Client app for HTTP communication with web server

made by: Daniel Ghindea - 325CB

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Dependencies

The program uses nlohman/json library for JSON parsing.

Also, during development, the server at 34.246.184.49 was used to test communications, but it may currently be down.

MAKEFILE

    $ make run   # compile & run executable
    $ make clean # cleanup

Description

Client app receives commands from standard input to interact with the web server. When a command is given, the program sends an HTTP request to the server & receives a response that is displayed.

List of commands:

• register - create a user account
• login
• enter_library - request access to the library
• get_books - list a summary of all available books
• get_book - list the details of a specific book
• add_book
• delete_book
• logout
• exit - end the execution

About

Program's functionalities are encapsulated in client_http class. Its arguments store client's username, password and access token and the principal method, run_client(), implements an infinite loop where commands are read from standard input. Depending on the given input, additional data may be read and the method that corresponds to the action is called.

The functionalities for HTTP communication are implemented in http_communication class. It contains methods that compute GET, POST & DELETE requests and methods that realize the communication with the server through sockets.

Every action-related method work as it follows:

• a string that represents the message request is formed according to the desired action
• send_to_server() method is called with message as parameter
• the returned string is interpreted; if the HTTP request was successful a success message or the returned data is displayed, otherwise an error message is displayed.

HTTP protocol

HTTP request protocol is implemented with the help of sockets. To request, update and delete data from the server GET, POST & DELETE methods are used.

• register:

POST /api/v1/tema/auth/register HTTP/1.1
Host: 34.246.184.49
Content-Type: application/json
Content-Length: 38

{"username":"README","password":"123"}

• login:

POST /api/v1/tema/auth/login HTTP/1.1
Host: 34.246.184.49
Content-Type: application/json
Content-Length: 38

{"username":"README","password":"123"}

HTTP response from server contains a session cookie that is stored in its corresponding attribute while the program runs.

• access:

GET /api/v1/tema/library/access HTTP/1.1
Host: 34.246.184.49
Cookie: connect.sid=s%3AuAHUePO_ndfL6jfbpalzR7BEq07jxzIi.ucbnWjM6xVHLoy3QVoHPPVtZJYzfvs9Mqqw7zyTkXT8; Path=/; HttpOnly

HTTP response from server contains an access token that is stored in its corresponding attribute.

• other commands are implemented similarly by including the access token in the header "Authorization: Bearer " + access_token

*check define.h for macros *get_JSON_credentials() returns the credentials of the user as a string in JSON format ({"username":"gigi","password":"1234"})

JSON parsing

The program uses nlohman/json library for JSON parsing. The library is included in the project as a header file. It was used to parse the JSON response from the server and extract the necessary information.

    rc = req.receive_from_server();
    json token = json::parse(strstr(rc, "{"));

    if (!token["token"].empty()) {
        access_token = token["token"];
        MSG(true, "Access granted");
    } else {
        MSG(false, "Access denied");
    }

Checker

To run the checker run this command

    python3 checker/checker.py --script ALL ./client  # run all tests
    python3 checker/checker.py --help     # for more details

Bibliography & tools

• lab
• postman