     coap.sendResponse(ip, port, packet.messageid, (uint8_t *)"1", 1);
 }
 
-void callback_switch(CoapPacket &packet, IPAddress ip, int port) {
-    Serial.println("[Switch]");
-    
-    // send response
-    coap.sendResponse(ip, port, packet.messageid, (uint8_t *)"CLOSE", 5);
-}
-
-
 // CoAP client response callback
 void callback_response(CoapPacket &packet, IPAddress ip, int port) {
     Serial.println("[Coap Response got]");


// CoAP server endpoint url callback
void callback_light(CoapPacket &packet, IPAddress ip, int port);
void callback_switch(CoapPacket &packet, IPAddress ip, int port);

// CoAP client response callback
void callback_response(CoapPacket &packet, IPAddress ip, int port);

void setup() {
    Serial.begin(9600);

    // add server url endpoints.
    // can add multiple endpoint urls.
    // exp) coap.server(callback_switch, "switch");
    //      coap.server(callback_env, "env/temp");
    //      coap.server(callback_env, "env/humidity");
    coap.server(callback_light, "light");

    // client response callback.
    // this endpoint is single callback.
    coap.response(callback_response);

    // start coap server/client
