// may be on user thread
        private NetSenderChannelBase CreateSenderChannel(NetMessageType tp)
        {
            NetSenderChannelBase chan;

            lock (m_sendChannels)
            {
                NetDeliveryMethod method = NetUtility.GetDeliveryMethod(tp);
                int sequenceChannel      = (int)tp - (int)method;

                int channelSlot = (int)method - 1 + sequenceChannel;
                if (m_sendChannels[channelSlot] != null)
                {
                    // we were pre-empted by another call to this method
                    chan = m_sendChannels[channelSlot];
                }
                else
                {
                    switch (method)
                    {
                    case NetDeliveryMethod.Unreliable:
                    case NetDeliveryMethod.UnreliableSequenced:
                        chan = new NetUnreliableSenderChannel(this, NetUtility.GetWindowSize(method), method);
                        break;

                    case NetDeliveryMethod.ReliableOrdered:
                        chan = new NetReliableSenderChannel(this, NetUtility.GetWindowSize(method));
                        break;

                    case NetDeliveryMethod.ReliableSequenced:
                    case NetDeliveryMethod.ReliableUnordered:
                    default:
                        chan = new NetReliableSenderChannel(this, NetUtility.GetWindowSize(method));
                        break;
                    }
                    m_sendChannels[channelSlot] = chan;
                }
            }

            return(chan);
        }