Enscript Output

COMS W3157 Advanced Programming, Lab #7 (150 points total)
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Please read this assignment carefully and follow the instructions
EXACTLY.

Submission:

Please refer to the lab retrieval and submission instruction. The
requirements regarding README.txt and Makefiles remain the same as the
previous labs unless specified otherwise.

For this lab, do not make part1 and part2 directories. Just put your
part2 files directly in lab7 directory. There are no files to submit
for part1.

Checking memory errors with valgrind

Do not include valgrind output in README.txt. You should keep using
valgrind to check your program for memory error (and the TAs will do the
same when grading), but you don’t have to include the output in
README.txt anymore.

Part 1: Build a web page on your account
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Follow this instruction from CRF to setup a web page on your CLAC account:

http://www.cs.columbia.edu/~crf/newweb/index.html

Your page at “http://clac.cs.columbia.edu/~YOUR_UNI/cs3157/tng/” will show
the same web page that http://clac.cs.columbia.edu/~jae/cs3157/tng/ shows.
(You are allowed to tweak it though, as described later.)

You can copy the files that make up the web page (index.html, crew.jpg and
ship.jpg) from Jae’s account. Your job is to construct an appropriate
directory structure under ~/html to place the 3 files in order for the URL
to work. You may also need to modify the permissions on the directories and
files. Directories under ~/html should have 711 and files should have 644.

There is nothing to submit for this part, other than your statement in your
README.txt that you have setup your web page. The TAs will test this part
by pointing browser to “http://clac.cs.columbia.edu/~YOUR_UNI/cs3157/tng/”.

If you feel creative, or don’t care much about Star Trek, you are welcome to
replace the content of the web page. But please don’t change the file
names, directory hierarchy, and the web page structure. That is, there must
be index.html, crew.jpg, ship.jpg (with the same directory hierarchy as
mine), and index.html must have two tags, images/ship.jpg and
images/crew.jpg. Those images should be immediately visible without user
interaction, JavaScript, or CSS. Apart from those guidelines, feel free to
get creative! Post a link to the listserv if you make something cool or
funny.

miezai
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Part 2: Write a web server
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(a) Serving static contents
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In this part, you are writing a web server, named http-server, that can
serve static HTML and image files. The http-server takes the following
parameters:

./http-server

server_port is the port that you’re listening for HTTP requests and
web_root is the top level directory for your HTML files. The last two
parameters are for part 2(b). For example:

./http-server 8888 ~/html localhost 9999

should serve the Star Trek page to the following request:

http://the.machine.your.server.is.running.on:8888/cs3157/tng/index.html

Writing a web server is not a trivial task. Although you’re all
super-coders at this point, since you only have a few days, we need to
cut some corners. Here is the list of what is expected and what is
not expected from your web server:

– It will only support the GET method. If a browser sends other
methods (POST, HEAD, PUT, for example), the server responds with the
status code 501. Here is a possible response:

HTTP/1.0 501 Not Implemented

501 Not Implemented

Note that the server adds a little HTML body for the status code and
the message. Without this, the browser will display a blank page.
This should be done for all status codes except 200.

– Our server will be strictly HTTP 1.0 server. That is, all responses
will say “HTTP/1.0” and the server will close the socket connection
with the client browser after each response.

The server will accept GET requests that are either HTTP/1.0 or
HTTP/1.1 (most browsers these days sends HTTP/1.1 requests). But it
will always respond with HTTP/1.0. The server should reject any
other protocol and/or version, responding with 501 status code.

– The server should also check that the request URI (the part that
comes after GET) starts with “/”. If not, it should respond with
“400 Bad Request”.

– In addition, the server should make sure that the request URI does not
contain “/../” and it does not end with “/..” because allowing “..” in the
request URI is a big security risk–the client will be able to fetch a
file outside the web root.

miezai
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– You may find the following sequence of code handy for parsing the
request line:

char *token_separators = “\t \r\n”; // tab, space, new line
char *method = strtok(requestLine, token_separators);
char *requestURI = strtok(NULL, token_separators);
char *httpVersion = strtok(NULL, token_separators);

See man strtok for explanation.

– The server must log each request to stdout like this:

128.59.22.109 “GET /cs3157/tng/images/ship.jpg HTTP/1.1” 200 OK

It should show the client IP address, the entire request line, and the
status code and reason phrase that it just sent to the browser.

– The server should be robust against client failure. For example, if the
client browser crashes in the middle of sending a request, the server
should simply close the socket connection and move on to the next client
request.

This means that, in your code, you can’t just die() on every
failure. You need to think about which errors are recoverable (or
ignorable) and which are not.

You can simulate the client failure by using netcat: just Ctrl-C in
the middle of typing a request.

– If the request URI ends with ’/’, the server should treat it as if
there were “index.html” appended to it. For example, given

http://localhost:8888/cs3157/tng/

the server will act as if it had been given

http://localhost:8888/cs3157/tng/index.html

– If the request URI is a directory, but doesn’t have ’/’ at the end —
“http://localhost:8888/cs3157/tng”, for example — you should append
“/index.html” to it.

Use stat() function to determine if a path is a directory or a file.

– The server sends “404 Not Found” if it’s unable to open the
requested file.

– For reading the file, you can use fread() or read(). You should
read the file in chunks and send it to the client as you read each
chunk. The chunk size should be 4096 bytes (that’s 4K, the
optimal buffer size for disk I/O for many types of OS/hardware).

Do not read the file one character at a time using fgetc() or
getc(). Do not read the file one line at a time using fgets()–this
may not work for image files.

miezai
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(b) Serving dynamic contents
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In this part, you’ll add the mdb-lookup functionality to your web
server. Your web server will work in conjunction with
mdb-lookup-server from lab6, part1.

You can test it out using my versions, available in
/home/jae/cs3157-pub/bin:

1) Start mdb-lookup-server with the class database file:

./mdb-lookup-server mdb-cs3157 9999

2) Open up another terminal window into the same machine and run
http-server, which will connect to the mdb-lookup-server you started
earlier:

./http-server 8888 ~/html localhost 9999

3) Point your browser to:

http://the.host.name:8888/mdb-lookup

4) If you type “hello” into the text box and submit, you will see a
few messages containing hello nicely formatted in a HTML table.
If you look at the location bar of the browser, you’ll see that
it went to this URL:

http://the.host.name:8888/mdb-lookup?key=hello

Here are the requirements and hints for implementing this
functionality in your server:

– You must make a TCP connection to the mdb-lookup-server when the web
server starts up, and keep using the SAME socket connection. There
is only a single persistent connection to the mdb-lookup-server
during the execution of the web server.

Using that connection, you can send the search string and read back
the result rows. You can detect the end of result by reading a
blank line.

Also, make sure to append “\n” to the search string before you send
it to mdb-lookup-server. (Think about why.)

– When the request URI is simply “/mdb-lookup”, you send the submit
form. You can hard-code the form in your program like this:

const char *form =
“

mdb-lookup

\n”
“

\n”;

(Note that C language automatically concatenates adjacent string
literals.)

– If the request URI starts with “/mdb-lookup?key=”, you send the
lookup result table in addition to the form.

Since you don’t know how big the lookup result will be, it would be
easiest to send the resulting HTML table piece-by-piece as you read
each line from the socket connection to the mdb-lookup-server. It
is easy to format a HTML table on the fly (see the HTML source of
the lookup result from your browser to learn how to construct an
HTML table).

– Make sure the logging you implemented in part 2(a) still works for
the mdb-lookup requests.

—

Good luck!

501 Not Implemented

mdb-lookup

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