static void build_udp_url(char *buf, int buf_size, const char *hostname, int port, int local_port, int ttl) { snprintf(buf, buf_size, "udp://%s:%d", hostname, port); if (local_port >= 0) url_add_option(buf, buf_size, "localport=%d", local_port); if (ttl >= 0) url_add_option(buf, buf_size, "ttl=%d", ttl); }