diff --git a/lib/callbacks.h b/lib/callbacks.h
new file mode 100644
index 00000000..63dc7f50
--- /dev/null
+++ b/lib/callbacks.h
@@ -0,0 +1,31 @@
+/*
+Copyright (c) 2021 Roger Light <roger@atchoo.org>
+
+All rights reserved. This program and the accompanying materials
+are made available under the terms of the Eclipse Public License 2.0
+and Eclipse Distribution License v1.0 which accompany this distribution.
+ 
+The Eclipse Public License is available at
+   https://www.eclipse.org/legal/epl-2.0/
+and the Eclipse Distribution License is available at
+  http://www.eclipse.org/org/documents/edl-v10.php.
+ 
+SPDX-License-Identifier: EPL-2.0 OR EDL-1.0
+
+Contributors:
+   Roger Light - initial implementation and documentation.
+*/
+#ifndef CALLBACKS_H
+#define CALLBACKS_H
+
+#include "mosquitto.h"
+
+void callback__on_pre_connect(struct mosquitto *mosq);
+void callback__on_connect(struct mosquitto *mosq, uint8_t reason_code, uint8_t connect_flags, const mosquitto_property *properties);
+void callback__on_publish(struct mosquitto *mosq, int mid, int reason_code, const mosquitto_property *properties);
+void callback__on_message(struct mosquitto *mosq, const struct mosquitto_message *message, const mosquitto_property *properties);
+void callback__on_subscribe(struct mosquitto *mosq, int mid, int qos_count, const int *granted_qos, const mosquitto_property *props);
+void callback__on_unsubscribe(struct mosquitto *mosq, int mid, const mosquitto_property *props);
+void callback__on_disconnect(struct mosquitto *mosq, int rc, const mosquitto_property *props);
+
+#endif