diff --git a/raw.c b/raw.c
index d9a3468..937f473 100644
--- a/raw.c
+++ b/raw.c
@@ -290,9 +290,9 @@ static int raw_recv(struct transport *t, int fd, void *buf, int buflen,
 	return cnt;
 }
 
-static int raw_send(struct transport *t, struct fdarray *fda, int event,
-		    int peer, void *buf, int len, struct address *addr,
-		    struct hw_timestamp *hwts)
+static int raw_send(struct transport *t, struct fdarray *fda,
+		    enum transport_event event, int peer, void *buf, int len,
+		    struct address *addr, struct hw_timestamp *hwts)
 {
 	struct raw *raw = container_of(t, struct raw, t);
 	ssize_t cnt;
diff --git a/transport.c b/transport.c
index 3541394..ff5e307 100644
--- a/transport.c
+++ b/transport.c
@@ -42,24 +42,24 @@ int transport_recv(struct transport *t, int fd, struct ptp_message *msg)
 	return t->recv(t, fd, msg, sizeof(msg->data), &msg->address, &msg->hwts);
 }
 
-int transport_send(struct transport *t, struct fdarray *fda, int event,
-		   struct ptp_message *msg)
+int transport_send(struct transport *t, struct fdarray *fda,
+		   enum transport_event event, struct ptp_message *msg)
 {
 	int len = ntohs(msg->header.messageLength);
 
 	return t->send(t, fda, event, 0, msg, len, NULL, &msg->hwts);
 }
 
-int transport_peer(struct transport *t, struct fdarray *fda, int event,
-		   struct ptp_message *msg)
+int transport_peer(struct transport *t, struct fdarray *fda,
+		   enum transport_event event, struct ptp_message *msg)
 {
 	int len = ntohs(msg->header.messageLength);
 
 	return t->send(t, fda, event, 1, msg, len, NULL, &msg->hwts);
 }
 
-int transport_sendto(struct transport *t, struct fdarray *fda, int event,
-		     struct ptp_message *msg)
+int transport_sendto(struct transport *t, struct fdarray *fda,
+		     enum transport_event event, struct ptp_message *msg)
 {
 	int len = ntohs(msg->header.messageLength);
 
diff --git a/transport.h b/transport.h
index 05df53b..5c8a051 100644
--- a/transport.h
+++ b/transport.h
@@ -67,12 +67,12 @@ int transport_recv(struct transport *t, int fd, struct ptp_message *msg);
  * ptp_message itself is ignored.
  * @param t	The transport.
  * @param fda	The array of descriptors filled in by transport_open.
- * @param event	1 for event message, 0 for general message.
+ * @param event	One of the @ref transport_event enumeration values.
  * @param msg	The message to send.
  * @return	Number of bytes send, or negative value in case of an error.
  */
-int transport_send(struct transport *t, struct fdarray *fda, int event,
-		   struct ptp_message *msg);
+int transport_send(struct transport *t, struct fdarray *fda,
+		   enum transport_event event, struct ptp_message *msg);
 
 /**
  * Sends the PTP message using the given transport. The message is sent to
@@ -80,25 +80,25 @@ int transport_send(struct transport *t, struct fdarray *fda, int event,
  * address), any address field in the ptp_message itself is ignored.
  * @param t	The transport.
  * @param fda	The array of descriptors filled in by transport_open.
- * @param event	1 for event message, 0 for general message.
+ * @param event	One of the @ref transport_event enumeration values.
  * @param msg	The message to send.
  * @return	Number of bytes send, or negative value in case of an error.
  */
-int transport_peer(struct transport *t, struct fdarray *fda, int event,
-		   struct ptp_message *msg);
+int transport_peer(struct transport *t, struct fdarray *fda,
+		   enum transport_event event, struct ptp_message *msg);
 
 /**
  * Sends the PTP message using the given transport. The address has to be
  * provided in the address field of the message.
  * @param t	The transport.
  * @param fda	The array of descriptors filled in by transport_open.
- * @param event	1 for event message, 0 for general message.
+ * @param event	One of the @ref transport_event enumeration values.
  * @param msg	The message to send. The address of the destination has to
  *		be set in the address field.
  * @return	Number of bytes send, or negative value in case of an error.
  */
-int transport_sendto(struct transport *t, struct fdarray *fda, int event,
-		     struct ptp_message *msg);
+int transport_sendto(struct transport *t, struct fdarray *fda,
+		     enum transport_event event, struct ptp_message *msg);
 
 /**
  * Returns the transport's type.
diff --git a/transport_private.h b/transport_private.h
index 7530896..ec28e47 100644
--- a/transport_private.h
+++ b/transport_private.h
@@ -38,9 +38,9 @@ struct transport {
 	int (*recv)(struct transport *t, int fd, void *buf, int buflen,
 		    struct address *addr, struct hw_timestamp *hwts);
 
-	int (*send)(struct transport *t, struct fdarray *fda, int event,
-		    int peer, void *buf, int buflen, struct address *addr,
-		    struct hw_timestamp *hwts);
+	int (*send)(struct transport *t, struct fdarray *fda,
+		    enum transport_event event, int peer, void *buf, int buflen,
+		    struct address *addr, struct hw_timestamp *hwts);
 
 	void (*release)(struct transport *t);
 
diff --git a/udp.c b/udp.c
index 05c2ba0..3ac489e 100644
--- a/udp.c
+++ b/udp.c
@@ -215,9 +215,9 @@ static int udp_recv(struct transport *t, int fd, void *buf, int buflen,
 	return sk_receive(fd, buf, buflen, addr, hwts, 0);
 }
 
-static int udp_send(struct transport *t, struct fdarray *fda, int event,
-		    int peer, void *buf, int len, struct address *addr,
-		    struct hw_timestamp *hwts)
+static int udp_send(struct transport *t, struct fdarray *fda,
+		    enum transport_event event, int peer, void *buf, int len,
+		    struct address *addr, struct hw_timestamp *hwts)
 {
 	ssize_t cnt;
 	int fd = event ? fda->fd[FD_EVENT] : fda->fd[FD_GENERAL];
diff --git a/udp6.c b/udp6.c
index 7551e3f..12213d7 100644
--- a/udp6.c
+++ b/udp6.c
@@ -225,9 +225,9 @@ static int udp6_recv(struct transport *t, int fd, void *buf, int buflen,
 	return sk_receive(fd, buf, buflen, addr, hwts, 0);
 }
 
-static int udp6_send(struct transport *t, struct fdarray *fda, int event,
-		    int peer, void *buf, int len, struct address *addr,
-		    struct hw_timestamp *hwts)
+static int udp6_send(struct transport *t, struct fdarray *fda,
+		     enum transport_event event, int peer, void *buf, int len,
+		     struct address *addr, struct hw_timestamp *hwts)
 {
 	struct udp6 *udp6 = container_of(t, struct udp6, t);
 	ssize_t cnt;
diff --git a/uds.c b/uds.c
index 7e11f63..44d135f 100644
--- a/uds.c
+++ b/uds.c
@@ -108,9 +108,9 @@ static int uds_recv(struct transport *t, int fd, void *buf, int buflen,
 	return cnt;
 }
 
-static int uds_send(struct transport *t, struct fdarray *fda, int event,
-		    int peer, void *buf, int buflen, struct address *addr,
-		    struct hw_timestamp *hwts)
+static int uds_send(struct transport *t, struct fdarray *fda,
+		    enum transport_event event, int peer, void *buf, int buflen,
+		    struct address *addr, struct hw_timestamp *hwts)
 {
 	int cnt, fd = fda->fd[FD_GENERAL];
 	struct uds *uds = container_of(t, struct uds, t);