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)
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: 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
$ 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.
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.