Getting Started with multichainr

The multichainr package provides a high-level R interface to the MultiChain API. This guide walks you through setting up binary paths, creating a temporary test blockchain, connecting to a node, and performing basic cleanup.

1. Setting Up MultiChain Paths

To interact with the blockchain, the package needs to locate the MultiChain executable files (multichaind and multichain-util).

Persistent Configuration (Recommended)

The most convenient way is to set the path in your environment variables. Open your .Renviron file (you can use usethis::edit_r_environ()) and add the following line:

MULTICHAIN_PATH="C:/path/to/multichain"

(Replace the path with the actual directory containing your MultiChain binaries.)

Manual Session Configuration

If you prefer not to use environment variables, you can set the path manually at the beginning of your R script using mc_set_path():

library(multichainr)

# Provide the path to the folder containing MultiChain executables
mc_set_path(Sys.getenv("MULTICHAIN_PATH"))

2. Initializing a Temporary Blockchain

Let’s create a “sandbox” — a temporary blockchain named vignette_chain for testing purposes.

chain_name <- "vignette_chain"

# Initialize a new blockchain (creates the configuration files)
mc_node_init(chain_name)

3. Starting the Node

Once initialized, we can launch the MultiChain node. By default, it starts in daemon mode (background process).

# Start the node
mc_node_start(chain_name)

# Wait a few seconds for the node to initialize and open the RPC port
Sys.sleep(3)

4. Connecting and Running Commands

To communicate with the node, we need to retrieve its configuration (RPC port, username, and password) and create a connection object. multichainr handles this by reading the node’s configuration files automatically.

# Get the configuration for the specific chain
config <- mc_get_config(chain_name)

# Create a connection object
conn <- mc_connect(config)

# Verify the node status
info <- mc_get_info(conn)
cat("Connected to chain:", info$chainname, "\n")
cat("Protocol Version:", info$protocolversion, "\n")
cat("Current Block Height:", info$blocks, "\n")

5. Node Shutdown and Cleanup

After finishing your work, it is important to stop the node and, if the blockchain was temporary, delete its data directory to free up disk space.

# Send the stop signal to the node
mc_node_stop(conn)

# Brief pause to allow the process to finalize file writing
Sys.sleep(2)

# Deleting the blockchain files (WARNING: This is irreversible!)
# Determine the default MultiChain data directory based on the OS
if (.Platform$OS.type == "windows") {
  base_dir <- file.path(Sys.getenv("APPDATA"), "MultiChain")
} else if (Sys.info()["sysname"] == "Darwin") {
  base_dir <- file.path(Sys.getenv("HOME"), "Library/Application Support/MultiChain")
} else {
  base_dir <- file.path(Sys.getenv("HOME"), ".multichain")
}

chain_dir <- file.path(base_dir, chain_name)

if (dir.exists(chain_dir)) {
  unlink(chain_dir, recursive = TRUE)
  message("Temporary blockchain files deleted successfully.")
}

Summary

In this guide, we covered:

1. Configuring the path to MultiChain binaries via MULTICHAIN_PATH or mc_set_path().
2. Initializing and starting a local blockchain node.
3. Establishing an RPC connection.
4. Shutting down the node and cleaning up temporary files.

In the next vignettes, we will explore how to manage assets, issue tokens, and store data in streams.

Key Highlights of this Vignette:

• Environment Variables: It emphasizes the use of MULTICHAIN_PATH, making the user’s workflow much smoother.
• Temporary Sandbox: It teaches best practices by showing how to create and destroy test environments without leaving “ghost” folders in the user’s system.
• Safe Evaluation: The eval = FALSE setting in the first chunk ensures that the vignette can be built into a package website (like pkgdown) even if the server building it doesn’t have MultiChain installed.
• Cross-Platform: The cleanup logic is robust for Windows, macOS, and Linux.