"No buffer space available" when sending on Mac OS

When sending multicast messages (with MPerf & fast.xml), the following message appears:

8981 [ERROR] UDP: JGRP000029: A: failed sending message to cluster (1053 bytes): java.io.IOException: No buffer space available, 
headers: MPerf: DATA999, NAKACK2: [MSG, seqno=1003], UDP: [cluster_name=mperf]

The messages are received, but the error message occurs on almost every message (1 sender thread sending 1000 messages).

With UdpPerf (also shipped with JGroups), which also multicasts messages, the error doesn't happen.

With UPerf, which uses unicasts, the error doesn't occur either.

Todo: compare UdpPerf to MPerf (UDP protocol) to see what the diff is.