The unable to resolve external address message is simply debug info, doesn't provide any value. The network is unreachable message is a .NET message and could be the result of any network call. Without knowing which call produced the error it also provides no value. That's why I was asking if you were able to press the Start Local Server button and if any messages showed up in Unity's console. There should certainly be some message specifically as a result of pushing the button. From the info you've provided I have no idea when your error messages show up. Are they there on startup? Do they show up only when you push the button? Do they repeat for each button press?
Anyway, I'm glad you were able to resolve it. Maybe ArenMook can figure out what's going on and add support for your Apple Airport device.
On the topic of stack traces, each message in Unity's console comes with a stack trace: simply click on the message and ctrl+C (or whatever the copy keyboard shortcut is

). You could also set a breakpoint and when hit your IDE / debugger should populate a call stack or stack trace window.
Example from Unity's console:
EditorQuest ShowWindow called
UnityEngine.Debug:Log(Object)
EditorQuest:ShowWindow() (at Assets/Editor/EditorStoryManager/EditorQuestManager/EditorQuest.cs:40)
EditorStoryManager:OnEnable() (at Assets/Editor/EditorStoryManager/EditorStoryManager.cs:112)
UnityEditor.EditorWindow:GetWindow(String, Type[])
EditorStoryManager:ShowWindow() (at Assets/Editor/EditorStoryManager/EditorStoryManager.cs:53)