include:links-onepage.adoc == Exercises

Using either bitcoin-cli in your terminal, or a Jupyter notebook in conjunction with the TestShell class from the Bitcoin Core Test Framework, try to complete the following exercises.

Changes to the codebase will require you to re-compile afterwards.

Don’t forget to use the compiled binaries found in your source directory, for example /home/user/bitcoin/src/bitcoind, otherwise your system might select a previously-installed (non-modified) version of bitcoind.

1. Make manual connections

   • Add the following configuration options to a new Bitcoin Core node running on signet to have it start it with no connections:

     signet=1
     dnsseed=0
     fixedseeds=0
     debug=addrman

   • Find the (only!) Signet DNS seeder node (in the SigNetParams class starting with "seed") and using a terminal poll this seed node for an address to connect to.

     You can use dig or nslookup to retrieve seeds from the DNS seeder from the DNS seeders.

     If you try this with the mainnet seeds you will need to consider which service flags the seeder advertises support for. For example, if a seed node advertises x1 support this means they return IP addresses of nodes advertizing the NODE_NETWORK service flag. You could query these from sipa’s mainnet seeder by prepending x1 to the subdomain e.g. nslookup x1.seeder.bitcoin.sipa.be

   • Check how many addresses are known to your node: bitcoin-cli -signet getnodeaddresses 0 | jq length

   • Using one of the addresses returned from the previous exercise, connect to this node using the addnode RPC.

   • Observe new addresses being received and connected to in the bitcoind terminal or $DATADIR/debug.log file.

   • What dangers can there be in retrieving node addresses in this way?

   • Is this more of less safe than using the hardcoded seeds? Can you think of a better way to distribute seeds to new users?