Since I don't really know the project very well I've kept the refactoring to a minimum. That said: I did implement some changes:
This is unrelated to the port but I had to fix the NetworkHandlerTest in order to build the project and run all tests.
The numbered options in the commandline application start now at 0 and not 1 as before since I used the forEachIndexed function.
I extended the CommandLine#nextLineTrimmed function so that it actually trims the next line.
Nullability was kept down as much as possible, except where the existing Java code dictated otherwise. However there are two places where I had to add non-null asserts (!!) to make everything compile. I've added TODOs to these places so that they can be easily tracked.
There is one test in SystemTest which seemed a bit strange to me. It works perfectly fine and was ported almost 1:1 from Java but I've still added a TODO since I think i might be worth to check whether the test is still valid or not.
Since I don't really know the project very well I've kept the refactoring to a minimum. That said: I did implement some changes:
NetworkHandlerTestin order to build the project and run all tests.forEachIndexedfunction.CommandLine#nextLineTrimmedfunction so that it actually trims the next line.SystemTestwhich seemed a bit strange to me. It works perfectly fine and was ported almost 1:1 from Java but I've still added a TODO since I think i might be worth to check whether the test is still valid or not.