diff --git a/cdb_assist.c b/cdb_assist.c
index 0ad1b1b..549afbd 100644
--- a/cdb_assist.c
+++ b/cdb_assist.c
@@ -344,7 +344,6 @@ unsigned int cdb_vref(struct cdb_assist *cdb)
 void cdb_assist_print_status(struct device *dev)
 {
 	struct cdb_assist *cdb = dev->cdb;
-	struct msg hdr;
 	char buf[128];
 	int n;
 
@@ -358,10 +357,7 @@ void cdb_assist_print_status(struct device *dev)
 			 cdb->btn[2] ? " btn3" : "",
 			 cdb->vref);
 
-	hdr.type = MSG_STATUS_UPDATE;
-	hdr.len = n;
-	write(STDOUT_FILENO, &hdr, sizeof(hdr));
-	write(STDOUT_FILENO, buf, n);
+	cdba_send_buf(MSG_STATUS_UPDATE, n, buf);
 }
 
 void cdb_set_voltage(struct cdb_assist *cdb, unsigned mV)
diff --git a/cdba-server.c b/cdba-server.c
index ceec6a0..5bd7a25 100644
--- a/cdba-server.c
+++ b/cdba-server.c
@@ -82,16 +82,10 @@ int tty_open(const char *tty, struct termios *old)
 static void fastboot_opened(struct fastboot *fb, void *data)
 {
 	const uint8_t one = 1;
-	struct msg *msg;
 
 	warnx("fastboot connection opened");
 
-	msg = alloca(sizeof(*msg) + 1);
-	msg->type = MSG_FASTBOOT_PRESENT;
-	msg->len = 1;
-	memcpy(msg->data, &one, 1);
-
-	write(STDOUT_FILENO, msg, sizeof(*msg) + 1);
+	cdba_send_buf(MSG_FASTBOOT_PRESENT, 1, &one);
 }
 
 static void fastboot_info(struct fastboot *fb, const void *buf, size_t len)
@@ -102,14 +96,8 @@ static void fastboot_info(struct fastboot *fb, const void *buf, size_t len)
 static void fastboot_disconnect(void *data)
 {
 	const uint8_t zero = 0;
-	struct msg *msg;
 
-	msg = alloca(sizeof(*msg) + 1);
-	msg->type = MSG_FASTBOOT_PRESENT;
-	msg->len = 1;
-	memcpy(msg->data, &zero, 1);
-
-	write(STDOUT_FILENO, msg, sizeof(*msg) + 1);
+	cdba_send_buf(MSG_FASTBOOT_PRESENT, 1, &zero);
 }
 
 static struct fastboot_ops fastboot_ops = {
@@ -120,15 +108,13 @@ static struct fastboot_ops fastboot_ops = {
 
 static void msg_select_board(const void *param)
 {
-	struct msg reply = { MSG_SELECT_BOARD, 0 };
-
 	selected_device = device_open(param, username, &fastboot_ops);
 	if (!selected_device) {
 		fprintf(stderr, "failed to open %s\n", (const char *)param);
 		quit_invoked = true;
 	}
 
-	write(STDOUT_FILENO, &reply, sizeof(reply));
+	cdba_send(MSG_SELECT_BOARD);
 }
 
 static void *fastboot_payload;
@@ -136,7 +122,6 @@ static size_t fastboot_size;
 
 static void msg_fastboot_download(const void *data, size_t len)
 {
-	struct msg reply = { MSG_FASTBOOT_DOWNLOAD, };
 	size_t new_size = fastboot_size + len;
 	char *newp;
 
@@ -152,18 +137,23 @@ static void msg_fastboot_download(const void *data, size_t len)
 	if (!len) {
 		device_boot(selected_device, fastboot_payload, fastboot_size);
 
-		write(STDOUT_FILENO, &reply, sizeof(reply));
+		cdba_send(MSG_FASTBOOT_DOWNLOAD);
 		free(fastboot_payload);
 		fastboot_payload = NULL;
 		fastboot_size = 0;
 	}
 }
 
-static void invoke_reply(int reply)
+void cdba_send_buf(int type, size_t len, const void *buf)
 {
-	struct msg msg = { reply, };
+	struct msg msg = {
+		.type = type,
+		.len = len
+	};
 
 	write(STDOUT_FILENO, &msg, sizeof(msg));
+	if (len)
+		write(STDOUT_FILENO, buf, len);
 }
 
 static int handle_stdin(int fd, void *buf)
@@ -206,12 +196,12 @@ static int handle_stdin(int fd, void *buf)
 		case MSG_POWER_ON:
 			device_power(selected_device, true);
 
-			invoke_reply(MSG_POWER_ON);
+			cdba_send(MSG_POWER_ON);
 			break;
 		case MSG_POWER_OFF:
 			device_power(selected_device, false);
 
-			invoke_reply(MSG_POWER_OFF);
+			cdba_send(MSG_POWER_OFF);
 			break;
 		case MSG_FASTBOOT_DOWNLOAD:
 			msg_fastboot_download(msg->data, msg->len);
diff --git a/cdba-server.h b/cdba-server.h
index 5c870d7..0dd6f26 100644
--- a/cdba-server.h
+++ b/cdba-server.h
@@ -14,4 +14,7 @@ int watch_run(void);
 
 int tty_open(const char *tty, struct termios *old);
 
+void cdba_send_buf(int type, size_t len, const void *buf);
+#define cdba_send(type) cdba_send_buf(type, 0, NULL)
+
 #endif
diff --git a/conmux.c b/conmux.c
index 3d71e62..4b0b670 100644
--- a/conmux.c
+++ b/conmux.c
@@ -207,7 +207,6 @@ out:
 
 static int conmux_data(int fd, void *data)
 {
-	struct msg hdr;
 	char buf[128];
 	ssize_t n;
 
@@ -219,10 +218,7 @@ static int conmux_data(int fd, void *data)
 		fprintf(stderr, "Received EOF from conmux\n");
 		watch_quit();
 	} else {
-		hdr.type = MSG_CONSOLE;
-		hdr.len = n;
-		write(STDOUT_FILENO, &hdr, sizeof(hdr));
-		write(STDOUT_FILENO, buf, n);
+		cdba_send_buf(MSG_CONSOLE, n, buf);
 	}
 
 	return 0;
diff --git a/console.c b/console.c
index 2cab31a..0a21523 100644
--- a/console.c
+++ b/console.c
@@ -39,7 +39,6 @@
 
 static int console_data(int fd, void *data)
 {
-	struct msg hdr;
 	char buf[128];
 	ssize_t n;
 
@@ -47,10 +46,7 @@ static int console_data(int fd, void *data)
 	if (n < 0)
 		return n;
 
-	hdr.type = MSG_CONSOLE;
-	hdr.len = n;
-	write(STDOUT_FILENO, &hdr, sizeof(hdr));
-	write(STDOUT_FILENO, buf, n);
+	cdba_send_buf(MSG_CONSOLE, n, buf);
 
 	return 0;
 }
diff --git a/device.c b/device.c
index 1b0e3b9..826b038 100644
--- a/device.c
+++ b/device.c
@@ -301,7 +301,6 @@ void device_send_break(struct device *device)
 void device_list_devices(const char *username)
 {
 	struct device *device;
-	struct msg hdr;
 	size_t len;
 	char buf[80];
 
@@ -314,22 +313,16 @@ void device_list_devices(const char *username)
 		else
 			len = snprintf(buf, sizeof(buf), "%s", device->board);
 
-		hdr.type = MSG_LIST_DEVICES;
-		hdr.len = len;
-		write(STDOUT_FILENO, &hdr, sizeof(hdr));
-		write(STDOUT_FILENO, buf, len);
+		cdba_send_buf(MSG_LIST_DEVICES, len, buf);
 	}
 
-	hdr.type = MSG_LIST_DEVICES;
-	hdr.len = 0;
-	write(STDOUT_FILENO, &hdr, sizeof(hdr));
+	cdba_send_buf(MSG_LIST_DEVICES, 0, NULL);
 }
 
 void device_info(const char *username, const void *data, size_t dlen)
 {
+	char *description = NULL;
 	struct device *device;
-	struct msg hdr;
-	char *description;
 	size_t len = 0;
 
 	list_for_each_entry(device, &devices, node) {
@@ -346,11 +339,7 @@ void device_info(const char *username, const void *data, size_t dlen)
 		}
 	}
 
-	hdr.type = MSG_BOARD_INFO;
-	hdr.len = len;
-	write(STDOUT_FILENO, &hdr, sizeof(hdr));
-	if (len)
-		write(STDOUT_FILENO, description, len);
+	cdba_send_buf(MSG_BOARD_INFO, len, description);
 }
 
 void device_close(struct device *dev)