CMPUT 404

Create a tcp client, proxy server, echo server in Python. Understand how sockets work in relation to web requests. Use multiprocessing for forking new processes.

Answers to the questions should be submitted to Lab: TCP Proxy on eClass.

• Python socket documentation
• w3 HTTP 1.0 Specification
  • Also good: Intro to HTTP 1.0

Sockets

Create a github repository for this lab and initialize a clean Python3 virtual environment.

1. Make a file called client.py which uses the socket library to connect to www.google.com and requests a page.

2. Make your program output whatever was sent to it onto the terminal.

   • Question 1: How do you specify a TCP socket in Python?

3. Make a file called echo_server.py that listens for incoming connections and echos any received data.

   • Test echoing example: $ echo "Foobar" | nc localhost 8001 -q 1 should return Foobar, provided the port used is 8001

   • Question 2: What is the difference between a client socket and a server socket in Python?

4. Print out information about what is connected to the server socket to the terminal.

   • Question 3: How do we instruct the OS to let us reuse the same bind port?

   • Question 4: What information do we get about incoming connections?

5. Print out whatever is sent to your server program.

   • Question 5: What is returned by recv() from the server after it is done sending the HTTP request?

6. Create a file called proxy_server.py and connect to Google. Create a file called proxy_client.py and connect to your proxy server.

7. Forward whatever is received on the server socket to www.google.com. Take the response from www.google.com and send it to the original connection.

8. Make your proxy server and echo server forking so multiple programs can use it simultaneously.

9. Push your code to GitHub.

   • Question 6: Provide a link to your code on GitHub.