Have installed in ubuntu 16.04 LTS, but when open localhost:3000 is not loading

When I start node main.js as per the documents, I got the following output in the terminal, When I open the browser and type http://localhost:3000 it is not loading.

I am using Ubuntu 16.04 LTS,
Node: v8.10.0
Mongodb: 3.4

I don’t know what i am doing wrong, please help

Will load cache for users
1 records load from users
Will load cache for rocketchat_room
1 records load from rocketchat_room
Will load cache for rocketchat_subscription
0 records load from rocketchat_subscription
Will load cache for rocketchat_settings
628 records load from rocketchat_settings
Updating process.env.MAIL_URL
Will load cache for rocketchat_permissions
75 records load from rocketchat_permissions
Will load cache for rocketchat_roles
11 records load from rocketchat_roles
Starting Email Intercepter…
Warning: connect.session() MemoryStore is not
designed for a production environment, as it will leak
memory, and will not scale past a single process.
LocalStore: store created at
LocalStore: store created at
Setting default file store to GridFS
connect deprecated multipart: use parser (multiparty, busboy, formidable) npm module instead npm/node_modules/connect/lib/middleware/bodyParser.js:56:20
connect deprecated limit: Restrict request size at location of read npm/node_modules/connect/lib/middleware/multipart.js:86:15
{“line”:“152”,“file”:“rocketchat_migrations.js”,“message”:“Migrations: Not migrating, already at version 107”,“time”:{"$date":1522248611079},“level”:“info”}
Using GridFS for custom sounds storage
Using GridFS for custom emoji storage
Updating process.env.MAIL_URL
Exception in callback of async function: Error: Invalid PORT specified
at Object.exports.main.argv (/home/javi/Rocket.Chat/programs/server/packages/webapp.js:963:15)
at /home/javi/Rocket.Chat/programs/server/boot.js:459:27
at /home/javi/Rocket.Chat/programs/server/boot.js:473:5
at Function.run (/home/javi/Rocket.Chat/programs/server/profile.js:510:12)
at /home/javi/Rocket.Chat/programs/server/boot.js:470:11

➔ System ➔ startup
➔ ±---------------------------------------------+
➔ ±---------------------------------------------+
➔ | |
➔ | Rocket.Chat Version: 0.62.2 |
➔ | NodeJS Version: 8.10.0 - x64 |
➔ | Platform: linux |
➔ | Process Port: undefined |
➔ | Site URL: http://localhost:3000 |
➔ | ReplicaSet OpLog: Enabled |
➔ | Commit Hash: 07f0e3f |
➔ | Commit Branch: HEAD |
➔ | |
➔ ±---------------------------------------------+

Looks like you are specifying PORT=‘something here’ Make sure you set a proper port number. Otherwise this will happen.