coaps

CoAPs refers to the secure variant of the Constrained Application Protocol (CoAP). It protects CoAP messages by applying TLS or DTLS as the transport security layer, providing confidentiality, integrity, and authentication between client and server in constrained environments. While CoAP is designed for UDP and low-power devices, CoAPS typically means CoAP over DTLS (the Datagram TLS security profile), most commonly used on UDP port 5684. Unsecured CoAP uses UDP port 5683, but deployments may configure different ports.

Security and operation: CoAP preserves the RESTful semantics of CoAP—requests and responses, confirmable and non-confirmable messages, and features such as observation and resource discovery. When secured, DTLS handles the cryptographic handshake and session management, with authentication possible via pre-shared keys or certificates. DTLS also supports key exchange and renegotiation, though handshake overhead can be a consideration for highly constrained devices. CoAPS traffic is primarily unicast; multicast DTLS support is limited in typical deployments.

Interoperability and alternatives: CoAPS is one way to secure CoAP traffic, but application-layer security mechanisms such as OSCORE (Object Security for Constrained RESTful Environments) can be used on top of CoAP to provide end-to-end security across proxies and intermediaries, independent of the transport layer. Some deployments also explore CoAP over TCP with TLS, but this is a separate approach from the traditional DTLS-based CoAPS over UDP.

Applications: CoAPS is widely used in IoT and constrained networks where secure exchange of resources, commands, and telemetry is required, such as smart homes, industrial automation, and sensor networks.