Web Server and how we can design app in C#
- 1. Lecture6- Web Server NET 445 – Internet Programming
- 2. Web Servers 2 Web servers respond to HypertextTransfer Protocol (HTTP) requests from clients and send back a response containing a status code and often content such as HTML, XML or JSON as well. Examples for web servers: Apache and Nginx (linux web servers) Internet Information Services (IIS) ( for windows) Examples for web clients Google Chrome, Firefox, and Microsoft Edge.
- 3. Why are web servers necessary? 3 The server and client speak the standardized language of the World WideWeb. This standard language is why an old Mozilla Netscape browser can still talk to a modern Apache or Nginx web server, even if it cannot properly render the page design like a modern web browser can. The basic language of the Web with the request and response cycle from client to server then server back to client remains the same as it was when theWeb was invented by Tim Berners-Lee at CERN in 1989. Modern browsers and web servers have simply extended the language of the Web to incorporate new standards.
- 4. Web server implementations 4 The conceptual web server idea can be implemented in various ways.The following web server implementations each have varying features, extensions and configurations. The Apache HTTP Server has been the most commonly deployed web server on the Internet for 20+ years. Nginx is the second most commonly used server for the top 100,000 websites and often serves as a reverse proxy for PythonWSGI servers. Caddy is a newcomer to the web server scene and is focused on serving the HTTP/2 protocol with HTTPS.
- 5. What is an HTTP Server? 5 An HTTP web server is nothing but a process that is running on your machine and does exactly two things: Listens for incoming http requests on a specificTCP socket address (IP address and a port number which I will talk about later) Handles this request and sends a response back to the user.
- 6. Simple HTTP Server using Sockets 6 "HTTP/1.0 200 OKnnHello World" Create a Simple Python script open a socket Send a simple request with a message “Hello World”
- 7. Simple HTTP Server using Sockets 7 Simple HTTP Server using Sockets # Define socket host and port SERVER_HOST = "0.0.0.0" SERVER_PORT = 8000 # Create socket server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) server_socket.bind((SERVER_HOST, SERVER_PORT)) server_socket.listen(1) print("Listening on port %s ..." % SERVER_PORT) while True: # Wait for client connections client_connection, client_address = server_socket.accept() # Get the client request request = client_connection.recv(1024).decode() print(request) # Send HTTP response response = "HTTP/1.0 200 OKnnHello World" client_connection.sendall(response.encode()) client_connection.close() # Close socket server_socket.close()
- 8. Simple HTTP Server using http.server 8 Python standard library: http.server comes with a in-built webserver which can be invoked for simple web client server communication. The port number can be assigned programmatically and the web server is accessed through this port. It is not a full featured web server which can parse many kinds of file, it can parse simple static html files and serve them by responding them with required response codes.
- 9. Creating a simple HTML file to serve 9 Creating a simple HTML file to serve Place this file in the local folder <!DOCTYPE html> <html> <body> <h1>This is a web page</h1> <p>NET445 Internet Programming</p> </body> </html>
- 10. Simple HTTP Server using http.server 10 Simple HTTP Server using http.server Place this script next to the HTML file Run the script and open the browser to http://127.0.0.1:8000 import http.server import socketserver PORT = 8000 handler = http.server.SimpleHTTPRequestHandler with socketserver.TCPServer(("", PORT), handler) as httpd: print("Server started at localhost:" + str(PORT)) httpd.serve_forever()
- 11. Flask Web Framework 11 What is Web Framework? represents a collection of libraries and modules that enables a web application developer to write applications without having to bother about low-level details such as protocols, thread management etc. Flask is a web application framework written in Python. It is developed by Armin Ronacher, who leads an international group of Python enthusiasts named Pocco. Flask is based on theWerkzeug WSGI toolkit and Jinja2 template engine. Both are Pocco projects.
- 12. Flask Web Framework 12 WSGI Web Server Gateway Interface (WSGI) has been adopted as a standard for Python web application development. WSGI is a specification for a universal interface between the web server and the web applications. Jinja2 Jinja2 is a popular templating engine for Python. A web templating system combines a template with a certain data source to render dynamic web pages.
- 13. Install Flask 13 You can install flask using this command pip3 install Flask
- 14. First Application in Flask 14 In order to test Flask installation, type the following code in the editor as Hello.py from flask import Flask app = Flask(__name__) @app.route("/") def hello_world(): return "Hello World" if __name__ == "__main__": app.run()
- 15. Simple Application in details 15 Flask constructor takes the name of current module (__name__) as argument. The route() function of the Flask class is a decorator, which tells the application which URL should call the associated function. app.route(rule, options) The rule parameter represents URL binding with the function. The options is a list of parameters to be forwarded to the underlying Rule object. In the above example,‘/’ URL is bound with hello_world() function. Hence, when the home page of web server is opened in browser, the output of this function will be rendered. Finally the run() method of Flask class runs the application on the local development server.
- 16. Flask – Routing 16 URL ‘/net445’ rule is bound to the hello_net445() function. As a result, if a user visits http://localhost:5000/net445 URL, the output of the hello_net445() function will be rendered in the browser. The add_url_rule() function of an application object is also available to bind a URL with a function as in the above example, route() is used. from flask import Flask app = Flask(__name__) @app.route("/") def hello_world(): return "Hello World" @app.route("/net445") def hello_net445(): return "hello Net445" if __name__ == "__main__": app.run()
- 17. Flask – Variable Rules 17 It is possible to build a URL dynamically, by adding variable parts to the rule parameter. This variable part is marked as <variable-name>. It is passed as a keyword argument to the function with which the rule is associated. In the following example, the rule parameter of route() decorator contains <name> variable part attached to URL ‘/hello’. from flask import Flask app = Flask(__name__) @app.route('/hello/<name>') def hello_name(name): return 'Hello %s!' % name if __name__ == '__main__': app.run(debug = True)
- 18. Flask – Variable Rules and Conversions 18 In addition to the default string variable part, rules can be constructed using the following converters − from flask import Flask app = Flask(__name__) @app.route('/blog/<int:postID>') def show_blog(postID): return 'Blog Number %d' % postID @app.route('/rev/<float:revNo>') def revision(revNo): return 'Revision Number %f' % revNo if __name__ == '__main__': app.run() Sr.No. Converters & Description 1 int accepts integer 2 float For floating point value 3 path accepts slashes used as directory separator character
- 19. Flask – Templates 19 Flask will try to find the HTML file in the templates folder, in the same folder in which this script is present. Application folder Hello.py templates hello.html
- 20. jinja2 – Templates 20 A web template contains HTML syntax interspersed placeholders for variables and expressions (in these case Python expressions) which are replaced values when the template is rendered. The following code is saved as hello.html in the templates folder. <!doctype html> <html> <body> <h1>Hello {{ name }}!</h1> </body> </html>
- 21. Simple Template in Flask 21 You can install flask using this command from flask import Flask, render_template app = Flask(__name__) @app.route('/hello/<user>') def hello_name(user): return render_template('hello.html', name = user) if __name__ == '__main__': app.run(debug = True)
- 22. jinja2 – Templates 22 The jinja2 template engine uses the following delimiters for escaping from HTML. {% ... %} for Statements {{ ... }} for Expressions to print to the template output {# ... #} for Comments not included in the template output # ... ## for Line Statements
- 23. Advanced Template – HTML code 23 named results.html <!doctype html> <html> <body> <table border = 1> {% for key, value in result.items() %} <tr> <th> {{ key }} </th> <td> {{ value }} </td> </tr> {% endfor %} </table> </body> </html>
- 24. Advanced Template – Python Code 24 Advanced Template – Python Code from flask import Flask, render_template app = Flask(__name__) @app.route('/result') def result(): dict = {'phy':50,'che':60,'maths':70} return render_template('results.html', result = dict) if __name__ == '__main__': app.run(debug = True)
- 25. References: Foundations of Python Network ProgrammingThird Edition by Brandon Rhodes (2014) James F. Kurose, and KeithW Ross, Computer Networking:A Top-Down Approach,6th Edition Python 3 documentation https://wiki.python.org/moin/UdpCommunicat ion https://www.w3schools.com/python/ https://www.tutorialspoint.com/python/ 25