attachment-sendfile

Sendfile -- Attachment

This CorDapp shows how to upload and download an attachment via flow.

Concepts

In this CorDapp, there are two parties:

• Seller: sends an invoice (with attachment) to Buyer
• Buyer: receives the invoice and downloads the attached zip file to their local machine

States

You'll want to take a quick look at InvoiceState.kt (path: contracts/src/main/kotlin/net/corda/samples/sendfile/states/InvoiceState.kt)

@BelongsToContract(InvoiceContract::class)
data class InvoiceState(
        val invoiceAttachmentID: String,
        override val participants: List<AbstractParty> = listOf()) : ContractState

Flows

There are two flows sendAttachmentand downloadAttachment.

The flow logic is the following:

• sendAttachment: send and sync the attachment between parties

  1. Uploading attachment from local
  2. Attaching the attachmentID to the transaction
  3. Storing the attached file into attachment service at the counterparty's node (Automatically check if it already exists or not. If it does, do nothing; if not, download the attached file from the conterparty.)

• downloadAttachment: save the attachment file from node's serviceHub to local

  1. signing the attachment service in the node to download the file via attachmentID

Usage

Pre-Requisites

Set up for CorDapp development

Deploy and run the node

./gradlew clean build deployNodes
./build/node/runnodes

Once all 3 nodes have started up, run the following command in the Seller's interactive node shell:

flow start SendAttachment receiver: Buyer

Upon completion of this flow, we have now successfully:

1. uploaded a zip file to Seller's node
2. sent the zip file to Buyer's node

Now, lets move to Buyer's interactive node shell, and run:

flow start DownloadAttachment sender: Seller, path: file.zip

This command is telling the node to retrieve the attachment from the transaction that is sent by Seller and download it as file.zip at the node root direction. (path: build/nodes/Buyer/file.zip)

Notes:

• This uploaded file is hardcoded into the flow.
• The transaction retrieving is also hardcoded to retrieve the first state that being stored in the vault.