diff --git a/core/include/ten_runtime/addon/extension/extension.h b/core/include/ten_runtime/addon/extension/extension.h
index f0ac09f5f..489bc10ef 100644
--- a/core/include/ten_runtime/addon/extension/extension.h
+++ b/core/include/ten_runtime/addon/extension/extension.h
@@ -25,12 +25,12 @@ TEN_RUNTIME_API ten_addon_host_t *ten_addon_register_extension(
 
 TEN_RUNTIME_API ten_addon_t *ten_addon_unregister_extension(const char *name);
 
-TEN_RUNTIME_API bool ten_addon_create_extension_async(
+TEN_RUNTIME_API bool ten_addon_create_extension(
     ten_env_t *ten_env, const char *addon_name, const char *instance_name,
     ten_env_addon_on_create_instance_async_cb_t cb, void *user_data,
     ten_error_t *err);
 
-TEN_RUNTIME_API bool ten_addon_destroy_extension_async(
+TEN_RUNTIME_API bool ten_addon_destroy_extension(
     ten_env_t *ten_env, ten_extension_t *extension,
     ten_env_addon_on_destroy_instance_async_cb_t cb, void *user_data,
     ten_error_t *err);
diff --git a/core/include/ten_runtime/binding/cpp/internal/ten_env.h b/core/include/ten_runtime/binding/cpp/internal/ten_env.h
index a6c17eac4..f1bb0cdf9 100644
--- a/core/include/ten_runtime/binding/cpp/internal/ten_env.h
+++ b/core/include/ten_runtime/binding/cpp/internal/ten_env.h
@@ -894,13 +894,13 @@ class ten_env_t {
                                     addon_create_extension_async_cb_t &&cb,
                                     error_t *err) {
     if (cb == nullptr) {
-      return ten_addon_create_extension_async(
+      return ten_addon_create_extension(
           c_ten_env, addon_name, instance_name, nullptr, nullptr,
           err != nullptr ? err->get_internal_representation() : nullptr);
     } else {
       auto *cb_ptr = new addon_create_extension_async_cb_t(std::move(cb));
 
-      return ten_addon_create_extension_async(
+      return ten_addon_create_extension(
           c_ten_env, addon_name, instance_name,
           proxy_addon_create_extension_async_cb, cb_ptr,
           err != nullptr ? err->get_internal_representation() : nullptr);
diff --git a/core/include/ten_runtime/binding/cpp/internal/ten_env_impl.h b/core/include/ten_runtime/binding/cpp/internal/ten_env_impl.h
index 618b1aac2..787b5d8c6 100644
--- a/core/include/ten_runtime/binding/cpp/internal/ten_env_impl.h
+++ b/core/include/ten_runtime/binding/cpp/internal/ten_env_impl.h
@@ -68,13 +68,13 @@ inline bool ten_env_t::addon_destroy_extension_async(
     ten::extension_t *extension, addon_destroy_extension_async_cb_t &&cb,
     error_t *err) {
   if (cb == nullptr) {
-    return ten_addon_destroy_extension_async(
+    return ten_addon_destroy_extension(
         c_ten_env, extension->get_c_extension(), nullptr, nullptr,
         err != nullptr ? err->get_internal_representation() : nullptr);
   } else {
     auto *cb_ptr = new addon_destroy_extension_async_cb_t(std::move(cb));
 
-    return ten_addon_destroy_extension_async(
+    return ten_addon_destroy_extension(
         c_ten_env, extension->get_c_extension(),
         proxy_addon_destroy_extension_async_cb, cb_ptr,
         err != nullptr ? err->get_internal_representation() : nullptr);
diff --git a/core/include_internal/ten_runtime/addon/extension_group/extension_group.h b/core/include_internal/ten_runtime/addon/extension_group/extension_group.h
index 86bea44f5..e806356e2 100644
--- a/core/include_internal/ten_runtime/addon/extension_group/extension_group.h
+++ b/core/include_internal/ten_runtime/addon/extension_group/extension_group.h
@@ -17,10 +17,10 @@ typedef struct ten_addon_store_t ten_addon_store_t;
 
 TEN_RUNTIME_PRIVATE_API ten_addon_store_t *ten_extension_group_get_store(void);
 
-TEN_RUNTIME_API bool ten_addon_extension_group_create(
+TEN_RUNTIME_API bool ten_addon_create_extension_group(
     ten_env_t *ten_env, const char *addon_name, const char *instance_name,
     ten_env_addon_on_create_instance_async_cb_t cb, void *user_data);
 
-TEN_RUNTIME_API bool ten_addon_extension_group_destroy(
+TEN_RUNTIME_API bool ten_addon_destroy_extension_group(
     ten_env_t *ten_env, ten_extension_group_t *extension_group,
     ten_env_addon_on_destroy_instance_async_cb_t cb, void *user_data);
diff --git a/core/include_internal/ten_runtime/addon/protocol/protocol.h b/core/include_internal/ten_runtime/addon/protocol/protocol.h
index 2e9fc5a10..c377b00ca 100644
--- a/core/include_internal/ten_runtime/addon/protocol/protocol.h
+++ b/core/include_internal/ten_runtime/addon/protocol/protocol.h
@@ -27,11 +27,16 @@ typedef struct ten_addon_create_protocol_info_t {
   void *user_data;
 } ten_addon_create_protocol_info_t;
 
-TEN_RUNTIME_PRIVATE_API bool ten_addon_create_protocol_async(
+TEN_RUNTIME_PRIVATE_API bool ten_addon_create_protocol_with_uri(
     ten_env_t *ten_env, const char *uri, TEN_PROTOCOL_ROLE role,
     ten_env_addon_on_create_protocol_async_cb_t cb, void *user_data,
     ten_error_t *err);
 
+TEN_RUNTIME_PRIVATE_API bool ten_addon_create_protocol(
+    ten_env_t *ten_env, const char *addon_name, const char *instance_name,
+    TEN_PROTOCOL_ROLE role, ten_env_addon_on_create_protocol_async_cb_t cb,
+    void *user_data, ten_error_t *err);
+
 TEN_RUNTIME_PRIVATE_API ten_addon_store_t *ten_protocol_get_store(void);
 
 TEN_RUNTIME_PRIVATE_API ten_addon_host_t *ten_addon_protocol_find(
diff --git a/core/src/ten_runtime/addon/extension/extension.c b/core/src/ten_runtime/addon/extension/extension.c
index 129d5fda5..c2886bff8 100644
--- a/core/src/ten_runtime/addon/extension/extension.c
+++ b/core/src/ten_runtime/addon/extension/extension.c
@@ -26,10 +26,10 @@ static ten_addon_store_t g_extension_store = {
 
 ten_addon_store_t *ten_extension_get_store(void) { return &g_extension_store; }
 
-bool ten_addon_create_extension_async(
-    ten_env_t *ten_env, const char *addon_name, const char *instance_name,
-    ten_env_addon_on_create_instance_async_cb_t cb, void *cb_data,
-    TEN_UNUSED ten_error_t *err) {
+bool ten_addon_create_extension(ten_env_t *ten_env, const char *addon_name,
+                                const char *instance_name,
+                                ten_env_addon_on_create_instance_async_cb_t cb,
+                                void *cb_data, TEN_UNUSED ten_error_t *err) {
   TEN_ASSERT(addon_name && instance_name, "Should not happen.");
 
   TEN_ASSERT(ten_env, "Invalid argument.");
@@ -70,7 +70,7 @@ bool ten_addon_create_extension_async(
   }
 }
 
-bool ten_addon_destroy_extension_async(
+bool ten_addon_destroy_extension(
     ten_env_t *ten_env, ten_extension_t *extension,
     ten_env_addon_on_destroy_instance_async_cb_t cb, void *cb_data,
     TEN_UNUSED ten_error_t *err) {
diff --git a/core/src/ten_runtime/addon/extension_group/extension_group.c b/core/src/ten_runtime/addon/extension_group/extension_group.c
index 980498c45..6963004a3 100644
--- a/core/src/ten_runtime/addon/extension_group/extension_group.c
+++ b/core/src/ten_runtime/addon/extension_group/extension_group.c
@@ -50,7 +50,7 @@ ten_addon_t *ten_addon_unregister_extension_group(const char *name) {
   return ten_addon_unregister(ten_extension_group_get_store(), name);
 }
 
-bool ten_addon_extension_group_create(
+bool ten_addon_create_extension_group(
     ten_env_t *ten_env, const char *addon_name, const char *instance_name,
     ten_env_addon_on_create_instance_async_cb_t cb, void *user_data) {
   TEN_ASSERT(addon_name && instance_name, "Should not happen.");
@@ -74,7 +74,7 @@ bool ten_addon_extension_group_create(
                                          user_data);
 }
 
-bool ten_addon_extension_group_destroy(
+bool ten_addon_destroy_extension_group(
     ten_env_t *ten_env, ten_extension_group_t *extension_group,
     ten_env_addon_on_destroy_instance_async_cb_t cb, void *cb_data) {
   TEN_ASSERT(ten_env && ten_env_check_integrity(ten_env, true) && cb,
diff --git a/core/src/ten_runtime/addon/protocol/protocol.c b/core/src/ten_runtime/addon/protocol/protocol.c
index 1d571a8ac..18523dbf4 100644
--- a/core/src/ten_runtime/addon/protocol/protocol.c
+++ b/core/src/ten_runtime/addon/protocol/protocol.c
@@ -113,14 +113,19 @@ ten_addon_host_t *ten_addon_protocol_find(const char *protocol) {
 static ten_addon_create_protocol_info_t *ten_addon_create_protocol_info_create(
     const char *uri, TEN_PROTOCOL_ROLE role,
     ten_env_addon_on_create_protocol_async_cb_t cb, void *user_data) {
-  TEN_ASSERT(uri && role > TEN_PROTOCOL_ROLE_INVALID, "Should not happen.");
+  TEN_ASSERT(role > TEN_PROTOCOL_ROLE_INVALID, "Should not happen.");
 
   ten_addon_create_protocol_info_t *info =
       (ten_addon_create_protocol_info_t *)TEN_MALLOC(
           sizeof(ten_addon_create_protocol_info_t));
   TEN_ASSERT(info, "Failed to allocate memory.");
 
-  ten_string_init_formatted(&info->uri, "%s", uri);
+  if (!uri || strlen(uri) == 0) {
+    ten_string_init(&info->uri);
+  } else {
+    ten_string_init_formatted(&info->uri, "%s", uri);
+  }
+
   info->role = role;
   info->cb = cb;
   info->user_data = user_data;
@@ -150,8 +155,11 @@ static void proxy_on_addon_protocol_created(ten_env_t *ten_env, void *instance,
   if (protocol) {
     ten_protocol_determine_default_property_value(protocol);
 
-    ten_string_set_formatted(&protocol->uri, "%s",
-                             ten_string_get_raw_str(&info->uri));
+    if (!ten_string_is_empty(&info->uri)) {
+      ten_string_set_formatted(&protocol->uri, "%s",
+                               ten_string_get_raw_str(&info->uri));
+    }
+
     protocol->role = info->role;
   }
 
@@ -162,7 +170,7 @@ static void proxy_on_addon_protocol_created(ten_env_t *ten_env, void *instance,
   ten_addon_create_protocol_info_destroy(info);
 }
 
-bool ten_addon_create_protocol_async(
+bool ten_addon_create_protocol_with_uri(
     ten_env_t *ten_env, const char *uri, TEN_PROTOCOL_ROLE role,
     ten_env_addon_on_create_protocol_async_cb_t cb, void *user_data,
     ten_error_t *err) {
@@ -222,3 +230,47 @@ bool ten_addon_create_protocol_async(
 
   return true;
 }
+
+bool ten_addon_create_protocol(ten_env_t *ten_env, const char *addon_name,
+                               const char *instance_name,
+                               TEN_PROTOCOL_ROLE role,
+                               ten_env_addon_on_create_protocol_async_cb_t cb,
+                               void *user_data, ten_error_t *err) {
+  TEN_ASSERT(addon_name && instance_name, "Should not happen.");
+  TEN_ASSERT(role > TEN_PROTOCOL_ROLE_INVALID, "Should not happen.");
+  TEN_ASSERT(ten_env && ten_env_check_integrity(ten_env, true),
+             "Should not happen.");
+
+  TEN_ENV_ATTACH_TO attach_to = ten_env_get_attach_to(ten_env);
+  if (attach_to != TEN_ENV_ATTACH_TO_APP &&
+      attach_to != TEN_ENV_ATTACH_TO_ENGINE) {
+    TEN_LOGE("Invalid ten_env attach_to: %d", attach_to);
+    if (err) {
+      ten_error_set(err, TEN_ERRNO_INVALID_ARGUMENT, "Invalid ten_env.");
+    }
+    return false;
+  }
+
+  TEN_LOGD("Loading protocol addon: %s", addon_name);
+
+  ten_addon_create_protocol_info_t *info =
+      ten_addon_create_protocol_info_create(NULL, role, cb, user_data);
+  TEN_ASSERT(info, "Failed to allocate memory.");
+
+  bool rc = ten_addon_create_instance_async(
+      ten_env, addon_name, instance_name, TEN_ADDON_TYPE_PROTOCOL,
+      proxy_on_addon_protocol_created, info);
+
+  if (!rc) {
+    TEN_LOGE("Failed to create protocol for %s", addon_name);
+    ten_addon_create_protocol_info_destroy(info);
+
+    if (err) {
+      ten_error_set(err, TEN_ERRNO_GENERIC,
+                    "Failed to create protocol for addon: %s.", addon_name);
+    }
+    return false;
+  }
+
+  return true;
+}
diff --git a/core/src/ten_runtime/app/ten_env/on_xxx.c b/core/src/ten_runtime/app/ten_env/on_xxx.c
index d08e7545e..558216492 100644
--- a/core/src/ten_runtime/app/ten_env/on_xxx.c
+++ b/core/src/ten_runtime/app/ten_env/on_xxx.c
@@ -161,7 +161,7 @@ void ten_app_on_configure_done(ten_env_t *ten_env) {
 
   if (!ten_string_is_equal_c_str(&self->uri, TEN_STR_LOCALHOST)) {
     // Create the app listening endpoint protocol if specifying one.
-    rc = ten_addon_create_protocol_async(
+    rc = ten_addon_create_protocol_with_uri(
         self->ten_env, ten_string_get_raw_str(&self->uri),
         TEN_PROTOCOL_ROLE_LISTEN, ten_app_on_endpoint_protocol_created, NULL,
         &err);
diff --git a/core/src/ten_runtime/binding/go/native/ten_env/ten_env_addon_create_extension.c b/core/src/ten_runtime/binding/go/native/ten_env/ten_env_addon_create_extension.c
index 5ca12f9ee..7b001ff18 100644
--- a/core/src/ten_runtime/binding/go/native/ten_env/ten_env_addon_create_extension.c
+++ b/core/src/ten_runtime/binding/go/native/ten_env/ten_env_addon_create_extension.c
@@ -118,7 +118,7 @@ static void ten_env_proxy_notify_addon_create_extension(ten_env_t *ten_env,
   ten_error_t err;
   ten_error_init(&err);
 
-  bool rc = ten_addon_create_extension_async(
+  bool rc = ten_addon_create_extension(
       ten_env, ten_string_get_raw_str(&info->addon_name),
       ten_string_get_raw_str(&info->instance_name),
       proxy_addon_create_extension_done, info->callback_info, &err);
diff --git a/core/src/ten_runtime/binding/go/native/ten_env/ten_env_addon_destroy_extension.c b/core/src/ten_runtime/binding/go/native/ten_env/ten_env_addon_destroy_extension.c
index f7a7c248d..91bbbc19d 100644
--- a/core/src/ten_runtime/binding/go/native/ten_env/ten_env_addon_destroy_extension.c
+++ b/core/src/ten_runtime/binding/go/native/ten_env/ten_env_addon_destroy_extension.c
@@ -92,9 +92,9 @@ static void ten_env_proxy_notify_addon_destroy_extension(ten_env_t *ten_env,
   ten_error_t err;
   ten_error_init(&err);
 
-  bool rc = ten_addon_destroy_extension_async(
-      ten_env, info->c_extension, proxy_addon_destroy_extension_done, info,
-      &err);
+  bool rc = ten_addon_destroy_extension(ten_env, info->c_extension,
+                                        proxy_addon_destroy_extension_done,
+                                        info, &err);
   TEN_ASSERT(rc, "Should not happen.");
 
   ten_error_deinit(&err);
diff --git a/core/src/ten_runtime/engine/internal/remote_interface.c b/core/src/ten_runtime/engine/internal/remote_interface.c
index 086811631..9ad8d4a42 100644
--- a/core/src/ten_runtime/engine/internal/remote_interface.c
+++ b/core/src/ten_runtime/engine/internal/remote_interface.c
@@ -255,7 +255,7 @@ static bool ten_engine_create_remote_async(
       ten_engine_on_protocol_created_info_create(on_remote_created_cb, cb_data);
   TEN_ASSERT(info, "Failed to allocate memory.");
 
-  bool rc = ten_addon_create_protocol_async(
+  bool rc = ten_addon_create_protocol_with_uri(
       self->ten_env, uri, TEN_PROTOCOL_ROLE_OUT_DEFAULT,
       ten_engine_on_remote_protocol_created, info, &err);
   if (!rc) {
diff --git a/core/src/ten_runtime/extension_context/extension_context.c b/core/src/ten_runtime/extension_context/extension_context.c
index 6057fc3b7..ee4a79d00 100644
--- a/core/src/ten_runtime/extension_context/extension_context.c
+++ b/core/src/ten_runtime/extension_context/extension_context.c
@@ -401,7 +401,7 @@ static void destroy_extension_group_by_addon(
   TEN_ASSERT(ten_env && ten_env_check_integrity(ten_env, true),
              "Should not happen.");
 
-  ten_addon_extension_group_destroy(
+  ten_addon_destroy_extension_group(
       ten_env, extension_group,
       ten_extension_context_on_extension_group_destroyed, NULL);
 }
@@ -566,7 +566,7 @@ bool ten_extension_context_start_extension_group(
     // `app`.
     if (ten_string_is_equal(&extension_group_info->loc.app_uri,
                             &self->engine->app->uri)) {
-      bool res = ten_addon_extension_group_create(
+      bool res = ten_addon_create_extension_group(
           ten_env,
           ten_string_get_raw_str(
               &extension_group_info->extension_group_addon_name),
diff --git a/core/src/ten_runtime/extension_group/builtin/builtin_extension_group.c b/core/src/ten_runtime/extension_group/builtin/builtin_extension_group.c
index 1133bc4d2..1b39c0e39 100644
--- a/core/src/ten_runtime/extension_group/builtin/builtin_extension_group.c
+++ b/core/src/ten_runtime/extension_group/builtin/builtin_extension_group.c
@@ -121,7 +121,7 @@ static void ten_builtin_extension_group_on_create_extensions(
     ten_string_t *extension_addon_name = &extension_name_info->addon_name;
     ten_string_t *extension_instance_name = &extension_name_info->instance_name;
 
-    bool res = ten_addon_create_extension_async(
+    bool res = ten_addon_create_extension(
         ten_env, ten_string_get_raw_str(extension_addon_name),
         ten_string_get_raw_str(extension_instance_name),
         (ten_env_addon_on_create_instance_async_cb_t)
@@ -156,8 +156,8 @@ static void ten_builtin_extension_group_on_destroy_extensions(
     TEN_ASSERT(extension && ten_extension_check_integrity(extension, true),
                "Invalid argument.");
 
-    ten_addon_destroy_extension_async(
-        ten_env, extension, on_addon_destroy_instance_done, NULL, NULL);
+    ten_addon_destroy_extension(ten_env, extension,
+                                on_addon_destroy_instance_done, NULL, NULL);
   }
 }
 
diff --git a/core/src/ten_runtime/protocol/asynced/protocol_asynced.c b/core/src/ten_runtime/protocol/asynced/protocol_asynced.c
index e010acc24..9f6f534d4 100644
--- a/core/src/ten_runtime/protocol/asynced/protocol_asynced.c
+++ b/core/src/ten_runtime/protocol/asynced/protocol_asynced.c
@@ -398,7 +398,7 @@ void ten_protocol_asynced_on_connected_async(ten_protocol_asynced_t *self,
 }
 
 static void ten_app_thread_on_client_protocol_created(ten_env_t *ten_env,
-                                                      void *instance,
+                                                      ten_protocol_t *instance,
                                                       void *cb_data) {
   TEN_ASSERT(ten_env && ten_env_check_integrity(ten_env, true),
              "Should not happen.");
@@ -415,7 +415,7 @@ static void ten_app_thread_on_client_protocol_created(ten_env_t *ten_env,
                  ten_protocol_check_integrity(&listening_protocol->base, true),
              "Invalid argument.");
 
-  ten_protocol_asynced_t *protocol = instance;
+  ten_protocol_asynced_t *protocol = (ten_protocol_asynced_t *)instance;
   if (!protocol) {
     TEN_LOGE("Failed to create the protocol instance.");
     info->on_created(NULL, info);
@@ -427,13 +427,6 @@ static void ten_app_thread_on_client_protocol_created(ten_env_t *ten_env,
   // object) might need to be migrated, so set the value to 'INIT' as the
   // default value is 'DONE'. Refer to 'ten_protocol_asynced_init()'.
   protocol->migration_state = TEN_CONNECTION_MIGRATION_STATE_INIT;
-
-  // We can _not_ know whether the protocol role is
-  // 'TEN_PROTOCOL_ROLE_IN_INTERNAL' or 'TEN_PROTOCOL_ROLE_IN_EXTERNAL' until
-  // the message received from the protocol is processed. Refer to
-  // 'ten_connection_on_msgs()' and
-  // 'ten_connection_handle_command_from_external_client()'.
-  protocol->base.role = TEN_PROTOCOL_ROLE_IN_DEFAULT;
   protocol->base.on_accepted = listening_protocol->base.on_accepted;
 
   ten_protocol_attach_to_app_and_thread(&protocol->base, app);
@@ -473,11 +466,22 @@ static void ten_protocol_asynced_on_client_accepted(void *self, void *info_) {
     ten_app_t *app = listening_base_protocol->attached_target.app;
     TEN_ASSERT(app && ten_app_check_integrity(app, true), "Should not happen.");
 
-    bool rc = ten_addon_create_instance_async(
+    ten_error_t err;
+    ten_error_init(&err);
+
+    // We can _not_ know whether the protocol role is
+    // 'TEN_PROTOCOL_ROLE_IN_INTERNAL' or 'TEN_PROTOCOL_ROLE_IN_EXTERNAL'
+    // until the message received from the protocol is processed. Refer to
+    // 'ten_connection_on_msgs()' and
+    // 'ten_connection_handle_command_from_external_client()'.
+    bool rc = ten_addon_create_protocol(
         app->ten_env, ten_string_get_raw_str(&addon_host->name),
-        ten_string_get_raw_str(&addon_host->name), TEN_ADDON_TYPE_PROTOCOL,
-        ten_app_thread_on_client_protocol_created, info);
-    TEN_ASSERT(rc, "Should not happen.");
+        ten_string_get_raw_str(&addon_host->name), TEN_PROTOCOL_ROLE_IN_DEFAULT,
+        ten_app_thread_on_client_protocol_created, info, NULL);
+    TEN_ASSERT(rc, "Failed to create protocol, err: %s",
+               ten_error_errmsg(&err));
+
+    ten_error_deinit(&err);
   }
 
   // The task is completed, so delete a reference to the 'protocol' to reflect
diff --git a/core/src/ten_runtime/protocol/integrated/protocol_integrated.c b/core/src/ten_runtime/protocol/integrated/protocol_integrated.c
index e7c23ac35..4d18ea844 100644
--- a/core/src/ten_runtime/protocol/integrated/protocol_integrated.c
+++ b/core/src/ten_runtime/protocol/integrated/protocol_integrated.c
@@ -30,6 +30,7 @@
 #include "ten_utils/io/runloop.h"
 #include "ten_utils/io/stream.h"
 #include "ten_utils/lib/alloc.h"
+#include "ten_utils/lib/error.h"
 #include "ten_utils/lib/mutex.h"
 #include "ten_utils/lib/ref.h"
 #include "ten_utils/lib/smart_ptr.h"
@@ -272,12 +273,12 @@ static void ten_protocol_integrated_set_stream(ten_protocol_integrated_t *self,
 }
 
 static void ten_app_thread_on_client_protocol_created(ten_env_t *ten_env,
-                                                      void *instance,
+                                                      ten_protocol_t *instance,
                                                       void *cb_data) {
   TEN_ASSERT(ten_env && ten_env_check_integrity(ten_env, true),
              "Should not happen.");
 
-  ten_protocol_integrated_t *protocol = instance;
+  ten_protocol_integrated_t *protocol = (ten_protocol_integrated_t *)instance;
   TEN_ASSERT(protocol && ten_protocol_check_integrity(&protocol->base, true),
              "Should not happen.");
 
@@ -304,13 +305,6 @@ static void ten_app_thread_on_client_protocol_created(ten_env_t *ten_env,
   new_communication_base_protocol->on_connected =
       listening_base_protocol->on_connected;
 
-  // We can _not_ know whether the protocol role is
-  // 'TEN_PROTOCOL_ROLE_IN_INTERNAL' or 'TEN_PROTOCOL_ROLE_IN_EXTERNAL' until
-  // the message received from the protocol is processed. Refer to
-  // 'ten_connection_on_msgs()' and
-  // 'ten_connection_handle_command_from_external_client()'.
-  new_communication_base_protocol->role = TEN_PROTOCOL_ROLE_IN_DEFAULT;
-
   // Attach the newly created protocol to app first.
   ten_protocol_attach_to_app(new_communication_base_protocol,
                              listening_base_protocol->attached_target.app);
@@ -344,13 +338,23 @@ static void ten_protocol_integrated_on_client_accepted(
   ten_app_t *app = listening_base_protocol->attached_target.app;
   TEN_ASSERT(app && ten_app_check_integrity(app, true), "Should not happen.");
 
-  bool rc = ten_addon_create_instance_async(
+  ten_error_t err;
+  ten_error_init(&err);
+
+  // We can _not_ know whether the protocol role is
+  // 'TEN_PROTOCOL_ROLE_IN_INTERNAL' or 'TEN_PROTOCOL_ROLE_IN_EXTERNAL' until
+  // the message received from the protocol is processed. Refer to
+  // 'ten_connection_on_msgs()' and
+  // 'ten_connection_handle_command_from_external_client()'.
+  bool rc = ten_addon_create_protocol(
       app->ten_env,
       ten_string_get_raw_str(&listening_base_protocol->addon_host->name),
       ten_string_get_raw_str(&listening_base_protocol->addon_host->name),
-      TEN_ADDON_TYPE_PROTOCOL, ten_app_thread_on_client_protocol_created,
-      stream);
-  TEN_ASSERT(rc, "Should not happen.");
+      TEN_PROTOCOL_ROLE_IN_DEFAULT, ten_app_thread_on_client_protocol_created,
+      stream, &err);
+  TEN_ASSERT(rc, "Failed to create protocol, err: %s", ten_error_errmsg(&err));
+
+  ten_error_deinit(&err);
 }
 
 static void ten_protocol_integrated_listen(ten_protocol_integrated_t *self,