For various wireless networks in adversarial environment, jamming attacks against radio channels can severely interfere with the normal network operations or even completely disrupt the network services. In this paper, we propose a new detection and defense method against hostile jamming by using dynamic radio channel allocation (RCA) technique at real-time and without relying on a large amount of data as in the existing methods. Each node independently estimates the normal value of the network throughput. By comparing the operational throughput to the normal value, an abnormal usage of the channel can be found. In this way, the jamming attacks can be detected by monitoring and analyzing the throughput. After detecting the jamming, the defense of the attack is a self-healing approach: switch the jammed channel to one of the available channels by the RCA techniques automatically. The effectiveness of the proposed method has been demonstrated by extensive simulation results.