19.0.0 released Nov 08, 2023
Cookies in a web application


A value is entered in the browser and saved as a cookie, then read back later. This example displays a web form. When it is submitted, the input is used to set a cookie in response. Then in a separate page, the cookie value is obtained and displayed. This is the basic mechanism often used in saving web application states and session information.

In a nutshell:  web browser; Apache; Unix sockets; 1 source files, 48 lines of code.
Screenshots of application
A web form is displayed where the user can enter a name. Clicking "Submit" sends it to the server:

Vely

A reply page when the server receives the information and sets the cookie in the browser:

Vely

A request sent to the server will now have the cookie, which the server code will read and display back:

Vely

Setup prerequisites
Install Vely - you can use standard packaging tools such as apt, dnf, pacman or zypper.

Because it is used in this example, you will need to install Apache as a web server.

After installing Vely, turn on syntax highlighting in vim if you're using it:
vv -m

Get the source code
The source code is a part of Vely installation. It is a good idea to create a separate source code directory for each application (and you can name it whatever you like). In this case, unpacking the source code will do that for you:
tar xvf $(vv -o)/examples/cookies.tar.gz
cd cookies

Setup application
The very first step is to create an application. The application will be named "cookies", but you can name it anything (if you do that, change it everywhere). It's simple to do with vf:
sudo vf -i -u $(whoami) cookies

This will create a new application home (which is "/var/lib/vv/cookies") and do the application setup for you. Mostly that means create various subdirectories in the home folder, and assign them privileges. In this case only current user (or the result of "whoami" Linux command) will own those directories with 0700 privileges; it means a secure setup.
Build application
Use vv utility to make the application:
vv -q

Start your application server
To start the application server for your web application use vf FastCGI process manager. The application server will use a Unix socket to communicate with the web server (i.e. a reverse-proxy):
vf -w 3 cookies

This will start 3 daemon processes to serve the incoming requests. You can also start an adaptive server that will increase the number of processes to serve more requests, and gradually reduce the number of processes when they're not needed:
vf cookies

See vf for more options to help you achieve best performance.

If you want to stop your application server:
vf -m quit cookies

Setup web server
This shows how to connect your application listening on a Unix socket (started with vf) to Apache web server.

- Step 1:
To setup Apache as a reverse proxy and connect your application to it, you need to enable FastCGI proxy support, which generally means "proxy" and "proxy_fcgi" modules - this is done only once:
- Step 2:
Edit the Apache configuration file:
Add this to the end of file ("/cookies" is the application path (see request-URL) and "cookies" is your application name):
ProxyPass "/cookies" unix:///var/lib/vv/cookies/sock/sock|fcgi://localhost/cookies

- Step 3:
Finally, restart Apache. On Debian systems (like Ubuntu) or OpenSUSE:
sudo systemctl restart apache2

On Fedora systems (like RedHat) and Arch Linux:
sudo systemctl restart httpd

Note: you must not have any other URL resource that starts with "/cookies" (such as for example "/cookies.html" or "/cookies_something" etc.) as the web server will attempt to pass them as a reverse proxy request, and they will likely not work. If you need to, you can change the application path to be different from "/cookies", see request-URL.

Access application server from the browser
Use the following URL(s) to access your application server from a client like browser (see request-URL). Use actual IP or web address instead of 127.0.0.1 if different.
# Enter cookie 
http://127.0.0.1/cookies/cookies?action=enter_cookie

# Query entered cookie 
http://127.0.0.1/cookies/cookies?action=query_cookie

Note: if your server is on the Internet and it has a firewall, you may need to allow HTTP traffic - see ufw, firewall-cmd etc.
Source files
The following are the source files in this application:
- Working with cookies (cookies.vely)
Usage of cookies is simple - get-cookie is used to obtain the cookie from a web client (i.e. a browser), and set-cookie to set the cookie in the browser when the response is sent back.

Three tasks (based on "action" task parameter) allow user to enter a value that is sent back to the server (see "enter_cookie" as the "action" parameter), which the server then sends back to the browser in response (see "save_cookie"), and finally with "query_cookie" this value can be obtained and displayed again. This demonstrates how server-side software uses cookies to manipulate and obtain the client state.


#include "vely.h"

request-handler /cookies

    task-param action

    if-task "enter_cookie"

        // Display a form to get cookie value
        out-header default
        @<h2>Enter your name</h2>
        @<form action="<<p-path>>/cookies" method="POST">
        @    <input type="hidden" name="action" value="save_cookie">
        @    <label for="cookie_value">Your name:</label><br/>
        @    <input type="text" name="cookie_value" value=""><br/>
        @    <br/>
        @    <input type="submit" value="Submit">
        @</form>

    else-task "save_cookie"

        // Submittal of form: save the cookie through response to the browser
        input-param cookie_value
        get-time to define cookie_expiration year 1 timezone "GMT"
        set-cookie "customer_name" = cookie_value  expires cookie_expiration  path "/"
        out-header default
        @Cookie sent to browser!
        @<hr/>

    else-task "query_cookie"

        // Web request that delivers cookie value back here (to server); display it.
        get-cookie define name="customer_name"
        out-header default
        @Customer name is <<p-web name>>
        @<hr/>

    else-task other
        out-header default
        @Unrecognized action<hr/>
    end-task

end-request-handler

See also
Examples
example-client-API  
example-cookies  
example-create-table  
example-develop-web-applications-in-C-programming-language  
example-distributed-servers  
example-docker  
example-encryption  
example-file-manager  
example-form  
example-hash-server  
example-hello-world  
example-how-to-design-application  
example-how-to-use-regex  
example-json  
example-multitenant-SaaS  
example-postgres-transactions  
examples  
example-sendmail  
example-shopping  
example-stock  
example-uploading-files  
example-using-mariadb-mysql  
example-using-trees-for-in-memory-queries  
example-utility  
example-write-report    
See all
documentation


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