Bitcoin Dev Quickstart

This step-by-step tutorial provides a hands-on walkthrough for quickly getting up and running with Bitcoin basics, from a developer's perspective. From building and installation of the headless Bitcoin daemon (bitcoind), interacting with it using the command line, and building a demo C++ application that can send RPC commands and process responses.

The tutorial is written for Ubuntu 18.04. Adjust accordingly for your own environment.

Preliminary Steps

1. Install Prerequisites

Install the following dependencies.

sudo apt install openssl autoconf automake libboost-dev libboost-all-dev libevent-dev

sudo add-apt-repository ppa:bitcoin/bitcoin
sudo apt-get update
sudo apt-get install libdb4.8-dev libdb4.8++-dev

2. Clone the bitcoin repository and change into its directory

$ git clone https://github.com/bitcoin/bitcoin.git
$ cd bitcoin

3. Configure the build

$ ./autogen.sh && ./configure

4. Building and installing the project

$ make -j4 && sudo make install

5. Check the installation

$ which bitcoind

Example response:

/usr/local/bin/bitcoind

$ which bitcoin-cli

Example response:

/usr/local/bin/bitcoin-cli

Configure the Daemon

1. Download a sample configuration file

$ wget https://raw.githubusercontent.com/bitcoin/bitcoin/master/share/examples/bitcoin.conf -O ~/.bitcoin/bitcoin.conf

2. Generate a user and password

$ ./share/rpcauth/rpcauth.py user

Example response:

String to be appended to bitcoin.conf:
rpcauth=user:bf2a249c8580766a1e4fcd9f777533b0$700645074a2f4a4ffd35cf1ec7ada6d8f148053ca4be729c3f54e63ce4664a2e
Your password:
l-sHsqLHrstIh1ZuOVIDjaLcRuYn-Xoy8prVgjboRnc=

NOTE: Record your password for later use.

3. Open ~/.bitcoin/bitcoin.conf, and search for the following (or similar) line:

# You can even add multiple entries of these to the server conf file, and client can use any of them:
# rpcauth=bob:b2dd077cb54591a2f3139e69a897ac$4e71f08d48b4347cf8eff3815c0e25ae2e9a4340474079f55705f40574f4ec99

4. Below that line, add the rpcauth information generated by rpcauth.py.

Example:

rpcauth=user:bf2a249c8580766a1e4fcd9f777533b0$700645074a2f4a4ffd35cf1ec7ada6d8f148053ca4be729c3f54e63ce4664a2e

Running and Testing bitcoind

1. Start the daemon

$ bitcoind -daemon

Example response:

Bitcoin Core starting

2. Show help

$ bitcoind -?

3. Test CLI commands

$ bitcoin-cli -getinfo

Example response:

{
  "version": 209900,
  "blocks": 156419,
  "headers": 641060,
  "verificationprogress": 0.003607647832804664,
  "timeoffset": -1,
  "connections": 10,
  "proxy": "",
  "difficulty": 1090715.680051267,
  "chain": "main",
  "keypoolsize": 1000,
  "paytxfee": 0.00000000,
  "balance": 0.00000000,
  "relayfee": 0.00001000,
  "warnings": "This is a pre-release test build - use at your own risk - do not use for mining or merchant applications"
}

4. Stopping the daemon

bitcoin-cli stop

NOTE: If you may see the following error message if running commands too quickly after starting bitcoind:

error code: -28
error message:
Loading block index..

If you see this kind of error, wait another second or two and try again.

The RPC Interface

1. Start the daemon (if stopped).

$ bitcoind -daemon

2. Use the following curl command to test communication with the the RPC interface.

$ curl --user user --data-binary '{"jsonrpc": "1.0", "id":"curltest", "method": "getblockchaininfo", "params": [] }' -H 'content-type: text/plain;' http://127.0.0.1:8332

Example response:

Enter host password for user 'user':

3. Enter or paste the password generated earlier (e.g. l-sHsqLHrstIh1ZuOVIDjaLcRuYn-Xoy8prVgjboRnc=)

Example response:

{"result":{"chain":"main","blocks":229810,"headers":641062,"bestblockhash":"000000000000019606fe717e1ec8832aadd0b531a9fdb3fc9b66d4396e4c0e6c","difficulty":6695826.282596251,"mediantime":1365171545,"verificationprogress":0.02829406551238997,"initialblockdownload":true,"chainwork":"0000000000000000000000000000000000000000000000340a2573e03179ff18","size_on_disk":7956125601,"pruned":false,"softforks":{"bip34":{"type":"buried","active":true,"height":227931},"bip66":{"type":"buried","active":false,"height":363725},"bip65":{"type":"buried","active":false,"height":388381},"csv":{"type":"buried","active":false,"height":419328},"segwit":{"type":"buried","active":false,"height":481824}},"warnings":"This is a pre-release test build - use at your own risk - do not use for mining or merchant applications"},"error":null,"id":"curltest"}

Demo Example C++

1. Install the following:

$ sudo apt install libcurlpp-dev libcurl4-openssl-dev

2. Create a file called main.cpp:

#include <curlpp/cURLpp.hpp>
#include <curlpp/Easy.hpp>
#include <curlpp/Options.hpp>

#include <string>
#include <sstream>
#include <iostream>

using namespace curlpp::options;

int main(int argc, char *argv[])
{

    if(argc < 3) {
    std::cerr << argv[0] << ": Wrong number of arguments" << std::endl 
	      << "Usage: " << argv[0] << " username password"
	      << std::endl;
    return EXIT_FAILURE;
    }

    std::string username(argv[1]);
    std::string password(argv[2]);

    std::string userpass = username + ":" + password;

    try
	{

		curlpp::Cleanup btcCleanup;

		curlpp::Easy btcRequest;

        std::list<std::string> header; 
        header.push_back("Content-Type: application/json"); 
    
        btcRequest.setOpt(new curlpp::options::HttpHeader(header)); 

        // Set the daemon's URL.
        curlpp::options::Url btcUrl(std::string("http://127.0.0.1:8332"));

        // Set the username and password.
        curlpp::options::UserPwd usrPsswd(userpass);

        // Create the data payload
        std::string json = R"({"jsonrpc": "1.0", "id":"curltest", "method": "getblockchaininfo", "params": [] })";

        // Add options to the request
        btcRequest.setOpt(btcUrl);
        btcRequest.setOpt(usrPsswd);
        btcRequest.setOpt(curlpp::options::PostFields(json));
	    btcRequest.setOpt(curlpp::options::PostFieldSize(json.size()));

		// Send the request 
		btcRequest.perform();
	}

	catch(curlpp::RuntimeError & e)
	{
		std::cout << e.what() << std::endl;
	}

	catch(curlpp::LogicError & e)
	{
        // Result is sent to standard output.
		std::cout << e.what() << std::endl;
	}
    
  return 0;

}

3. Build the demo application:

$ g++ -Wall main.cpp -o btctest -Llib/x86_64-linux-gnu -lcurlpp -Wl,-Bsymbolic-functions -Wl,-z,relro -lcurl -Iinclude -I/usr/include/x86_64-linux-gnu

4. Run the demo with your username and password as command line arguements. Example:

./btctest user l-sHsqLHrstIh1ZuOVIDjaLcRuYn-Xoy8prVgjboRnc=

Example response:

{"result":{"chain":"main","blocks":303520,"headers":641075,"bestblockhash":"000000000000000024450e52f5d08622114b503713243aab15f3f7f989e76267","difficulty":10455720138.48484,"mediantime":1401561878,"verificationprogress":0.07238580672791109,"initialblockdownload":true,"chainwork":"000000000000000000000000000000000000000000007829790f458ed3674540","size_on_disk":22091527638,"pruned":false,"softforks":{"bip34":{"type":"buried","active":true,"height":227931},"bip66":{"type":"buried","active":false,"height":363725},"bip65":{"type":"buried","active":false,"height":388381},"csv":{"type":"buried","active":false,"height":419328},"segwit":{"type":"buried","active":false,"height":481824}},"warnings":"This is a pre-release test build - use at your own risk - do not use for mining or merchant applications"},"error":null,"id":"curltest"}

Congratulations!

You have successfully installed and run the Bitcoin bitcoind daemon, and created a command line application to interact with it to fetch information.

Next steps:

Use bitcoin-cli -rpcwait help to find other RPC calls to add to the application.