最近在用node-coap做一个实时推送消息的项目，如果有使用这个库的，可以加群交流一下 142756845

“The Constrained Application Protocol (CoAP) is a specialized web transfer protocol for use with constrained nodes and constrained networks in the Internet of Things. The protocol is designed for machine-to-machine (M2M) applications such as smart energy and building automation.”

COAP可以是一个简化版的HTTP，除此之外还支持客户端observe一个资源的变化，从而实现服务器到客户端的推送。

node-coap库 https://github.com/mcollina/node-coap