Ticket Machine

A C++23 client-server ticket machine simulation. The project models ticket availability, reservations, purchases, customer data, coin-based payment and change calculation. It contains a console client, a TCP server and reusable domain logic packaged as a CMake library.

Table of Contents

• Overview
• Features
• Tech Stack
• Project Structure
• Requirements
• Build
• Run
• Client Commands
• Data Files
• Configuration
• Troubleshooting

Overview

Ticket Machine is split into two executables:

• ticket-machine-server — loads ticket and cashbox data from JSON, starts a local TCP server and handles ticket operations.
• ticket-machine — interactive console client used to list tickets, reserve a ticket, finalize a purchase or cancel a reservation.

The server keeps track of ticket states and active reservations. Purchases are finalized only when the reservation is valid, the inserted coins cover the ticket price and the machine can return the required change from the available cashbox.

Money values are represented as integer grosz values. For example, 350 means 3.50 PLN.

Features

• Interactive console client.
• TCP-based client-server communication.
• JSON request/response protocol.
• Ticket listing grouped by type and price.
• Ticket reservation with timeout handling.
• Purchase finalization with customer data.
• Coin inventory management.
• Minimal coin change calculation with limited coin availability.
• Automatic refund on failed purchases.
• Seed data loaded from JSON files.
• CMake + Conan build setup.

Tech Stack

• C++23
• CMake 3.25+
• Conan 2
• Asio
• nlohmann/json
• Ninja

Project Structure

.
├── app/
│   ├── main.cpp                # Client entry point
│   └── server_main.cpp         # Server entry point
├── data/
│   ├── server_seed.json        # Default server data
│   ├── 01_happy_path.json      # Standard purchase scenario
│   ├── 02_no_change_possible.json
│   ├── 03_last_ticket_race.json
│   └── 04_exact_payment_focus.json
├── include/
│   ├── change_calculator.hpp
│   ├── coin_inventory.hpp
│   ├── console_client_app.hpp
│   ├── models.hpp
│   ├── network_protocol.hpp
│   ├── paths.hpp
│   ├── server_console_app.hpp
│   ├── server_seed_data.hpp
│   ├── ticket_machine_client.hpp
│   ├── ticket_server.hpp
│   └── ticket_server_host.hpp
├── src/
│   ├── change_calculator.cpp
│   ├── coin_inventory.cpp
│   ├── console_client_app.cpp
│   ├── network_protocol.cpp
│   ├── server_console_app.cpp
│   ├── server_seed_data.cpp
│   ├── ticket_machine_client.cpp
│   ├── ticket_server.cpp
│   └── ticket_server_host.cpp
├── tests/
├── CMakeLists.txt
├── conanfile.py
└── README.md

Requirements

Install the following tools before building the project:

• Conan 2
• CMake 3.25 or newer
• Ninja
• A C++23-capable compiler

On first Conan usage, create or refresh your local Conan profile:

conan profile detect --force

Build

Install dependencies and generate CMake presets:

conan install . -s build_type=Debug -s compiler.cppstd=23 -c tools.cmake.cmaketoolchain:generator=Ninja --build=missing

Configure the project:

cmake --preset conan-debug

Build the project:

cmake --build --preset conan-debug

For a release build, use Release as the build type:

conan install . -s build_type=Release -s compiler.cppstd=23 -c tools.cmake.cmaketoolchain:generator=Ninja --build=missing
cmake --preset conan-release
cmake --build --preset conan-release

Run

Start the server in one terminal:

./build/Debug/ticket-machine-server --port 5555 --data server_seed.json

On Windows, the executable will usually have the .exe extension:

.\build\Debug\ticket-machine-server.exe --port 5555 --data server_seed.json

Start the client in another terminal:

./build/Debug/ticket-machine --host 127.0.0.1 --port 5555

On Windows:

.\build\Debug\ticket-machine.exe --host 127.0.0.1 --port 5555

Then use the interactive prompt:

list
reserve normal
status
buy
cancel
quit

Client Commands

Command	Description
help	Show available client commands.
list	Show available ticket types, prices and counts.
reserve <type>	Reserve one ticket of the selected type, for example reserve normal.
status	Show the currently active reservation.
buy	Finalize the active reservation. The client asks for customer data and inserted coins.
cancel	Cancel the active reservation.
quit / exit	Close the client.

Supported coin denominations are:

1, 2, 5, 10, 20, 50, 100, 200, 500

All denominations are given in grosz.

Data Files

The server loads initial tickets and cashbox state from JSON files located in the data/ directory.

Default file:

data/server_seed.json

Available sample scenarios:

File	Purpose
server_seed.json	Default server state with normal and reduced tickets.
01_happy_path.json	Basic successful purchase scenario.
02_no_change_possible.json	Scenario where the cashbox may not be able to return change.
03_last_ticket_race.json	Scenario focused on a single remaining ticket.
04_exact_payment_focus.json	Scenario with an empty cashbox, useful for exact payment testing.

Example:

./build/Debug/ticket-machine-server --data 02_no_change_possible.json

Relative paths passed to --data are resolved inside the data/ directory. Absolute paths can also be used.

A seed file has the following shape:

{
  "tickets": [
    { "id": 1, "price": 350, "type": "normal", "status": "available" },
    { "id": 2, "price": 170, "type": "reduced", "status": "available" }
  ],
  "cashbox": [
    { "denomination": 200, "count": 1 },
    { "denomination": 100, "count": 5 }
  ]
}

Ticket statuses supported by the seed loader:

available, reserved, sold

Configuration

The server accepts:

ticket-machine-server [--port PORT] [--data FILE_OR_PATH]

The client accepts:

ticket-machine [--host HOST] [--port PORT]

Default values:

Setting	Default
Server port	5555
Client host	127.0.0.1
Client port	5555
Server data file	data/server_seed.json

The CMake project exposes these options:

Option	Default	Description
TICKET_MACHINE_BUILD_CLIENT	ON	Build the ticket-machine executable.
TICKET_MACHINE_BUILD_SERVER	ON	Build the ticket-machine-server executable.

Example: build only the server:

cmake --preset conan-debug -DTICKET_MACHINE_BUILD_CLIENT=OFF
cmake --build --preset conan-debug

Troubleshooting

Preset "conan-debug" not found

Run conan install first. Conan generates the CMake presets used by the build commands.

Ninja is not found

Install Ninja or change the CMake generator passed to Conan:

-c tools.cmake.cmaketoolchain:generator=Ninja

The project is built with the wrong C++ standard

Make sure the Conan install command includes:

-s compiler.cppstd=23

The project requires a C++23-capable compiler.

The client cannot connect to the server

Check that the server is running and that both programs use the same port:

ticket-machine-server --port 5555
ticket-machine --host 127.0.0.1 --port 5555

The server cannot open the data file

Use a filename from the data/ directory, for example:

ticket-machine-server --data server_seed.json

or pass an absolute path to a custom JSON file.