Chatbots in C++: From Theory to Ready Code in One Evening

Introduction: Why C++ for Chatbots Is Not Madness

When it comes to creating chatbots, Python, JavaScript, or Node.js usually come to mind. But what if I told you that C++ can be just as effective a tool for this task? Yes, the same C++ that is associated with drivers, games, and high-load systems.

In fact, chatbots in C++ are an excellent solution when:

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• You need maximum performance (processing thousands of requests per second);
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• You are working in an embedded environment or on microcontrollers;
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• You want to minimize memory consumption;
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• You simply love C++ and want to try something new.
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In this practical guide, we will create a full-fledged chatbot in C++ from scratch. We will use real libraries, write working code, and break down an architecture that will allow your bot to communicate via the Telegram API. By the end of the article, you will have not just theory, but a ready-made project that you can run and expand.

What We Need: Toolkit

Before writing code, let's figure out the tools. For creating a chatbot in C++ we will need:

Libraries

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• libcurl — for HTTP requests (sending and receiving data from the Telegram API);
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• nlohmann/json — a lightweight library for working with JSON (parsing server responses);
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• Boost.Asio (optional) — for asynchronous network operations;
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• Threading support (std::thread) — for processing multiple requests simultaneously.
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Installation (Linux / macOS)

sudo apt-get install libcurl4-openssl-dev  # For Linux\nbrew install curl                          # For macOS

The nlohmann/json library can be included as header-only (just download json.hpp and put it in your project).

Project Structure

telegram_bot/\n├── main.cpp\n├── bot.hpp\n├── bot.cpp\n├── json.hpp\n└── Makefile (or CMakeLists.txt)

Step 1: Bot Skeleton — Working with the Telegram API

The Telegram Bot API is a RESTful API. All we need to do is send HTTP requests to https://api.telegram.org/bot<TOKEN>/METHOD. The most important methods are getUpdates (get new messages) and sendMessage (send a reply).

Let's create a TelegramBot class that will handle all communication.

bot.hpp — Header File

#ifndef BOT_HPP\n#define BOT_HPP\n\n#include <string>\n#include <vector>\n#include <nlohmann/json.hpp>\n\nusing json = nlohmann::json;\n\nclass TelegramBot {\npublic:\n    explicit TelegramBot(const std::string& token);\n    \n    // Get a list of new messages (long polling)\n    std::vector<json> getUpdates(long offset = 0);\n    \n    // Send a text message\n    bool sendMessage(long chat_id, const std::string& text);\n    \n    // Handle a single incoming message\n    std::string handleMessage(const json& message);\n\nprivate:\n    std::string api_url_;\n    std::string httpGet(const std::string& url);\n    std::string httpPost(const std::string& url, const std::string& post_data);\n};\n\n#endif // BOT_HPP

bot.cpp — Implementation

#include "bot.hpp"\n#include <curl/curl.h>\n#include <sstream>\n\n// Callback for writing curl response to a string\nstatic size_t WriteCallback(void* contents, size_t size, size_t nmemb, void* userp) {\n    ((std::string*)userp)->append((char*)contents, size * nmemb);\n    return size * nmemb;\n}\n\nTelegramBot::TelegramBot(const std::string& token) \n    : api_url_("https://api.telegram.org/bot" + token + "/") {}\n\nstd::string TelegramBot::httpGet(const std::