Comment 5 for bug 1260893

The problem was caused by starting a thread and then forking the program as part of daemonizing it. This resulted in the thread no longer communicating correctly with the forked main program. See here for more information:

http://www.linuxprogrammingblog.com/threads-and-fork-think-twice-before-using-them

I've created a patch that fixes this problem by creating the daemon fork prior to creating any threads. This has worked OK in my limited testing, but I recommend additional testing before releasing this version on an unsuspecting world.

Note also that iperf2 appears to be semi-deprecated in favor of iperf3, which is not yet in Ubuntu. From the iperf2 Sourceforge page: This is the old, Iperf 2 code base. The primary development has moved to Iperf 3 which is hosted on Google Code. You can find it here: http://code.google.com/p/iperf/." It appears that efforts are underway to bring iperf3 into Debian:

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=739921