jmg-duarte / btc-handshake

Bitcoin Handshake Demo

Bitcoin Handshake

A PoC implementation of the Bitcoin handshake, performed between two nodes. To simplify connecting to nodes, the implementation takes a DNS seed and gets a list of nodes to connect to and perform the handshake, as shown in the diagram below.

sequenceDiagram
    btc-handshake->>DNSSeed: resolve
    DNSSeed->>btc-handshake: peers
    btc-handshake->>Node: version
    Node->>btc-handshake: version
    btc-handshake->>Node: verack
    Node->>btc-handshake: verack
    Node-->>btc-handshake: (other messages)

Description

The code is split into two parts, the library containing the data structures relating to the protocol, and a CLI tool to actually perform the handshake.

Usage

Usage: btc-handshake [OPTIONS] <DNS_SEED>

Arguments:
  <DNS_SEED>  Bitcoin DNS seed domain

Options:
  -p, --port <PORT>        Target's TCP port [default: 8333]
  -t, --timeout <TIMEOUT>  Handshake timeout, in seconds [default: 5]
  -n, --network <NETWORK>  Target network [default: mainnet] [possible values: mainnet, testnet, testnet3, signet]
  -h, --help               Print help

Example

$ btc-handshake seed.bitcoin.sipa.be.

2024-02-22T19:27:28.069121Z  INFO btc_handshake: Resolving DNS seed: seed.bitcoin.sipa.be.:8333
2024-02-22T19:27:28.193436Z  WARN version{network=Mainnet address=88.198.57.103:8333}: btc_handshake: received version (70015) which is lower than the currently implemented one (70012) trying to proceed
2024-02-22T19:27:28.604618Z  WARN verack{network=Mainnet}: btc_handshake: server skipped verack message
2024-02-22T19:27:33.076413Z  WARN btc_handshake: command mismatch: expected verack got Ok("sendcmpct\0\0\0")
2024-02-22T19:27:33.076653Z  WARN btc_handshake: failed to fill whole buffer
2024-02-22T19:27:33.076683Z  WARN btc_handshake: command mismatch: expected verack got Ok("sendcmpct\0\0\0")
2024-02-22T19:27:33.076711Z  WARN btc_handshake: command mismatch: expected verack got Ok("sendheaders\0")
2024-02-22T19:27:33.076736Z  WARN btc_handshake: command mismatch: expected verack got Ok("sendheaders\0")
2024-02-22T19:27:33.076760Z  WARN btc_handshake: command mismatch: expected verack got Ok("sendcmpct\0\0\0")
2024-02-22T19:27:33.076788Z  WARN btc_handshake: command mismatch: expected verack got Ok("sendcmpct\0\0\0")
2024-02-22T19:27:33.076811Z  WARN btc_handshake: command mismatch: expected verack got Ok("sendheaders\0")
2024-02-22T19:27:33.076834Z  WARN btc_handshake: command mismatch: expected verack got Ok("sendcmpct\0\0\0")
2024-02-22T19:27:33.076860Z  WARN btc_handshake: failed to fill whole buffer
2024-02-22T19:27:33.076884Z  WARN btc_handshake: deadline has elapsed
2024-02-22T19:27:33.076904Z  WARN btc_handshake: command mismatch: expected verack got Ok("sendheaders\0")
2024-02-22T19:27:33.076927Z  WARN btc_handshake: command mismatch: expected verack got Ok("sendcmpct\0\0\0")
2024-02-22T19:27:33.077164Z  WARN btc_handshake: command mismatch: expected verack got Ok("sendheaders\0")
2024-02-22T19:27:33.077270Z  WARN btc_handshake: command mismatch: expected verack got Ok("sendcmpct\0\0\0")
2024-02-22T19:27:33.077295Z  WARN btc_handshake: command mismatch: expected verack got Ok("sendheaders\0")
2024-02-22T19:27:33.077318Z  WARN btc_handshake: command mismatch: expected verack got Ok("sendcmpct\0\0\0")
2024-02-22T19:27:33.077342Z  WARN btc_handshake: command mismatch: expected verack got Ok("sendcmpct\0\0\0")
2024-02-22T19:27:33.077366Z  WARN btc_handshake: command mismatch: expected verack got Ok("sendcmpct\0\0\0")
2024-02-22T19:27:33.077390Z  WARN btc_handshake: command mismatch: expected verack got Ok("sendcmpct\0\0\0")
2024-02-22T19:27:33.077506Z  INFO btc_handshake: finished with 5 SUCCESS & 20 FAILED

As we can see, some clients will skip the verack by sending an empty buffer (marked by server skipped verack message), other clients will ignore the verack and start sending other messagess straight away.

DNS Seeds

Here you can find a list of seeds the official Bitcoin node will attempt to resolve. You can find the list on bitcoin/bitcoin.

seed.bitcoin.sipa.be.
dnsseed.bluematt.me.
dnsseed.bitcoin.dashjr.org.
seed.bitcoinstats.com.
seed.bitcoin.jonasschnelli.ch.
seed.btc.petertodd.net.
seed.bitcoin.sprovoost.nl.
dnsseed.emzy.de.
seed.bitcoin.wiz.biz.