Tests Your solution passes the three unit tests. 21%
Integration Tests Your solution passes the eight integration tests. 64%

Credits

This assignment is based on material from CS 361 by Michael S. Kirkpatrick. This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.