+#define CREDIT_OK 1
+#define CREDIT_FAIL -1
+
+#define REQUEST_OK 1
+#define REQUEST_NO_MONEY -1 /* insufficient credit */
+#define REQUEST_SERVFAIL -2 /* server did not respond */
+#define REQUEST_EMPTY -3 /* none of item left */
+#define REQUEST_INVAL -4 /* no such item */
+