diff --git a/tools/helper/common.h b/tools/helper/common.h
new file mode 100644
index 0000000..e2a34ad
--- /dev/null
+++ b/tools/helper/common.h
@@ -0,0 +1,95 @@
+#pragma once
+#include <rawrtc.h>
+#include <rawrtcc.h>
+#include <rawrtcdc.h>
+#include <re.h>
+
+enum {
+    PARAMETERS_MAX_LENGTH = 8192,
+};
+
+/*
+ * SCTP parameters that need to be negotiated.
+ */
+struct sctp_parameters {
+    struct rawrtc_sctp_capabilities* capabilities;
+    uint16_t port;
+};
+
+/*
+ * Client structure. Can be extended.
+ */
+struct client {
+    char* name;
+    char** ice_candidate_types;
+    size_t n_ice_candidate_types;
+};
+
+/*
+ * Data channel helper structure. Can be extended.
+ */
+struct data_channel_helper {
+    struct le le;
+    struct rawrtc_data_channel* channel;
+    char* label;
+    struct client* client;
+    void* arg;
+};
+
+/*
+ * Ignore success code list.
+ */
+extern enum rawrtc_code const ignore_success[];
+extern size_t const ignore_success_length;
+
+/*
+ * Helper macros for exiting with error messages.
+ */
+#define EOE(code) exit_on_error(code, ignore_success, ignore_success_length, __FILE__, __LINE__)
+#define EOEIGN(code, ignore) exit_on_error(code, ignore, ARRAY_SIZE(ignore), __FILE__, __LINE__)
+#define EOR(code) exit_on_posix_error(code, __FILE__, __LINE__)
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) || (__GNUC__ >= 3)
+#    define EWE(...) exit_with_error(__FILE__, __LINE__, __VA_ARGS__)
+#elif defined(__GNUC__)
+#    define EWE(args...) exit_with_error(__FILE__, __LINE__, args)
+#endif
+
+/*
+ * Function to be called before exiting.
+ */
+void before_exit(void);
+
+/*
+ * Exit on error code.
+ */
+void exit_on_error(
+    enum rawrtc_code const code,
+    enum rawrtc_code const ignore[],
+    size_t const n_ignore,
+    char const* const file,
+    uint32_t const line);
+
+/*
+ * Exit on POSIX error code.
+ */
+void exit_on_posix_error(int code, char const* const file, uint32_t line);
+
+/*
+ * Exit with a custom error message.
+ */
+void exit_with_error(char const* const file, uint32_t line, char const* const formatter, ...);
+
+/*
+ * Check if the ICE candidate type is enabled.
+ */
+bool ice_candidate_type_enabled(
+    struct client* const client, enum rawrtc_ice_candidate_type const type);
+
+/*
+ * Print ICE candidate information.
+ */
+void print_ice_candidate(
+    struct rawrtc_ice_candidate* const candidate,
+    char const* const url,  // read-only
+    struct rawrtc_peer_connection_ice_candidate* const pc_candidate,  // nullable
+    struct client* const client);