diff --git a/tools/helper/handler.h b/tools/helper/handler.h
new file mode 100644
index 0000000..56d4211
--- /dev/null
+++ b/tools/helper/handler.h
@@ -0,0 +1,181 @@
+#pragma once
+#include "common.h"
+#include <rawrtc.h>
+#include <rawrtcc.h>
+#include <rawrtcdc.h>
+#include <re.h>
+
+/*
+ * Print the ICE gatherer's state.
+ */
+void default_ice_gatherer_state_change_handler(
+    enum rawrtc_ice_gatherer_state const state,  // read-only
+    void* const arg);
+
+/*
+ * Print the ICE gatherer's error event.
+ */
+void default_ice_gatherer_error_handler(
+    struct rawrtc_ice_candidate* const host_candidate,  // read-only, nullable
+    char const* const url,  // read-only
+    uint16_t const error_code,  // read-only
+    char const* const error_text,  // read-only
+    void* const arg  // will be casted to `struct client*`
+);
+
+/*
+ * Print the newly gatherered local candidate.
+ * Will print local parameters on stdout in case the client is not
+ * used in loopback mode.
+ */
+void default_ice_gatherer_local_candidate_handler(
+    struct rawrtc_ice_candidate* const candidate,
+    char const* const url,  // read-only
+    void* const arg  // will be casted to `struct client*`
+);
+
+/*
+ * Print the ICE transport's state.
+ */
+void default_ice_transport_state_change_handler(
+    enum rawrtc_ice_transport_state const state,
+    void* const arg  // will be casted to `struct client*`
+);
+
+/*
+ * Print the ICE candidate pair change event.
+ */
+void default_ice_transport_candidate_pair_change_handler(
+    struct rawrtc_ice_candidate* const local,  // read-only
+    struct rawrtc_ice_candidate* const remote,  // read-only
+    void* const arg  // will be casted to `struct client*`
+);
+
+/*
+ * Print the DTLS transport's state.
+ */
+void default_dtls_transport_state_change_handler(
+    enum rawrtc_dtls_transport_state const state,  // read-only
+    void* const arg  // will be casted to `struct client*`
+);
+
+/*
+ * Print the DTLS transport's error event.
+ */
+void default_dtls_transport_error_handler(
+    // TODO: error.message (probably from OpenSSL)
+    void* const arg  // will be casted to `struct client*`
+);
+
+#if RAWRTC_HAVE_SCTP_REDIRECT_TRANSPORT
+/*
+ * Print the SCTP redirect transport's state.
+ */
+void default_sctp_redirect_transport_state_change_handler(
+    enum rawrtc_sctp_redirect_transport_state const state,
+    void* const arg  // will be casted to `struct client*`
+);
+#endif
+
+/*
+ * Print the SCTP transport's state.
+ */
+void default_sctp_transport_state_change_handler(
+    enum rawrtc_sctp_transport_state const state,
+    void* const arg  // will be casted to `struct client*`
+);
+
+/*
+ * Print the newly created data channel's parameter.
+ */
+void default_data_channel_handler(
+    struct rawrtc_data_channel* const data_channel,  // read-only, MUST be referenced when used
+    void* const arg  // will be casted to `struct data_channel_helper*`
+);
+
+/*
+ * Print the data channel open event.
+ */
+void default_data_channel_open_handler(
+    void* const arg  // will be casted to `struct data_channel_helper*`
+);
+
+/*
+ * Print the data channel buffered amount low event.
+ */
+void default_data_channel_buffered_amount_low_handler(
+    void* const arg  // will be casted to `struct data_channel_helper*`
+);
+
+/*
+ * Print the data channel error event.
+ */
+void default_data_channel_error_handler(
+    void* const arg  // will be casted to `struct data_channel_helper*`
+);
+
+/*
+ * Print the data channel close event.
+ */
+void default_data_channel_close_handler(
+    void* const arg  // will be casted to `struct data_channel_helper*`
+);
+
+/*
+ * Print the data channel's received message's size.
+ */
+void default_data_channel_message_handler(
+    struct mbuf* const buffer,
+    enum rawrtc_data_channel_message_flag const flags,
+    void* const arg  // will be casted to `struct data_channel_helper*`
+);
+
+/*
+ * Print negotiation needed (duh!)
+ */
+void default_negotiation_needed_handler(void* const arg);
+
+/*
+ * Print the peer connection's state.
+ */
+void default_peer_connection_state_change_handler(
+    enum rawrtc_peer_connection_state const state,  // read-only
+    void* const arg  // will be casted to `struct client*`
+);
+
+/*
+ * Print the newly gathered local candidate (peer connection variant).
+ */
+void default_peer_connection_local_candidate_handler(
+    struct rawrtc_peer_connection_ice_candidate* const candidate,
+    char const* const url,  // read-only
+    void* const arg);
+
+/*
+ * Print the peer connections local candidate error event.
+ */
+void default_peer_connection_local_candidate_error_handler(
+    struct rawrtc_peer_connection_ice_candidate* const candidate,  // read-only, nullable
+    char const* const url,  // read-only
+    uint16_t const error_code,  // read-only
+    char const* const error_text,  // read-only
+    void* const arg  // will be casted to `struct client*`
+);
+
+/*
+ * Print the signaling state.
+ */
+void default_signaling_state_change_handler(
+    enum rawrtc_signaling_state const state,  // read-only
+    void* const arg);
+
+/*
+ * Stop the main loop.
+ */
+void default_signal_handler(int sig);
+
+/*
+ * FD-listener that stops the main loop in case the input buffer is
+ * empty.
+ */
+void stop_on_return_handler(int flags, void* arg);