In this lab, you will learn the basics of socket programming for TCP connections in Python: how to create a socket, bind it to a specific address and port, as well as send and receive a HTTP packet. You will also learn some basics of HTTP header format.

You will develop a web server that handles one HTTP request at a time. Your web server should accept and parse the HTTP request, get the requested file from the server’s file system, create an HTTP response message consisting of the requested file preceded by header lines, and then send the response directly to the client. If the requested file is not present in the server, the server should send an HTTP "404 Not Found" message back to the client.

Code

Below you will find the skeleton code for the Web server. You are to complete the skeleton code. The places where you need to fill in code are marked with #Fill in start and #Fill in end. Each place may require one or more lines of code.

Running the Server

Put an HTML file (e. g., HelloWorld. html) in the same directory that the server is in. Run the server program. Determine the IP address of the host that is running the server (e. g., 128.238.251.26). From another host or the same host if you run the server on the local manchine, open a browser and provide the corresponding URL. For example:

http://128.238.251.26:6789/HelloWor ld. html

‘HelloWorld. html’ is the name of the file you placed in the server directory. Note also the use of the port number after the colon. You need to replace this port number with whatever port you have used in the server code. In the above example, we have used the port number 6789. The browser should then display the contents of HelloWorld. html. If you omit ":6789", the browser will assume port 80 and you will get the web page from the server only if your server is listening at port 80.

You can also run the server program on your own PC and access the webserver from the same PC using the IP address for local host (127.0.0.1). For example:

http://127.0.0.1:6789/HelloWorld. html

Then try to get a file that is not present at the server. You should get a "404 Not Found" message.

What to Hand in

You will hand in the complete server code along with the screen shots of your client browser, verifying that you actually receive the contents of the HTML file from the server.
*** the source file (.py) of your web server ***

Skeleton Python Code for the Web Server (Use the code on the next page as the skeleton of your .py file and insert lines of code needed between #Fill in state and #Fill in end. Please note that Python programs get structured through indentation, copy and paste may change the indentation of the following lines. You are suggested to use Python 3.x.

#import socket module

import socket

import sys

serversocket = socket. socket(socket. AF_INET, socket. SOCK_STREAM)

print("Socket Created!!")

try:

#bind the socket

#fill in start

#fill in end

except socket. error as msg:

print("Bind failed. Error Code: " + str(msg[0]) + "Message: " + msg[1])

sys. exit()

print("Socket bind complete")

#start listening on the socket

#fill in start

#fill in end

print('Socket now listening')

while True:

#Establish the connection

connectionSocket, addr = #fill in start #fill in end

print('source address:' + str(addr))

try:

#Receive message from the socket

message = #fill in start #fill in end

print('message = ' + str(message))

#obtian the file name carried by the HTTP request message

filename = message. split()[1]

print('filename = ' + str(filename))

f = open(filename[1:], 'rb')

outputdata = f. read()

#Send the HTTP response header line to the socket

#fill in start

#fill in end

#Send the content of the requested file to the client

connectionSocket. send(outputdata)

#close the connectionSocket

#fill in start

#fill in end

print("Connection closed!")

except IOError:

#Send response message for file not found

#fill in start

#fill in end

#Close the client socket

#fill in start

#fill in end

serverSocket. close()