Using Sockets

Warning: You can use only the packages that were used in the lecture notes.

Don't use any fancy packages not covered in the course.

In this lab, we will write simple programs using sockets.

[10pts] Part 1: Netcat chats

Finish Activity 1 in Class on sockets. In particular, bring up two terminals. Have a necat chat between the two terminals. Try a TCP connection, and then a UDP connection. In this case,

the server is the localhost. So, you can use IP address 127.0.0.1.
For the port number, you can use 9000 or a different port number that you choose.

Deliverables:

Two screeenshots in your lab report: one for a TCP chat, and the other for a UDP chat. Throught the semester, if you add screenshots, please add them in the lab report (along with explanations).

[25pts] Part 2: UDP netcat server

Finish Activity in Class on sockets. In particular, create a UDP netcat program (server part) called serv_udp.py. Your program should work with the following command:

nc -u ip_addr 9000

Refer to the socket manual page.

You need to give an additional parameter when calling socket() to create a UDP socket.
You still need to bind the socket to the service specific port (in our case, it's 9000).
However, UDP doesn't need to have the 3-way handshake as in TCP. So, you don't need to call listen() or accept().
For UDP, sendto() and recvfrom() should be used.
Use select() appropriately.
Have the program quit when the user types in "quit". Be sure to use strip() function for the input string to get rid of white space.

A sample run:

~$ python3 serv_udp.py
From ('127.0.0.1', 34001) : b'hello\n'
How are you?
quit

~$ nc -u 127.0.0.1 9000
hello
How are you?
^C

Note

For incoming packets, specify where it came from using the following format:
```
From ('ip', port) : 
```

Deliverables:

serv_udp.py
A screenshot in your lab report that shows your code works correctly.

[25pts] Part 3: HTTP Client

Write a TCP client program httpc.py that will successfully communicate with (i.e. send data to and receive data from) a remote server on port 80 (http).

Note

You can use only the packages that were used in the lecture notes. Don't use any fancy packages if they are not covered in the course.
Your understanding of how the HTTP protocol works is the big part of lab work.

Your program must connect to the remote server and then send a "GET" request for the main index web page.
- Read this page to figure out what kind of data your program should send through a socket. In particular, read the "HTTP Flow" section carefully.
Warning
- Most webservers would reject your HTTP request if it does not contain a Host header.
- Use b"\r\n" (instead of b"\n") for each new line.
- You should give two new lines at the end of the request.
You may want to see how a web-browser sends a HTTP request (with the Host header) using Wireshark. (If you want to use Wireshark in your VM, see the settings page.)
After the GET request is sent, your program should read the response from the server and print it out to the screen.

Sample runs:

~$ python3 httpc.py info.cern.ch
HTTP/1.1 200 OK
Date: Mon, 07 Jun 2021 21:40:35 GMT
Server: Apache
Last-Modified: Wed, 05 Feb 2014 16:00:31 GMT
ETag: "286-4f1aadb3105c0"
Accept-Ranges: bytes
Content-Length: 646
Connection: close
Content-Type: text/html

<html><head></head><body><header>
<title>http://info.cern.ch</title>
</header>

<h1>http://info.cern.ch - home of the first website</h1>
<p>From here you can:</p>
<ul>
<li><a href="http://info.cern.ch/hypertext/WWW/TheProject.html">Browse the first website</a></li>
<li><a href="http://line-mode.cern.ch/www/hypertext/WWW/TheProject.html">Browse the first website using the line-mode browser simulator</a></li>
<li><a href="http://home.web.cern.ch/topics/birth-web">Learn about the birth of the web</a></li>
<li><a href="http://home.web.cern.ch/about">Learn about CERN, the physics laboratory where the web was born</a></li>
</ul>
</body></html>

~$ python3 httpc.py http-textarea.badssl.com
HTTP/1.1 200 OK
Server: nginx/1.10.3 (Ubuntu)
Date: Fri, 20 Jan 2023 16:21:46 GMT
Content-Type: text/html
Content-Length: 713
Last-Modified: Thu, 27 Oct 2022 19:09:20 GMT
Connection: keep-alive
ETag: "635ad760-2c9"
Cache-Control: no-store
Accept-Ranges: bytes

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="shortcut icon" href="/icons/favicon-red.ico"/>
  <link rel="apple-touch-icon" href="/icons/icon-red.png"/>
  <title>textarea.badssl.com</title>
  <link rel="stylesheet" href="/style.css">
  <style>body { background: red; }</style>
</head>
<body>
<style>
#content textarea {
  font-size: 4vw;
}
</style>

<div id="content">
  <h1 style="font-size: 5vw;">
    textarea.<br>badssl.com
  </h1>
  <br><br><br>
  <textarea placeholder="Type here." autofocus></textarea>
</div>

<div id="footer">
  This page contains a <code><textarea></code> input.
</div>

</body>
</html>

Deliverables:

httpc.py
In the lab report, give sample runs (like shown above) of your code for sites info.cern.ch and http-textarea.badssl.com

[30pts] Part 4: HTTP Server

Write a simple HTTP server program https.py. It should listen at port 8000, and supports two following web pages:

index.html (Copy the contents and store them as index.html)
hobby.html (Copy the contents and store them as hobby.html)

When https.py is running on the localhost, the Chrome web browser should show something like the following:

index.html

hobby.html

xxx.html

Tips

You may want to use split and splitlines functions; see the documentation for more detail (search for the words "split" and "splitlines").
You don't need to send optional headers. Only the following items are mandatory:
- HTTP response (The first line).
- Content-Type
- Content-Length
Again, don't use any fancy package; your understanding of how the HTTP protocol works is the big part of lab work.
You will probably need to convert strings to bytes (and vice versa).
You may want to refer to the class notes on how to open a file and read the contents.
Make sure that Chrome navigates your site freely (e.g., clicking a link should work well).
Note that your server should perform the following task repeatedly: accept(), recv(), send(), close(). Use an infinite loop that does the above task.

Deliverables

https.py
Briefly change index.html and hobby.html so that they are associated with you (add your name or something).
In your lab report, give screenhosts of the Chrome browser that show that your server works correctly.

[10pts] Lab Report and Submission

Write a lab report by using the provided template. The writing quality of the lab report matters.

~/bin/submit -c=IT430 -p=lab02 *.py *.html lab02.docx