File Upload and Messaging Demo

using Ethereum, truffle and Nodejs

This is an Ethereum Blockchain based DApp running on a private network for file sharing through MongoDb server. The app passes encrypted file (AES encryption) hash to another ethereum client on the private ethereum network. This also has a simple message passing facility where the user can just send some messages to another Peer connected on the network. This uses Ethereum Smart Contracts which are deployed in the ethereum private blockchain in the process of setting up of the project. Truffle framework has been used for the web application to work.
MongoDB has been used as the database where we are performing the upload. We are encrypting the given file and returning the sha hash of the encrypted file after the upload in one AJAX (in JQuery) call. We have used ExpressJS and GridFS for the file upload module.

Dependencies

Geth 1.5.9 or above
Truffle 3.2.4
npm 4.2.0
node 7.10.0
MongoDB

Installing dependencies

You can install Geth following the guide from here and Go from here
For Truffle, follow instructions from here
Install npm

$ curl -sL https://deb.nodesource.com/setup_4.x | sudo -E bash - 
$ sudo apt-get install -y nodejs

Install webpack

$ npm install --save-dev webpack

Install web3

$ npm install web3

Install MongoDB by following instructions from here After installations are done, update your system

$ sudo apt-get update 
$ sudo apt-get -y upgrade

Steps

Step 1 : Setting up a geth node

Few things need to be specified in the geth command according to your own system and host details. They are...

RPC port number, Port number, Host address, Location of data directory for your geth accounts and Network id. First initialize the blockchain by adding a Genesis block

geth --rpcport "RPC port number" --rpccorsdomain="*" --rpcaddr "Host address" --rpcapi "eth,web3,db,net,personal" --datadir "Location of data directory" --port "Port number" --networkid "Network id" init ~/docueth/CustomGenesis.json

Example :

geth --rpcport "13080" --rpccorsdomain="*" --rpcaddr "http://ec2-52-53-222-152.us-west-1.compute.amazonaws.com" --rpcapi "eth,web3,db,net,personal" --datadir "/home/ubuntu/mining" --port "13000" --networkid 9866 init ~/docueth/CustomGenesis.json

Then start the geth console

geth --rpcport "13080" --rpccorsdomain="*" --rpcaddr "http://ec2-52-53-222-152.us-west-1.compute.amazonaws.com" --rpcapi "eth,web3,db,net,personal" --datadir "/home/ubuntu/mining" --port "13000" --networkid 9866 console 2>sml.txt

Then in the console, run following commands:

> personal.newAccount("password")

(This will give you the address of your first account. Run this command again to create another account where transactions from other accounts will be received.)

> personal.unlockAccount(eth.accounts[0],"password",60000) 

> admin.startRPC("0.0.0.0",13080)

(13080 is the rpc port number)

> miner.setEtherbase(eth.accounts[0])

Now to add the geth node with which you will be performing transactions, add it's enode address as a peer. The enode address of a node can be found by :

> admin

Then on your console

> admin.addPeer("the enode address of the other node")

Now you can run

> admin.peers

which will show you the other node as your peer. Then start your miner

> miner.start()

Step 2 : Launching the truffle app

Steps to start a truffle project :

Go to the cloned repos and set up the environment for migration

$ nano truffle.js

Change "host" , "port" and "network_id" under "live" to your specifications.

Run the following to compile the original contracts and deploy them to your network

$ truffle compile --network live 
$ truffle migrate --network live

(Here the contract which we will be using can be found at /docueth/contracts/message.sol)

Now that the contracts are up and running, you can test to see if they are working correctly:

$ truffle test --network live

(You can modify the test if you want to , by changing the file in /docueth/test folder) Once the tests are passed you can be sure that the contracts are correctly deployed and running.

Change the host address for the web app Go to "/docueth/app/javascripts" folder and edit line number 108 in the file app.js :

window.web3 = new Web3(new Web3.providers.HttpProvider("http://ec2-52-52-25-62.us-west-1.compute.amazonaws.com:13080"));

inside HttpProvider, put "your_host_address:rpc_port_number".

Change the line number 22 of "index.html" in "/docueth/app" folder:

<form id="myForm" action="your_host_address:3002/upload" method="post" enctype="multipart/form-data" >

Now we build and run the front end application in the app directory

$ npm run build
$ truffle serve --network live --p 15080

(mention the port you want your app to run , by default it runs on 8080)

Open another terminal and start mongodb by

$ sudo service mongodb start 
$ mongo

(mongo console opens up , you can check the database manually)

Open another terminal and goto docueth/upload-gridfs and run

$ node app.js

Check the localhost (or the network address of the running instance ) with the specific port number in a web browser. Go to "http://your_host_address:15080" You can transfer messages from the message box to a particular account id as mentioned in the field or select file and transfer the hash to another account. Click the "Choose File" button to select a file and then press "Submit". After pressing submit the document is uploaded to the mongodb gridfs. You can check the files in the mongodb database by opening the mongo console and type

> use gridfstest 
> db.ctFiles.files.find()