Recent advances in wireless technologies and electronic devices have enabled the development of low-cost and large-scale wireless sensor networks. Many recent studies have targeted wireless sensor networks, but forwarding messages while satisfying both delay and reliability constraints remains an unsatisfied goal. Although most existing proposals aim at resiliency in multi-hop networks, improvement of network performance such as throughput and latency, and load balancing, supporting multiple forwarding strategies satisfying various demands is not discussed. We propose a forwarding method for messages with delay and reliability constraints on a single wireless sensor network. We evaluate message loss rate by using computer simulation and by implementing the proposed method on actual sensor nodes. Our results show that the proposed method achieves lower message loss rate for messages with delay and reliability constraints than that for best-efforts messages on a network with error-prone wireless links.