Tutorial 1: Creating and Starting a libp2p Node

This tutorial will guide you through the basics of creating, configuring, starting, and stopping a libp2p node using the Logos libp2p module.

What is libp2p?

libp2p is a modular networking stack for building peer-to-peer applications. It provides transport-agnostic connectivity, peer identity, stream multiplexing, secure channels, and content routing — everything you need to build a decentralized network.

The logos-libp2p-module wraps nim-libp2p's C bindings into a C++ class called Libp2pModuleImpl that you can embed directly into your application.

Step 1: Include the module header and instantiate a node

Every program starts by including the module's single public header - "plugin.h":

#include <cstdio>
#include <string>
#include "plugin.h"

int main()
{
    printf("=== Tutorial 1: Creating and Starting a libp2p Node ===\n\n");

    setLogLevel("fatal");

The main class we work with is Libp2pModuleImpl. Let's create one with default options:

    // Create a libp2p node with default configuration.
    // By default it listens on 127.0.0.1 with a random port (tcp/0).
    Libp2pModuleImpl node;

    printf("Node object created (not yet started)\n");

Step 2: Start the node

Calling start() creates the libp2p context, binds the configured address, and begins accepting connections.

    StdLogosResult startRes = node.start();
    if (!startRes.success) {
        fprintf(stderr, "Failed to start node: %s\n",
                startRes.error.c_str());
        return 1;
    }

    printf("Node started successfully!\n");

Step 3: Query node information

Once the node is running, we can inspect its identity and network addresses using peerInfo().

    StdLogosResult info = node.peerInfo();
    if (!info.success) {
        fprintf(stderr, "Failed to get peer info: %s\n",
                info.error.c_str());
        return 1;
    }

    // Extract the peer ID — a unique cryptographic identifier
    std::string peerId = info.value["peerId"].get<std::string>();
    printf("Peer ID: %s\n", peerId.c_str());

    // List all multiaddresses the node is listening on
    printf("Listening addresses:\n");
    for (const auto& addr : info.value["addrs"]) {
        printf("  %s\n", addr.get<std::string>().c_str());
    }

We can also query specific fields using getNodeInfo():

    StdLogosResult version = node.getNodeInfo("Version");
    if (!version.success) {
        fprintf(stderr, "Failed to get module version: %s\n",
                version.error.c_str());
        return 1;
    }
    printf("Module version: %s\n",
           version.value.get<std::string>().c_str());

    StdLogosResult peerIdResult = node.getNodeInfo("PeerId");
    if (!peerIdResult.success) {
        fprintf(stderr, "Failed to get peer ID: %s\n",
                peerIdResult.error.c_str());
        return 1;
    }
    printf("Peer ID (via getNodeInfo): %s\n",
           peerIdResult.value.get<std::string>().c_str());

Step 4: Stop the node

Always clean up by stopping the node when you're done.

    node.stop();
    printf("Node stopped\n");

    printf("\n=== Tutorial 1 Complete ===\n");

    return 0;
}

Summary

In this tutorial you learned how to:

Create a Libp2pModuleImpl instance
Start and stop a libp2p node
Query peer identity and listening addresses
Retrieve module metadata

Run tutorial

./build/tutorial/tutorial_1_node_lifecycle

← Introduction and Common Patterns | Custom Node Configuration →

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