How configure Rocket Chat and MongoDB in separatelly hosts?

I'm trying to install and configure rocketchat and mongodb in separatelly hosts. One for application and another one for mongodb. I follown this tutorial https://rocket.chat/docs/installation/manual-installation/ubuntu/

and I did all steps for each part separately (mongodb and rocketchat)

when I ran the main.js command:

MONGO_URL=mongodb://<mongodb-ip-host>:27017/rocketchat?replicaSet=rs01 MONGO_OPLOG_URL=mongodb://<mongodb-ip-host>:27017/local?replicaSet=rs01 ROOT_URL=http://0.0.0.0:3000 PORT=3000 node /var/Rocket.Chat/main.js

I got this error below:

                        throw(ex);
                        ^

MongoNetworkError: failed to connect to server [127.0.0.1:27017] on first connect [Error: connect ECONNREFUSED 127.0.0.1:27017
    at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1137:16) {
  name: 'MongoNetworkError',
  errorLabels: [Array],
  [Symbol(mongoErrorContextSymbol)]: {}
}]
    at Pool.<anonymous> (/var/Rocket.Chat/programs/server/npm/node_modules/meteor/npm-mongo/node_modules/mongodb-core/lib/topologies/server.js:431:11)
    at Pool.emit (events.js:311:20)
    at /var/Rocket.Chat/programs/server/npm/node_modules/meteor/npm-mongo/node_modules/mongodb-core/lib/connection/pool.js:557:14
    at /var/Rocket.Chat/programs/server/npm/node_modules/meteor/npm-mongo/node_modules/mongodb-core/lib/connection/connect.js:39:11
    at callback (/var/Rocket.Chat/programs/server/npm/node_modules/meteor/npm-mongo/node_modules/mongodb-core/lib/connection/connect.js:261:5)
    at Socket.<anonymous> (/var/Rocket.Chat/programs/server/npm/node_modules/meteor/npm-mongo/node_modules/mongodb-core/lib/connection/connect.js:286:7)
    at Object.onceWrapper (events.js:418:26)
    at Socket.emit (events.js:311:20)
    at emitErrorNT (internal/streams/destroy.js:92:8)
    at emitErrorAndCloseNT (internal/streams/destroy.js:60:3)
    at processTicksAndRejections (internal/process/task_queues.js:84:21) {
  name: 'MongoNetworkError',
  errorLabels: [ 'TransientTransactionError' ],
  [Symbol(mongoErrorContextSymbol)]: {}
}

PS.: I set the RocketChat on /var/Rocket.Chat folder

I'd like to understand why some part of application are trying to connect in a mongodb locally : 127.0.0.1:27017