Comment 12 for bug 1376483

I hit this bug with MAAS 2.1, the server fails commissioning.

rackd.log :

2016-11-03 16:36:05 [TFTP (UDP)] Datagram received from ('10.189.142.2', 1332): <RRQDatagram(filename=b'bootx64.efi', mode=b'octet', options=OrderedDict([(b'tsize', b'0'), (b'blksize', b'1468')]))>
2016-11-03 16:36:05 [-] RemoteOriginReadSession starting on 37207
2016-11-03 16:36:05 [-] Starting protocol <tftp.bootstrap.RemoteOriginReadSession object at 0x7fa1226dcda0>
2016-11-03 16:36:05 [RemoteOriginReadSession (UDP)] (UDP Port 37207 Closed)
2016-11-03 16:36:05 [RemoteOriginReadSession (UDP)] Stopping protocol <tftp.bootstrap.RemoteOriginReadSession object at 0x7fa1226dcda0>
2016-11-03 16:36:06 [-] Unhandled Error
        Traceback (most recent call last):
          File "/usr/lib/python3/dist-packages/twisted/application/app.py", line 364, in startReactor
            self.config, oldstdout, oldstderr, self.profiler, reactor)
          File "/usr/lib/python3/dist-packages/twisted/application/app.py", line 285, in runReactorWithLogging
            reactor.run()
          File "/usr/lib/python3/dist-packages/twisted/internet/base.py", line 1194, in run
            self.mainLoop()
          File "/usr/lib/python3/dist-packages/twisted/internet/base.py", line 1203, in mainLoop
            self.runUntilCurrent()
        --- <exception caught here> ---
          File "/usr/lib/python3/dist-packages/twisted/internet/base.py", line 825, in runUntilCurrent
            call.func(*call.args, **call.kw)
          File "/usr/lib/python3/dist-packages/tftp/util.py", line 81, in _call_and_schedule
            self.callable(*self.callable_args, **self.callable_kwargs)
          File "/usr/lib/python3/dist-packages/twisted/internet/udp.py", line 268, in write
            return self.socket.send(datagram)
        builtins.AttributeError: 'Port' object has no attribute 'socket'

tcpdump attached.