As IoT (Internet of Things) devices become pervasive in our surroundings, it is more important for them to dynamically discover and interact with nearby IoT devices. However, as interaction protocols are often updated without backward compatibility, interaction opportunities between smart objects may disappear. To overcome this, we can apply existing works which try to adapt one interaction protocol to another at runtime, assuming their specifications are given. However, they cannot generate a valid adapter if the specification of the updated protocol syntax is not available. Automatic protocol reverse engineering methods can extract protocol message syntax without prior knowledge, but they cannot be applied to a runtime scenario. In this paper, we propose SeM2Bit, an efficient protocol message inference scheme which adapts a legacy protocol's message based on protocol domain knowledge. Iterative message adaptations make a legacy protocol agent interact with its updated but incompatible version at runtime and have a meaningful interaction without the corresponding specification. The experiment result shows that the use of knowledge is effective to make a meaningful interaction between the incompatible versions with a reasonably small number of message adaptations. (C) 2019 Elsevier B.V. All rights reserved.