Hashgraph Hello World

If you’ve heard about Hashgraph and wondering how to get started, here is a little guide based off the docs provided in the SDK. Running the demo is easy but preparing your system can take a little bit of time. (Just like cooking!)

A good place to start is https://www.hederahashgraph.com/ where you can read a bit about it but there is a section for developers which points you to https://dev.hashgraph.com/ which is where the good stuff is.

There is a “How do I get started?” section which is where you … start. The instructions are at: https://dev.hashgraph.com/docs/installation/

Pre flight check list

Step 1: JDK 8

You need at least JDK 8 otherwise you’ll get an error like this:

> cloudnthings$ java -jar swirlds.jar 
> Exception in thread "main" java.lang.UnsupportedClassVersionError: com/swirlds/platform/Browser :
 Unsupported major.minor version 52.0

If you are on a Mac, you want to run:

> java -version
java version "1.8.0_171"
Java(TM) SE Runtime Environment (build 1.8.0_171-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.171-b11, mixed mode)

and make sure you get a response like above. Otherwise go to Oracle and download the Java SE Development Kit.

Go through the installation process and you should see a folder called jdk1.8.0_171.jdk at /Library/Java/JavaVirtualMachines/

Run the java -version command again to verify.

Step 2: JCE Unlimited Policy for Java 8

Next download Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files 8 from here and paste it to /Library/Java/JavaVirtualMachines/jdk1.8.0_161.jdk/Contents/Home/jre/lib/security/policy/unlimited. Otherwise you’ll get this error.

Note: When I tried to do a clean install of Java and repeat the process from scratch I found that I didn’t get this error which is a little strange. I found the 2 files were already at: /Library/Java/JavaVirtualMachines/jdk1.8.0_161.jdk/Contents/Home/jre/lib/security/policy/unlimited

Step 3: Download the SDK

Go to https://www.swirlds.com/download/ and download the SDK, extract it and then navigate to the sdk folder and run the following command in step 4 in a terminal.

Step 4: Run this command

> java -jar swirlds.jar

This is what you should see:

Congrats! You have your first Hashgraph application up and running. This is called the “Stats Demo” and is the default demo that runs when the  > java -jar swirlds.jar command is run or if the swirlds.jar file is double clicked.

It displays basic statistics such as:

• number of corrupted events received per second
• average number of bytes per second transfered during a sync
• number of bytes in the transactions received per second (from unique
• events created by self and others)
• number of bytes in each transactions
• number of events per second created by this node
• number of times a TLS connections was created
• percentage of events received that are already known

This is neat but let’s get the “Hello World” or in this case “Hello Swirlds” app going.

Step 5: Hello Swirlds

Quit the Stats Demo application with command+q or ctrl+c in terminal and open up config.txt

Uncomment by removing the “#” from line 8 “app, HelloSwirldDemo.jar” and re-comment out by typing # in front of line 10 “#app, StatsDemo.jar”. Save the file and then re-run the application and you should get this:

You’ll see I’ve been a bit crafty and changed the name Alice to Seandotau. This was just another simple change in the config.txt file.

Summary

If you had Java 8 and the Java Cryptography Extension already, this demo would have taken only about 5 minutes to spin up. It’s a neat way to see something in action for yourself in a few simple steps. Keep experimenting, and remember, learning is doing!