Tag Archives: testing

How to Build Your Own Blockchain Part 2 — Syncing Chains From Different Nodes

Welcome to part 2 of the JackBlockChain, where I write some code to introduce the ability for different nodes to communicate.

Initially my goal was to write about nodes syncing up and talking with each other, along with mining and broadcasting their winning blocks to other nodes.   In the end, I realized that the amount of code and explanation to accomplish all of that was way too big for one post. Because of this, I decided to make part 2 only about nodes beginning the process of talking for the future.

By reading this you’ll get a sense of what I did and how I did it. But you won’t be seeing all the code. There’s so much code involved that if you’re looking for my total implementation you should look at the entire code on the part-2 branch on Github.

Like all programming, I didn’t write the following code in order. I had different ideas, tried different tactics, deleted some code, wrote some more, deleted that code, and then ended up with the following.

This is totally fine! I wanted to mention my process so people reading this don’t always think that someone who writes about programming does it in the sequence they write about it. If it were easy to do, I’d really like to write about different things I tried, bugs I had that weren’t simple to fix, parts where I was stuck and didn’t easily know how to move forward.

It’s difficult to explain the full process and I assume most people reading this aren’t looking to know how people program, they want to see the code and implementation. Just keep in mind that programming is very rarely in a sequence.

Twitter, contact, and feel free to use comments below to yell at me, tell me what I did wrong, or tell me how helpful this was. Big fan of feedback.

Other Posts in This Series


If you’re looking to learn about how blockchain mining works, you’re not going to learn it here. For now, read part 1 where I talk about it initially, and wait for more parts of this project where I go into more advanced mining.

At the end, I’ll show the way to create nodes which, when running, will ask other nodes what blockchain they’re using, and be able to store it locally to be used when they start mining. That’s it. Why is this post so long? Because there is so much involved in building up the code to make it easier to work with for this application and for the future.

That being said, the syncing here isn’t super advanced. I go over improving the classes involved in the chain, testing the new features, creating other nodes simply, and finally a way for nodes to sync when they start running.

For these sections, I talk about the code and then paste the code, so get ready.

Expanding Block and adding Chain class

This project is a great example of the benefits of Object Oriented Programming. In this section, I’m going to start talking about the changes to the Block class, and then go in to the creation of the Chain class.

The big keys for Blocks are:

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