--- ./src/libmongoc/src/mongoc/mongoc-socket.c.orig	2018-10-04 10:03:55 +0200
+++ ./src/libmongoc/src/mongoc/mongoc-socket.c	2018-10-04 10:06:51 +0200
@@ -337,6 +337,11 @@
    ret = poll (pfds, nsds, timeout);
    for (i = 0; i < nsds; i++) {
       sds[i].revents = pfds[i].revents;
+#if defined(_AIX)
+      if (sds[i].socket->errno_ == ECONNREFUSED) {
+          sds[i].revents |= POLLHUP;
+      }
+#endif
    }
 
    bson_free (pfds);