InvalidOperationException: Failed to bind socket to [Address Ip=127.0.0.1 Port=9999]

I'm getting

InvalidOperationException: Failed to bind socket to [Address Ip=127.0.0.1 Port=9999]

on a standalone client when trying to connect to a dedicated/headless server, I'll put the code snippets I'm using for server/client below, but would love any advice on what I might be doing wrong here...


var result = await runner.StartGame(new StartGameArgs { Address = NetAddress.LocalhostIPv4(port: 9999), GameMode = GameMode.Server, Scene = sceneIndex, SceneObjectProvider = NetworkSceneManager.Instance });

_runner.StartGame(new StartGameArgs { Address = NetAddress.LocalhostIPv4(port: 9999), GameMode = GameMode.Client, SceneObjectProvider = NetworkSceneManager.Instance });