coap-server.c: DTLS server with default credentials for PSK

The example server creates a new endpoint for DTLS-secured traffic.
The secure endpoint is bound to the port number of the unsecure
port plus one (i.e. if the default port number 5683 is used for
cleartext CoAP traffic, the secure port is bound to 5684).

This server uses the credentials "Client_identity" as user name and
"secretPSK" as password for testing. DO NOT USE THIS FOR PRODUCTION.

examples/coap-server.c

@@ -28,6 +28,7 @@
 #include "coap_config.h"
 #include "resource.h"
 #include "coap.h"
+#include "coap_dtls.h"
 
 #ifndef min
 #define min(a,b) ((a) < (b) ? (a) : (b))
@@ -322,6 +323,21 @@ init_resources(coap_context_t *ctx) {
 #endif /* WITHOUT_ASYNC */
 }
 
+static void
+fill_keystore(coap_context_t *ctx) {
+  coap_keystore_item_t *psk;
+  static unsigned char user[] = "Client_identity";
+  size_t user_length = sizeof(user) - 1;
+  static unsigned char key[] = "secretPSK";
+  size_t key_length = sizeof(key) - 1;
+
+  psk = coap_keystore_new_psk(NULL, 0, user, user_length,
+                              key, key_length, 0);
+  if (!psk || !coap_keystore_store_item(ctx->keystore, psk, NULL)) {
+    coap_log(LOG_WARNING, "cannot store key\n");
+  }
+}
+
 static void
 usage( const char *program, const char *version) {
   const char *p;
@@ -347,6 +363,11 @@ get_context(const char *node, const char *port) {
   struct addrinfo hints;
   struct addrinfo *result, *rp;
 
+  ctx = coap_new_context(NULL);
+  if (!ctx) {
+    return NULL;
+  }
+
   memset(&hints, 0, sizeof(struct addrinfo));
   hints.ai_family = AF_UNSPEC;    /* Allow IPv4 or IPv6 */
   hints.ai_socktype = SOCK_DGRAM; /* Coap uses UDP */
@@ -361,16 +382,38 @@ get_context(const char *node, const char *port) {
   /* iterate through results until success */
   for (rp = result; rp != NULL; rp = rp->ai_next) {
     coap_address_t addr;
+    coap_endpoint_t *endpoint;
 
     if (rp->ai_addrlen <= sizeof(addr.addr)) {
       coap_address_init(&addr);
       addr.size = rp->ai_addrlen;
       memcpy(&addr.addr, rp->ai_addr, rp->ai_addrlen);
 
-      ctx = coap_new_context(&addr);
-      if (ctx) {
-        /* TODO: output address:port for successful binding */
+      endpoint = coap_new_endpoint(&addr, COAP_ENDPOINT_NOSEC);
+      if (endpoint) {
+        coap_attach_endpoint(ctx, endpoint);
+
+        if (coap_dtls_is_supported()) {
+          if (addr.addr.sa.sa_family == AF_INET) {
+            addr.addr.sin.sin_port = htons(ntohs(addr.addr.sin.sin_port) + 1);
+          } else if (addr.addr.sa.sa_family == AF_INET6) {
+            addr.addr.sin6.sin6_port =
+              htons(ntohs(addr.addr.sin6.sin6_port) + 1);
+          } else {
+            goto finish;
+          }
+
+          endpoint = coap_new_endpoint(&addr, COAP_ENDPOINT_DTLS);
+          if (endpoint) {
+            coap_attach_endpoint(ctx, endpoint);
+          } else {
+            coap_log(LOG_CRIT, "cannot create DTLS endpoint\n");
+          }
+        }
         goto finish;
+      } else {
+        coap_log(LOG_CRIT, "cannot create endpoint\n");
+        continue;
       }
     }
   }
@@ -487,6 +530,7 @@ main(int argc, char **argv) {
   if (!ctx)
     return -1;
 
+  fill_keystore(ctx);
   init_resources(ctx);
 
   /* join multicast group if requested at command line */