In one hand, I have a server that I can connect to via Wifi (no Internet). With my browser, I can access the web service by a port number (192.168.x.x). In the other hand, I have a web application that I can access via the browser too on the localhost:port. I would like to access the data that is accessible by the 192.168.x.x port but via the web application. Do I need to add a new service, some new routes?
No you don't need to add new route (you already can connect to web service so all routes already exists).
New service may make your job even harder, because you will need to configure communication between 3 differed applications.
Just edit your web application so it will take data from your web service.