This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
If other machine in same LAN/Network then using url with IP address (IPAddress:8084\app) will work.If you are in same LAN but not able to access url with Ip then there might be some issue in network and you should contact your network/It administrator. If you want to access Url from some other machine (wchich is not in same Lan) then you should host your website/application
The URL "localhost:8084\app" is invalid. The use of a backslash is a convention of Windows filesystem paths. URLs are neither Windows nor are they filesystem paths.
Beyond that, as William said, "localhost" is the address of whatever machine you are directly attached, so if you want to communicate with a different machine, it must have at least 1 external IP address, which can be used directly or by looking up a domain hostname in a resolver such as DNS or a "hosts" file. And, of course, open filewall for port 8084 so that the attempt isn't blocked.
An IDE is no substitute for an Intelligent Developer.