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Operating Systems
Homework Assignment #5
Due 15.1.2014, 23:59

Part 1
In this section you will write an HTTP server.
The HTTP server listens for connections, with worker threads constantly running in the background. Whenever a
client connects, its socket is enqueued to a shared queue, to be handled by one of the worker threads.
Write a program http_server.o. It will receive three arguments: number of threads, max requests, and port
number. Port number is an optional argument, use default HTTP port if not provided.
Implement a shared Queue data structure:







Implemented by a linked-list (singly-linked) with a global lock, and head and tail pointers.
The maximal size of the queue is determined by the 𝑚𝑎𝑥 𝑟𝑒𝑞𝑢𝑒𝑠𝑡𝑠 argument. On an enqueue operation
that exceeds this size, return an error code (-1) to the calling thread.
You may assume max 𝑟𝑒𝑞𝑢𝑒𝑠𝑡𝑠 ≥ 0, where an argument of 0 is valid and can be used for testing.
To enqueue or dequeue, grab the lock and perform the required operation.
o Grab and release the lock in appropriate places! Do not hold the lock for performing operations
where the lock isn’t needed (allocating a queue item before enqueue, etc.).
Use condition variables where appropriate.

In the main thread:



Create the required number of worker threads.
Create a socket and listen for incoming connections.
o When a connection is made, enqueue the new socket into the shared queue.
o If the queue is full, return Service Unavailable (HTTP 503) to the client and close the connection.

In each worker thread, repeatedly:







Dequeue a socket item from the queue.
Read the client’s HTTP request and parse it.
o Only GET/POST operations – return Not Implemented (HTTP 501) for any other operation.
o Do not parse any info except the request line. Ignore request headers, cookies, etc.
Return a minimal HTTP response to the client according to the request
o Find the requested file on your machine (treat it as a path).
o If it is not found, return Not Found (HTTP 404) response (including simple body).
o If it is a directory, create a simple HTTP body listing the directory’s contents.
o If it is a file, return an HTTP response with the file’s contents as the body.
Close the socket.

Pressing CTRL+C (SIGINT) should exit the server properly!
i.e., use a signal handler to stop any running threads, close sockets, etc., before terminating.
You can & should wait for threads to finish handling any current clients before terminating (i.e., empty the queue).
Your browser should work with your server (navigate to URL ℎ𝑡𝑡𝑝://𝑙𝑜𝑐𝑎𝑙ℎ𝑜𝑠𝑡: < 𝑝𝑜𝑟𝑡 >/< 𝑓𝑖𝑙𝑒 >).
Source Exif Data: 
File Type                       : PDF
File Type Extension             : pdf
MIME Type                       : application/pdf
PDF Version                     : 1.4
Linearized                      : No
Creator                         : 
Create Date                     : 2014:12:28 23:00:01+02:00
Author                          : 
Subject                         : 
Title                           : 
Modify Date                     : 2015:07:27 12:35:10Z
Producer                        : 3-Heights(TM) PDF Security Shell 4.5.24.1 (http://www.pdf-tools.com) / pdcat (www.pdf-tools.com)
Page Count                      : 1
Language                        : en-US
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