- send_call = &s;
-
- p.addr = addr;
- p.msg = msg;
- p.len = len;
-
- call SystemCall.start(&sendTask, &s, am_id, &p);
+ if (send_call == NULL) {
+ send_call = &s;
+
+ p.addr = addr;
+ p.msg = msg;
+ p.len = len;
+
+ call SystemCall.start(&sendTask, &s, am_id, &p);
+ send_call = NULL;
+ } else {
+ p.error = EBUSY;
+ }