December 20, 2016

Simple HTTP Server and Client in Python

Introduction about how a simple http server and client works under the hood.
http server

This time I’d like to show you how to make a simple HTTP server and client in python. It’s a bit different from other tutorials I’ve ever wrote and I’d like to say that I’m also a beginner in python. But, I’ll try to make sure you understand what I wrote because this tutorial is easy.

First, you need to know what HTTP is. Definition of HTTP based on wikipedia:

The Hypertext Transfer Protocol (HTTP) is an application protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web.
HTTP definition based on Wikipedia.

In simple words, HTTP is a protocol that used for world wide web communication. So, if you’re browsing the web, downloading data, and hosting a website, you’re using HTTP protocol. There are many web server software that support HTTP protocol such as apache, nginx, and lighttpd. This time, you’re so lucky because I’ll show you how to make something like that (a simple version of course) in python language.

Step 1: Write HTTP server script using BaseHTTPServer module

Luckily, python provides us an HTTP server module, it’s called BaseHTTPServer. We use two classes from this module, namely BaseHTTPRequestHandler and HTTPServer. We also need to use os module to access file in your system.

First, we need to import those modules:

#!/usr/bin/env python

from BaseHTTPServer import BaseHTTPRequestHandler, HTTPServer
import os

Next, write a custom class namely KodeFunHTTPRequestHandler that implement BaseHTTPRequestHandler.

#Create custom HTTPRequestHandler class
class KodeFunHTTPRequestHandler(BaseHTTPRequestHandler):

In this tutorial, I just implement GET command from HTTP. To do that, we need to override do_GET() function. Our objective is to request an HTML file from server using our client (explained int the next step). Script inside do_GET() function is written to handle our objective.

#handle GET command
def do_GET(self):
rootdir = ‘c:/xampp/htdocs/’ #file location
try:
if self.path.endswith(‘.html’):
f = open(rootdir + self.path) #open requested file

#send code 200 response
self.send_response(200)

#send header first
self.send_header(‘Content-type’,‘text-html’)
self.end_headers()

#send file content to client
self.wfile.write(f.read())
f.close()
return

except IOError:
self.send_error(404, ‘file not found’)

Finally, add following script to run the server:

def run():
print(‘http server is starting…’)

#ip and port of server
#by default http server port is 80
server_address = (‘127.0.0.1’, 80)
httpd = HTTPServer(server_address, KodeFunHTTPRequestHandler)
print(‘http server is running…’)
httpd.serve_forever()

if name == ‘main‘:
run()

Save it and name it whatever you want (e.g, kodefun-httpserver.py). Here is the complete script of http server:

#!/usr/bin/env python

from BaseHTTPServer import BaseHTTPRequestHandler, HTTPServer
import os

#Create custom HTTPRequestHandler class
class KodeFunHTTPRequestHandler(BaseHTTPRequestHandler):

#handle GET command
def do_GET(self):
rootdir = ‘c:/xampp/htdocs/’ #file location
try:
if self.path.endswith(‘.html’):
f = open(rootdir + self.path) #open requested file

#send code 200 response
self.send_response(200)

#send header first
self.send_header(‘Content-type’,‘text-html’)
self.end_headers()

#send file content to client
self.wfile.write(f.read())
f.close()
return

except IOError:
self.send_error(404, ‘file not found’)

def run():
print(‘http server is starting…’)

#ip and port of servr
#by default http server port is 80
server_address = (‘127.0.0.1’, 80)
httpd = HTTPServer(server_address, KodeFunHTTPRequestHandler)
print(‘http server is running…’)
httpd.serve_forever()

if name == ‘main‘:
run()

Step 2: Write a simple HTTP client

To check if our server is working fine, we need an HTTP client. You can use your web browser to do this. But, It’ll be cool if you make your own client. To accomplish this, let’s make another script, let’s name it kodefun-httpclient.py. Copy following script to your file:

#!/usr/bin/env python

import httplib
import sys

#get http server ip
http_server = sys.argv[1]
#create a connection
conn = httplib.HTTPConnection(http_server)

while 1:
cmd = raw_input(‘input command (ex. GET index.html): ‘)
cmd = cmd.split()

if cmd[0] == ‘exit’: #tipe exit to end it
break

#request command to server
conn.request(cmd[0], cmd[1])

#get response from server
rsp = conn.getresponse()

#print server response and data
print(rsp.status, rsp.reason)
data_received = rsp.read()
print(data_received)

conn.close()

Step 3: Test using GET command

The final step, we’ll test is our scripts above work just fine. To run the server, type the following command in your command prompt or terminal:

$ python kodefun-httpserver.py

If there is no problem, you’ll see “http server is running…”. Next, we need to create a dummy HTML file, let’s call it dummy.html and copy the code below:

<head>
<title>Dummy HTML</title>
</head>
<body>
<h1>Kode Fun is Awesome</h1>
<h1>You’re awesome</h1>
</body>

Save it to your root folder defined in your script. In this example I use c:/xampp/htdocs/. Next, we need to run the client, type following command to run the client:

$ python kodefun-httpclient.py 127.0.0.1

When the client is running type following code to get dummy.html file:

$ GET dummy.html

If there is no problem, and it should be no problem, you’ll see the content of dummy.html file.

That’s all I can do this time. See you on my next tutorial.

Downloads

Get completed project here.

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