diff --git a/include/libdivecomputer/common.h b/include/libdivecomputer/common.h
index 293de3b..c6c093a 100644
--- a/include/libdivecomputer/common.h
+++ b/include/libdivecomputer/common.h
@@ -41,6 +41,15 @@ typedef enum dc_status_t {
 	DC_STATUS_CANCELLED = -10
 } dc_status_t;
 
+typedef enum dc_transport_t {
+	DC_TRANSPORT_NONE,
+	DC_TRANSPORT_SERIAL,
+	DC_TRANSPORT_USB,
+	DC_TRANSPORT_USBHID,
+	DC_TRANSPORT_IRDA,
+	DC_TRANSPORT_BLUETOOTH
+} dc_transport_t;
+
 typedef enum dc_family_t {
 	DC_FAMILY_NULL = 0,
 	/* Suunto */
diff --git a/include/libdivecomputer/descriptor.h b/include/libdivecomputer/descriptor.h
index a78b600..12d9bab 100644
--- a/include/libdivecomputer/descriptor.h
+++ b/include/libdivecomputer/descriptor.h
@@ -29,15 +29,6 @@
 extern "C" {
 #endif /* __cplusplus */
 
-typedef enum dc_transport_t {
-	DC_TRANSPORT_NONE,
-	DC_TRANSPORT_SERIAL,
-	DC_TRANSPORT_USB,
-	DC_TRANSPORT_USBHID,
-	DC_TRANSPORT_IRDA,
-	DC_TRANSPORT_BLUETOOTH
-} dc_transport_t;
-
 typedef struct dc_descriptor_t dc_descriptor_t;
 
 dc_status_t
diff --git a/include/libdivecomputer/iostream.h b/include/libdivecomputer/iostream.h
index 832680d..e2cb439 100644
--- a/include/libdivecomputer/iostream.h
+++ b/include/libdivecomputer/iostream.h
@@ -82,6 +82,15 @@ typedef enum dc_line_t {
 	DC_LINE_RNG = 0x08, /**< Ring indicator */
 } dc_line_t;
 
+/**
+ * Get the transport type.
+ *
+ * @param[in]  iostream  A valid I/O stream.
+ * @returns The transport type of the I/O stream.
+ */
+dc_transport_t
+dc_iostream_get_transport (dc_iostream_t *iostream);
+
 /**
  * Set the read timeout.
  *
diff --git a/src/bluetooth.c b/src/bluetooth.c
index 5a37a5b..702782d 100644
--- a/src/bluetooth.c
+++ b/src/bluetooth.c
@@ -504,7 +504,7 @@ dc_bluetooth_open (dc_iostream_t **out, dc_context_t *context, dc_bluetooth_addr
 	INFO (context, "Open: address=" DC_ADDRESS_FORMAT ", port=%u", address, port);
 
 	// Allocate memory.
-	device = (dc_socket_t *) dc_iostream_allocate (context, &dc_bluetooth_vtable);
+	device = (dc_socket_t *) dc_iostream_allocate (context, &dc_bluetooth_vtable, DC_TRANSPORT_BLUETOOTH);
 	if (device == NULL) {
 		SYSERROR (context, S_ENOMEM);
 		return DC_STATUS_NOMEMORY;
diff --git a/src/custom.c b/src/custom.c
index 519a39e..68aa881 100644
--- a/src/custom.c
+++ b/src/custom.c
@@ -69,17 +69,17 @@ static const dc_iostream_vtable_t dc_custom_vtable = {
 };
 
 dc_status_t
-dc_custom_open (dc_iostream_t **out, dc_context_t *context, const dc_custom_cbs_t *callbacks, void *userdata)
+dc_custom_open (dc_iostream_t **out, dc_context_t *context, dc_transport_t transport, const dc_custom_cbs_t *callbacks, void *userdata)
 {
 	dc_custom_t *custom = NULL;
 
 	if (out == NULL || callbacks == NULL)
 		return DC_STATUS_INVALIDARGS;
 
-	INFO (context, "Open: custom");
+	INFO (context, "Open: transport=%u", transport);
 
 	// Allocate memory.
-	custom = (dc_custom_t *) dc_iostream_allocate (context, &dc_custom_vtable);
+	custom = (dc_custom_t *) dc_iostream_allocate (context, &dc_custom_vtable, transport);
 	if (custom == NULL) {
 		ERROR (context, "Failed to allocate memory.");
 		return DC_STATUS_NOMEMORY;
diff --git a/src/custom.h b/src/custom.h
index f1ab5da..9618dce 100644
--- a/src/custom.h
+++ b/src/custom.h
@@ -58,7 +58,7 @@ typedef struct dc_custom_cbs_t {
  * on failure.
  */
 dc_status_t
-dc_custom_open (dc_iostream_t **iostream, dc_context_t *context, const dc_custom_cbs_t *callbacks, void *userdata);
+dc_custom_open (dc_iostream_t **iostream, dc_context_t *context, dc_transport_t transport, const dc_custom_cbs_t *callbacks, void *userdata);
 
 #ifdef __cplusplus
 }
diff --git a/src/iostream-private.h b/src/iostream-private.h
index b9bd4f1..f9c0883 100644
--- a/src/iostream-private.h
+++ b/src/iostream-private.h
@@ -35,6 +35,7 @@ typedef struct dc_iostream_vtable_t dc_iostream_vtable_t;
 struct dc_iostream_t {
 	const dc_iostream_vtable_t *vtable;
 	dc_context_t *context;
+	dc_transport_t transport;
 };
 
 struct dc_iostream_vtable_t {
@@ -70,7 +71,7 @@ struct dc_iostream_vtable_t {
 };
 
 dc_iostream_t *
-dc_iostream_allocate (dc_context_t *context, const dc_iostream_vtable_t *vtable);
+dc_iostream_allocate (dc_context_t *context, const dc_iostream_vtable_t *vtable, dc_transport_t transport);
 
 void
 dc_iostream_deallocate (dc_iostream_t *iostream);
diff --git a/src/iostream.c b/src/iostream.c
index c1e3017..9681d02 100644
--- a/src/iostream.c
+++ b/src/iostream.c
@@ -27,7 +27,7 @@
 #include "context-private.h"
 
 dc_iostream_t *
-dc_iostream_allocate (dc_context_t *context, const dc_iostream_vtable_t *vtable)
+dc_iostream_allocate (dc_context_t *context, const dc_iostream_vtable_t *vtable, dc_transport_t transport)
 {
 	dc_iostream_t *iostream = NULL;
 
@@ -44,6 +44,7 @@ dc_iostream_allocate (dc_context_t *context, const dc_iostream_vtable_t *vtable)
 	// Initialize the base class.
 	iostream->vtable = vtable;
 	iostream->context = context;
+	iostream->transport = transport;
 
 	return iostream;
 }
@@ -63,6 +64,15 @@ dc_iostream_isinstance (dc_iostream_t *iostream, const dc_iostream_vtable_t *vta
 	return iostream->vtable == vtable;
 }
 
+dc_transport_t
+dc_iostream_get_transport (dc_iostream_t *iostream)
+{
+	if (iostream == NULL)
+		return DC_TRANSPORT_NONE;
+
+	return iostream->transport;
+}
+
 dc_status_t
 dc_iostream_set_timeout (dc_iostream_t *iostream, int timeout)
 {
diff --git a/src/irda.c b/src/irda.c
index d1aecfb..c8adb0d 100644
--- a/src/irda.c
+++ b/src/irda.c
@@ -300,7 +300,7 @@ dc_irda_open (dc_iostream_t **out, dc_context_t *context, unsigned int address,
 	INFO (context, "Open: address=%08x, lsap=%u", address, lsap);
 
 	// Allocate memory.
-	device = (dc_socket_t *) dc_iostream_allocate (context, &dc_irda_vtable);
+	device = (dc_socket_t *) dc_iostream_allocate (context, &dc_irda_vtable, DC_TRANSPORT_IRDA);
 	if (device == NULL) {
 		SYSERROR (context, S_ENOMEM);
 		return DC_STATUS_NOMEMORY;
diff --git a/src/libdivecomputer.symbols b/src/libdivecomputer.symbols
index a0c3724..e5e55f0 100644
--- a/src/libdivecomputer.symbols
+++ b/src/libdivecomputer.symbols
@@ -33,6 +33,7 @@ dc_descriptor_get_type
 dc_descriptor_get_model
 dc_descriptor_get_transport
 
+dc_iostream_get_transport
 dc_iostream_set_timeout
 dc_iostream_set_latency
 dc_iostream_set_break
diff --git a/src/serial_posix.c b/src/serial_posix.c
index 6f2ae71..e9dbff0 100644
--- a/src/serial_posix.c
+++ b/src/serial_posix.c
@@ -271,7 +271,7 @@ dc_serial_open (dc_iostream_t **out, dc_context_t *context, const char *name)
 	INFO (context, "Open: name=%s", name);
 
 	// Allocate memory.
-	device = (dc_serial_t *) dc_iostream_allocate (context, &dc_serial_vtable);
+	device = (dc_serial_t *) dc_iostream_allocate (context, &dc_serial_vtable, DC_TRANSPORT_SERIAL);
 	if (device == NULL) {
 		SYSERROR (context, ENOMEM);
 		return DC_STATUS_NOMEMORY;
diff --git a/src/serial_win32.c b/src/serial_win32.c
index b0c6050..067bb72 100644
--- a/src/serial_win32.c
+++ b/src/serial_win32.c
@@ -276,7 +276,7 @@ dc_serial_open (dc_iostream_t **out, dc_context_t *context, const char *name)
 	}
 
 	// Allocate memory.
-	device = (dc_serial_t *) dc_iostream_allocate (context, &dc_serial_vtable);
+	device = (dc_serial_t *) dc_iostream_allocate (context, &dc_serial_vtable, DC_TRANSPORT_SERIAL);
 	if (device == NULL) {
 		SYSERROR (context, ERROR_OUTOFMEMORY);
 		return DC_STATUS_NOMEMORY;
diff --git a/src/usbhid.c b/src/usbhid.c
index 244e175..1347423 100644
--- a/src/usbhid.c
+++ b/src/usbhid.c
@@ -473,7 +473,7 @@ dc_usbhid_open (dc_iostream_t **out, dc_context_t *context, unsigned int vid, un
 	INFO (context, "Open: vid=%04x, pid=%04x", vid, pid);
 
 	// Allocate memory.
-	usbhid = (dc_usbhid_t *) dc_iostream_allocate (context, &dc_usbhid_vtable);
+	usbhid = (dc_usbhid_t *) dc_iostream_allocate (context, &dc_usbhid_vtable, DC_TRANSPORT_USBHID);
 	if (usbhid == NULL) {
 		ERROR (context, "Out of memory.");
 		return DC_STATUS_NOMEMORY;