GoInGameSystem.cs

using Unity.Collections;
using Unity.Entities;
using Unity.NetCode;

namespace Samples.HelloNetcode
{
    // Place any established network connection in-game so ghost snapshot sync can start
    [UpdateInGroup(typeof(HelloNetcodeSystemGroup))]
    [WorldSystemFilter(WorldSystemFilterFlags.ClientSimulation | WorldSystemFilterFlags.ServerSimulation | WorldSystemFilterFlags.ThinClientSimulation)]
    public partial class GoInGameSystem : SystemBase
    {
        private EntityQuery m_NewConnections;

        protected override void OnCreate()
        {
            RequireForUpdate<EnableGoInGame>();
            RequireForUpdate(m_NewConnections);
        }

        protected override void OnUpdate()
        {
            var commandBuffer = new EntityCommandBuffer(Allocator.Temp);
            FixedString32Bytes worldName = World.Name;
            // Go in game as soon as we have a connection set up (connection network ID has been set)
            Entities.WithName("NewConnectionsGoInGame").WithStoreEntityQueryInField(ref m_NewConnections).WithNone<NetworkStreamInGame>().ForEach(
                (Entity ent, in NetworkId id) =>
                {
                    UnityEngine.Debug.Log($"[{worldName}] Go in game connection {id.Value}");
                    commandBuffer.AddComponent<NetworkStreamInGame>(ent);
                }).Run();
            commandBuffer.Playback(EntityManager);
        }
    }
}