While running the Python code, it shows ConnectionRefusedError: [Errno 111] Connection refused

Hi, dear PYNQ developers,

We use ZCU-104 for hardware accelerator development now. In the initial testing, the python test code can load the image and test the hardware on the ZCU-104.

Then, our SW team takes over the board for other SW installation, etc. Two months later, while I revisited the ZCU-104 platform and would like to re-run the previous PASSed test, it occurred the following error as shown below.

However, I have no idea what is the possible cause and thus I don’t know how to debug. Do you know where does the socket lie on the disk? Or maybe a problem with changed IPs? Would you please shed some light to make me carry on debugging? Thank you very much.

xilinx@pynq_sdu:~/pynq/prj_tst/dual_utst $ sudo python3.6
[sudo] password for xilinx:
INFO: FPGA overlay class loading time: 3.7525856494903564

Traceback (most recent call last):
File “”, line 78, in
overlay = Overlay(ol_path)
File “/usr/local/lib/python3.6/dist-packages/pynq/”, line 315, in init
File “/usr/local/lib/python3.6/dist-packages/pynq/”, line 379, in download
File “/usr/local/lib/python3.6/dist-packages/pynq/”, line 1938, in download
File “/usr/local/lib/python3.6/dist-packages/pynq/”, line 1458, in shutdown
ip = cls.ip_dict
File “/usr/local/lib/python3.6/dist-packages/pynq/”, line 1297, in ip_dict
File “/usr/local/lib/python3.6/dist-packages/pynq/”, line 1416, in client_request
cls._remote = Client(address, family=‘AF_UNIX’, authkey=key)
File “/usr/lib/python3.6/multiprocessing/”, line 487, in Client
c = SocketClient(address)
File “/usr/lib/python3.6/multiprocessing/”, line 614, in SocketClient
ConnectionRefusedError: [Errno 111] Connection refused
Tue 22. Dec 08:44:01 AM UTC 2020 ✘ ❬1❭
xilinx@pynq_sdu:~/pynq/prj_tst/dual_utst $

All the best,

It is difficult to know what is going wrong here without knowing what has changed. Can you revert back to a fresh image of PYNQ and test your design on it?
I also noticed from your other post that you seem to be using an older version of the PYNQ image. You may want to try the latest version. You will need a HWH and not the Tcl file from your Vivad design.


It seems that you are trying to authenticate using public key.

Is the public key available in the other node? Is public key authentication enabled?
Can you ssh to the other node? Can you ping to the other node?