This project starts as a course assignment, but I also aimed to achieve and learn more during the process.

The source code is at src/main.c.

• The program runs as a static file server, serving all files under the directory ./static. To let the server runs properly, index.html and 404.html is required.
• Url / is directed to /index.html.
• It determines the MIME type of a file by its extension, so that the browser can process them correctly
• When a resource is not found, it returns /static/404.html with status code 404.

• The browser caches the content via the Cache-Control header.
  • Motivation: browser doesn't need to load a resource that it has loaded twice
• The server send its content using deflate compression algorithm, which all browser nowadays support. (By using the zlib.h library)
  • Motivation: The transmission size is much smaller after compression, so the loading time will decrease, especially under not-so-well network condition.

The program can be built and run on the cse lab machine, or any Linux machine with glibc, gcc(>=9) and zlib. It is NOT Posix compatible, as it uses some linux only system calls, e.g. accept4(), pthread_yield()

# Build the binary
# Use the newest version of gcc available on the cse lab machine
echo "CC=gcc10 make" | bash
# Run the binary
# Port can be specified by the `SERVER_PORT` environment variable
echo "SERVER_PORT=8081 src/main" | bash

The program is implemented in c.

I first copy the source code from Lab3, then made the following major change:

• Feature: the main logic of HTTP is implemented in void* request_func(void*)
• Feature: the compressing part is implemented in int pipe_fd(int src, int dest)
• Feature: the MIME determination is implemented in int ext_to_mime(char *buff, size_t buff_len)
  • More types can be easily supported by editing that function
• Socket: the connection socket is non-blocking, so that thread can gracefully exit after timeout
• Error handling: non-fatal error will not cause the server to terminate, only the corresponding TCP connection will terminate
• Threading: Use a semaphore to count running thread. Server can run forever without "running out of threads"
• Threading: A thread terminates itself if the client is unresponsive for 30 seconds.
• Security: HTTP Requests like GET /../../../../../etc/passwd HTTP/1.1 will be rejected with 404.

• The url in the HTTP request does not accept the %XX hex format. E.g. %2E will not be converted to the space character.

Huang Meng ([email protected])

May 16, 2021