m.disconnect("handler blocked", true)
	}
}

func (m *muxServer) unblockSend(seq uint32) {
	if !m.checkSeq(seq) {
		return
	}
	m.recvMu.Lock()
	defer m.recvMu.Unlock()
	if m.outBlock == nil {
		// Closed
		return
	}
	select {
	case m.outBlock <- struct{}{}:
	default:
		gridLogIf(m.ctx, errors.New("output unblocked overflow"))
	}
}

func (m *muxServer) ping(seq uint32) pongMsg {

	// OpMuxServerMsg contains a message to a server Mux
	OpMuxServerMsg

	// OpUnblockSrvMux contains a message that a server mux is unblocked with one.
	// Only Stateful streams has flow control.
	OpUnblockSrvMux

	// OpUnblockClMux contains a message that a client mux is unblocked with one.
	// Only Stateful streams has flow control.
	OpUnblockClMux

	// OpAckMux acknowledges a mux was created.
	OpAckMux

		t.Error("unexpected unblocking")
	case <-time.After(100 * time.Millisecond):
	}

	// unlock
	if err = dupl.Close(); err != nil {
		t.Fatal(err)
	}

	// the previously blocked routine should be unblocked
	select {
	case <-locked:
	case <-time.After(1 * time.Second):
		t.Error("unexpected blocking")
	}