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.
The go-coap provides servers and clients for DTLS, TCP-TLS, UDP, TCP in golang language.
- CoAP over UDP RFC 7252.
- CoAP over TCP/TLS RFC 8232
- Observe resources in CoAP RFC 7641
- Block-wise transfers in CoAP RFC 7959
- request multiplexer
- multicast
- CoAP NoResponse option in CoAP RFC 7967
- CoAP over DTLS pion/dtls
- Too many requests response code RFC 8516
- Go 1.20 or higher
// Server // Middleware function, which will be called for each request. func loggingMiddleware(next mux.Handler) mux.Handler { return mux.HandlerFunc(func(w mux.ResponseWriter, r *mux.Message) { log.Printf("ClientAddress %v, %v\n", w.Conn().RemoteAddr(), r.String()) next.ServeCOAP(w, r) }) } // See /examples/simple/server/main.go func handleA(w mux.ResponseWriter, req *mux.Message) { err := w.SetResponse(codes.GET, message.TextPlain, bytes.NewReader([]byte("hello world"))) if err != nil { log.Printf("cannot set response: %v", err) } } func main() { r := mux.NewRouter() r.Use(loggingMiddleware) r.Handle("/a", mux.HandlerFunc(handleA)) r.Handle("/b", mux.HandlerFunc(handleB)) log.Fatal(coap.ListenAndServe("udp", ":5688", r)) // for tcp // log.Fatal(coap.ListenAndServe("tcp", ":5688", r)) // for tcp-tls // log.Fatal(coap.ListenAndServeTLS("tcp", ":5688", &tls.Config{...}, r)) // for udp-dtls // log.Fatal(coap.ListenAndServeDTLS("udp", ":5688", &dtls.Config{...}, r)) } // Client // See /examples/simpler/client/main.go func main() { co, err := udp.Dial("localhost:5688") // for tcp // co, err := tcp.Dial("localhost:5688") // for tcp-tls // co, err := tcp.Dial("localhost:5688", tcp.WithTLS(&tls.Config{...})) // for dtls // co, err := dtls.Dial("localhost:5688", &dtls.Config{...})) if err != nil { log.Fatalf("Error dialing: %v", err) } ctx, cancel := context.WithTimeout(context.Background(), time.Second) defer cancel() resp, err := co.Get(ctx, "/a") if err != nil { log.Fatalf("Cannot get response: %v", err) return } log.Printf("Response: %+v", resp) }Server example.
Client example.
Server example.
Client example.
Apache 2.0
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