+typedef int (*gras_msg_cb_t) (gras_msg_cb_ctx_t ctx, void *payload);
+
+ /**
+ * @brief Bind the given callback to the given message type (described by its name)
+ * @hideinitializer
+ *
+ * Several callbacks can be attached to a given message type. The lastly added one will get the message first, and
+ * if it returns a non-null value, the message will be passed to the second one.
+ * And so on until one of the callbacks accepts the message.
+ *
+ * Using gras_cb_register is a bit slower than using gras_cb_register_ since GRAS
+ * has to search for the given msgtype in the hash table, but you don't care in most case.
+ */
+#define gras_cb_register(msgtype_name, cb) gras_cb_register_(gras_msgtype_by_name(msgtype_name),cb)
+
+ /**
+ * @brief Unbind the given callback to the given message type (described by its name)
+ * @hideinitializer
+ *
+ * Using gras_cb_unregister is a bit slower than using gras_cb_unregister_ since GRAS
+ * has to search for the given msgtype in the hash table, but you don't care in most case.
+ */
+#define gras_cb_unregister(msgtype_name, cb) gras_cb_unregister_(gras_msgtype_by_name(msgtype_name),cb)
+
+XBT_PUBLIC(void) gras_cb_register_(gras_msgtype_t msgtype,
+ gras_msg_cb_t cb);
+XBT_PUBLIC(void) gras_cb_unregister_(gras_msgtype_t msgtype,
+ gras_msg_cb_t cb);
+
+/** @} */
+
+/** @defgroup GRAS_msg_exchange Message exchange
+ * @ingroup GRAS_msg
+ *
+ */
+/** @{ */
+
+/** \brief Send the data pointed by \a payload as a message \a msgname on the \a sock
+ * @hideinitializer
+ *
+ * Using gras_msg_wait() is a bit slower than using gras_msg_wait_() since GRAS
+ * has to search for the given msgtype in the hash table.
+ */
+#define gras_msg_send(sock,name,payload) gras_msg_send_(sock,gras_msgtype_by_name(name),payload)
+XBT_PUBLIC(void) gras_msg_send_(gras_socket_t sock,
+ gras_msgtype_t msgtype, void *payload);
+
+/** \brief Waits for a message to come in over a given socket
+ * @hideinitializer
+ * @param timeout: How long should we wait for this message.
+ * @param msgt_want: type of awaited msg
+ * @param[out] expeditor: where to create a socket to answer the incomming message
+ * @param[out] payload: where to write the payload of the incomming message
+ * @return the error code (or no_error).
+ *
+ * Every message of another type received before the one waited will be queued
+ * and used by subsequent call to this function or gras_msg_handle().
+ *
+ * Using gras_msg_wait() is a bit slower than using gras_msg_wait_() since GRAS
+ * has to search for the given msgtype in the hash table.
+ */