How LocalTunnel will start application and deploy, I am not able to understand how localtunnel will know the script to start application and deploy it

I am new in node js I have developed small node REST service now I want deploy this application on server, I have downloaded and used localtunnel but I am not able to understand how localtunnel will start application and deploy it, I have run command 'lt --port 3000' and it successfully ran and deployed on specific url, when I hit URL from browser it is giving in error 504 so then I started to wonder the actual process to start application in localtunnel. I was not sure whether application is started or not or what is happening behind the scene. my package.json

{ "name": "nodeserver", "version": "1.0.0", "description": "test APi", "main": "app.js", "scripts": { "start": "node app.js", "test": "echo \"Error: no test specified\" && exit 1" }, "author": "vivek", "license": "ISC", "dependencies": { "body-parser": "^1.17.1", "express": "^4.15.2", "jsonfile": "^2.4.0", "mongoose": "^4.9.6" } }

Thanks

via user3667921