It is true that many header files in UE4 are not very “well-behaved”, that is, they don’t #include or forward-declare things they need.
But Networking.h should be #including everything an order that prevents errors. What errors are you seeing when you use #include “Networking.h”?
If you need to use a long relative path in #include to get compiler to find file, that indicates that build system isn’t recognizing dependency on that module correctly. If “Networking” is in dependency list in your Build.cs file, I’m not sure what could cause this.
“assumed to be int” error is what Visual Studio normally outputs when it encounters an unknown type.