handlerIn = make(chan []byte, 1)
		go func(inbound chan []byte) {
			wg.Wait()
			defer xioutil.SafeClose(handlerIn)
			m.handleInbound(c, inbound, handlerIn)
		}(m.inbound)
	}
	// Fill outbound block.
	// Each token represents a message that can be sent to the client without blocking.
	// The client will refill the tokens as they confirm delivery of the messages.
	for i := 0; i < outboundCap; i++ {