本次作業要時做一個能相容目前瀏覽器的 simple web server，server program 要包含兩個參數，分別是

• port number
• document root directory of the server

port number 用於接收進來的連線，document root directory 用來存放 web page 和相關資源

Example to launch the web server:

$ ./webserver 8888 "/path/to/your/webserver/docroot"

實作上 web server 必須提供以下 feature

• [basic] GET a static object
• [basic] GET a directory
• [optional] Execute CGI programs

GET a static object

可能的 static object type：

• text files
• html files
• scripts
• style sheet files
• images
• audio files
• video files

可能情況：

• If a requested object can be found, your server has to return “200 OK” status as well as the proper headers and content for the browser to render the document correctly.
• If a requested object does not exist, your server has to return a “403 FORBIDDEN” status and provide error messages.
• If a requested object is inaccessible, your server has to return a “404 NOT FOUND” status and provide error messages.
• If a requested object is an accessible directory, please follow the descriptions in the next section.
• If a requested URL contains a question mark (?), you can simply ignore the question mark and all texts after the mark.
• Note that we INTENTIONALLY use 403 error code for missing objects and 404 error codes for inaccessible objects.

GET a directory

• If a requested object is a directory, your program have to check whether the requested directory has a slash (/) at the end of the URL.
• If the URL does not have a slash suffix, you have to respond a “301 MOVE PERMANENTLY” status and a new location with a slash appended to the original requested URL.
• If a slash is already given in the URL, your server has to search for a default index file, e.g., index.html, in the directory.
• If there is a readable index.html file, you can simply send the content of index.html back to the browser.
• If there is a readable index.html file, but it is not readable, you can simply send “403 FORBIDDEN” status to the browser.
• If there is not a readable index.html file, but the directory is readable, you have to list the files and directories found in the requested directory. The list can be in either a plain-text document or a html document.
• It would be a plus if your response is a html document with hyperlinks point to the location of files and directories in the requested directory.
• If there is not a readable index.html file, and the directory is not readable, you have to send “404 NOT FOUND” status to the browser.

Execute CGI programs

• Implement CGI execution using GET requests: Environment variable - REQUEST_METHOD=GET
• If a question mark (?) is used in the URL, add the content after (?) into a environment variable QUERY_STRING.
• Execute the sample CGI provided by this homework. You will have to setup a pipe to forward outputs from a CGI script to the browser.
• Implement CGI execution using POST requests: Environment variable - REQUEST_METHOD=POST. You will also have to setup a pipe to forward inputs from the browser to the CGI script.