Echo

Overview

The Echo application is a simple implementation that demonstrates the basic functionalities of the framework. It receives a message, processes it, and sends back the message as a notice, report, and voucher. This document outlines how to use the Echo application, including sending inputs and inspecting outputs. You can find the source code in the CrabRolls repository.

Usage

With the application running, to use it you need to send a message to the application. The message can be sent using the send command of the Cartesi CLI tool. The following example demonstrates how to send a message to the Echo application:

cartesi send generic --input='Hi Crabrolls!'

The application will process the message and send back the message as a notice, report, and voucher. The following example demonstrates how to get the outputs of the application:

curl 'http://localhost:8080/graphql' -H 'Content-Type: application/json' -d '{"query":"query getLastEntries { inputs(last: 1) { edges { node { notices(last: 1) { edges { node { index payload } } } reports(last: 1) { edges { node { index payload } } } vouchers(last: 1) { edges { node { index payload destination } } } } } } }"}' | jq

this will return the last entries of the application, including the notice, report, and voucher:

{
  "data": {
    "inputs": {
      "edges": [
        {
          "node": {
            "notices": {
              "edges": [
                {
                  "node": {
                    "index": 0,
                    "payload": "0x48692043726162726f6c6c7321"
                  }
                }
              ]
            },
            "reports": {
              "edges": [
                {
                  "node": {
                    "index": 0,
                    "payload": "0x48692043726162726f6c6c7321"
                  }
                }
              ]
            },
            "vouchers": {
              "edges": [
                {
                  "node": {
                    "index": 0,
                    "payload": "0x48692043726162726f6c6c7321",
                    "destination": "0xdeadbeefdeadbeefdeadbeefdeadbeefdeadbeef"
                  }
                }
              ]
            }
          }
        }
      ]
    }
  }
}

And that’s it! You have successfully used the Echo application to send and receive messages, now you can decode the response payload 0x48692043726162726f6c6c7321 using the command cast from foundry:

cast to-ascii 0x48692043726162726f6c6c7321

This will return the message:

Hi Crabrolls!