Host code

using UnityEngine;
using System.Collections;
using UnityEngine.Networking;
using UnityEngine.Networking.Match;
using Steamworks;
using NATTraversal;

public class SelectHost : Selectable {
    public DestroyOnNetworkConnect manager;
    protected CallResult<LobbyCreated_t> createLobby;
    // Use this for initialization
    void Start () {
    }

    public override void OnSelect ()
    {
        if(SteamManager.Initialized) {
            createLobby = CallResult<LobbyCreated_t>.Create(LobbyCallback);
            print("Creating lobby...");
            var handle = SteamMatchmaking.CreateLobby(ELobbyType.k_ELobbyTypePublic, 4);
            createLobby.Set(handle);
            // Do this on the host in OnCreateMatch() after creating the steam lobby
        } else {
            print("SteamManager not Initialized?");
        }
    }

    private void LobbyCallback(LobbyCreated_t pCallback, bool IOFailure) {
        if(IOFailure) {
            print("IOFailure.");
            return;
        }
        print("Lobby callback successful.");
        string matchName = SteamFriends.GetPersonaName();
        print("Creating lobby under name: " + matchName);
        manager.StartHostAll(matchName, (uint) 4);
        //manager.StartHost();
        print("Setting lobby for reference");
        manager.steamIDLobby = new CSteamID(pCallback.m_ulSteamIDLobby);
        SteamMatchmaking.SetLobbyData(manager.steamIDLobby, "guid", manager.cachedHelper.guid.ToString());
        SteamMatchmaking.SetLobbyData(manager.steamIDLobby, "publicIP", manager.externalIP);
        SteamMatchmaking.SetLobbyData(manager.steamIDLobby, "internalIP", manager.hostInternalIP);
        SteamMatchmaking.SetLobbyData(manager.steamIDLobby, "name", matchName);
    }
}