{"id":1958,"date":"2018-06-17T23:23:32","date_gmt":"2018-06-17T23:23:32","guid":{"rendered":"http:\/\/www.talkcrypto.org\/blog\/?p=1958"},"modified":"2018-06-17T23:35:40","modified_gmt":"2018-06-17T23:35:40","slug":"hello-world-hashgraph-raspberry-pi","status":"publish","type":"post","link":"https:\/\/www.talkcrypto.org\/blog\/2018\/06\/17\/hello-world-hashgraph-raspberry-pi\/","title":{"rendered":"Hello World Hashgraph Raspberry Pi"},"content":{"rendered":"

If you have a Raspberry Pi lying around and fancy seeing if you can get the Hashgraph sdk running on it, here is how.<\/p>\n

Step 1: Check if Java is present and if it is 1.8+<\/h3>\n

If you are running Raspbian Stretch, it will have Java 8 already on it. Otherwise you’ll have to download it at\u00a0\u00a0Oracle<\/a><\/p>\n

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The location of Java on the Pi is:\u00a0\/usr\/lib\/jvm\/jdk-8-oracle-arm32-vfp-hflt<\/span><\/p>\n

Step 2: Get the sdk<\/h3>\n

Run:
\n> wget\u00a0https:\/\/www.swirlds.com\/downloads\/Swirlds%20SDK%20-%20version%2018.05.23.zip<\/code>
\nIf you try running the sdk:<\/p>\n

> jav -jar swirlds.jar<\/code><\/p>\n

and get this error:<\/p>\n

The JAVA_HOME environment variable is not defined correctly<\/span>\r\nThis environment variable is needed to run this program<\/span>\r\nNB: JAVA_HOME should point to a JDK not a JRE\r\n<\/span><\/pre>\n
Make sure you have set JAVA_HOME correctly. To set it run:<\/p>\n
> nano ~\/.profile<\/code>
\nand add this line at the bottom of the file:
\nexport JAVA_HOME=\/usr\/lib\/jvm\/jdk-8-oracle-arm32-vfp-hflt<\/code>
\nTake care of arm32<\/em>\u00a0if you copied the command from another website.<\/p>\n
Test by running:
\n> echo $JAVA_HOME
\n>\u00a0\/usr\/lib\/jvm\/jdk-8-oracle-arm32-vfp-hflt<\/code><\/p>\n
Step 3: Download JCE<\/h3>\n
If you try and run it now, you’ll probably get this error:<\/p>\n
***************************************************************************<\/span>\r\n* ERROR: Please install the Oracle JCE Unlimited Jurisdiction Policy files.<\/span>\r\n* They can be downloaded as a single .zip file from:<\/span>\r\n* \u00a0 \u00a0 <\/span>http:\/\/www.oracle.com\/technetwork\/java\/javase\/downloads\/jce8-download-2133166.html<\/span>\r\n* If that address doesn't work, then click on the DOWNLOAD button <\/span>\r\n* next to the JCE Unlimited Strength link in the Additional Resources <\/span>\r\n* section of this page:<\/span>\r\n* \u00a0 \u00a0 <\/span>http:\/\/www.oracle.com\/technetwork\/java\/javase\/downloads<\/span>\r\n* Then unzip the downloaded .zip file, and move the two .jar files into:<\/span>\r\n*\u00a0 \u00a0 \u00a0 <\/span>\/home\/pi\/Downloads\/sdk\/usr\/lib\/jvm\/jdk-8-oracle-arm32-vfp-hflt\/jre\/lib\/security<\/span>\r\n* Please make sure they are legal in your country before installing.<\/span>\r\n***************************************************************************<\/span><\/pre>\n
Download\u00a0Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files 8 from here<\/a>\u00a0and paste it to \/usr\/lib\/jvm\/jdk-8-oracle-arm32-vfp-hflt\/jre\/lib\/security<\/span>.<\/p>\n
Now it should work but you’ll get null pointer exception errors.<\/p>\n
\"\"<\/p>\n
This is because the code is trying to execute\u00a0console<\/span>.<\/span>out<\/span>.println(<\/span>“Hello Swirld from “ + <\/span>myName<\/span>);\u00a0<\/span><\/em>at line 68 and it can’t because there is no console. Go into the source file and comment this out with \/\/. Do this for line 91 as well.\u00a0<\/span><\/p>\n
Now it should work but\u00a0you won’t see anything happening. If you run top, you should see Java consume 200% cpu but that is about it.\u00a0The problem is that you’ve ssh’d into your Pi and there is no output console. To see some output, try step 4.<\/p>\n
Step 4: Getting funky<\/h3>\n
Go to sdk\/source\/HelloSwirldDemo\/src and modify\u00a0HelloSwirldDemoMain.java and add a system.out.println as shown below.<\/p>\n
#console.out.println(\"Hello Swirld from \" + myName);
\nSystem.out.println(\"Hello Swirld from \" + myName);<\/code><\/p>\n
Step 5: Installing Maven<\/h3>\n
Check if you have maven with:<\/p>\n
pi@raspberrypi:~ $ mvn -v
\nApache Maven 3.5.3 (3383c37e1f9e9b3bc3df5050c29c8aff9f295297; 2018-02-24T19:49:05Z)
\nMaven home: \/opt\/apache-maven-3.5.3
\nJava version: 1.8.0_65, vendor: Oracle Corporation
\nJava home: \/usr\/lib\/jvm\/jdk-8-oracle-arm32-vfp-hflt\/jre
\nDefault locale: en_GB, platform encoding: UTF-8
\nOS name: \"linux\", version: \"4.9.59-v7+\", arch: \"arm\", family: \"unix\"<\/code><\/p>\n
If you don’t get the above then download Maven first:
\n> wget http:\/\/www-us.apache.org\/dist\/maven\/maven-3\/3.5.3\/binaries\/apache-maven-3.5.3-bin.tar.gz<\/code>
\nExtract to \/opt:<\/p>\n
> cd \/opt
\n> sudo tar -xzvf \/path\/to\/apache-maven-3.5.3-bin.tar.gz<\/code><\/p>\n
Then you need to tell shell where to find maven. We\u2019ll do this in the system profile settings so it is available to all users.<\/p>\n
> sudoedit \/etc\/profile.d\/maven.sh<\/code><\/p>\n
and enter<\/p>\n
export M2_HOME=\/opt\/apache-maven-3.2.5
\nexport PATH=$PATH:$M2_HOME\/bin<\/code><\/p>\n
Source:\u00a0https:\/\/xianic.net\/2015\/02\/21\/installing-maven-on-the-raspberry-pi\/<\/p>\n
Step 6: Compiling with Maven<\/h3>\n
Go back to the HelloSwirldDemo folder where there is a pom.xml file. Run:<\/p>\n
mvn install<\/code><\/p>\n
It can take anywhere between 20 seconds to 7 minutes….<\/p>\n
\"\"<\/p>\n
Output<\/p>\n
\"\"<\/p>\n
Here is a quick video sped up 20x:<\/p>\n