Debugging: ConnectionRefusedError with debugpy

[tseyde]

Environment data

• VS Code version: 1.43.1
• Extension version (available under the Extensions sidebar): 2020.3.69010
• OS and version: Ubuntu 16.04
• Python version (& distribution if applicable, e.g. Anaconda): 3.6, Anaconda

Error

File "/home/{user}/.vscode/extensions/ms-python.python-2020.3.69010/pythonFiles/lib/python/debugpy/no_wheels/debugpy/launcher/../../debugpy/launcher/__init__.py", line 27, in connect
    sock.connect(("127.0.0.1", launcher_port))
ConnectionRefusedError: [Errno 111] Connection refused

Work-around

Reverting back to previous version removes errors. The previous version uses "new_ptvsd" instead of "debugpy".

[int19h]

We'll need debugpy logs to diagnose this properly - can you please add "logToFile": true to your launch.json configuration, and then check ~/.vscode/extensions/ms-python* for files named debugpy*.log?

[int19h]

Also, can you try this with other Python versions (e.g. the global system one - /usr/bin/python3), and see if that still fails in the same manner?

[tysonpaul89]

I am also facing the same issue. I am also in Ubuntu 16.04 LTS.

I tried to downgrade the python extension to previous versions, but then the debugger will not start(no error shown on this case just. Terminal will show the initial debug command and it will not get executed).

The issue is there in python2.7 and python3.6 versions.

Debuggy logs for python2.7:

debugger.vscode_16c4c91a-991a-48dc-8838-ba4fb58349ae.log
debugpy.adapter-15275.log
debugpy.launcher-15285.log

Debuggy logs for python3.6:

debugger.vscode_5e68b1d1-d3f3-4248-a874-029aa309ad5d.log
debugpy.adapter-16073.log
debugpy.launcher-16097.log

I suspect this an OS related issue because on my laptop which is using Ubuntu 18.04 LTS doesn't have this issue.

This my launch.json.

{
   "version":"0.2.0",
   "configurations":[
      {
         "name":"Python: Current File",
         "type":"python",
         "request":"launch",
         "program":"${file}",
         "console":"integratedTerminal",
         "pythonPath":"/Projects/xxx/xxx/env/bin/python"
      },
      {
         "name":"Python: Django 8000",
         "type":"python",
         "request":"launch",
         "program":"${workspaceFolder}/manage.py",
         "console":"integratedTerminal",
         "pythonPath":"/Projects/xxx/xxx/env/bin/python",
         "args":[
            "runserver",
            "--noreload",
            "--nothreading"
         ],
         "django":true,
        "logToFile": true
      },
      {
         "name":"Python: Django 8001",
         "type":"python",
         "request":"launch",
         "program":"${workspaceFolder}/manage.py",
         "console":"integratedTerminal",
         "args":[
            "runserver",
            "8001",
            "--noreload",
            "--nothreading"
         ],
         "django":true,
         "logToFile": true
      },
      {
         "name":"Python Celery",
         "type":"python",
         "request":"launch",
         "program":"${workspaceFolder}/manage.py",
         "console":"integratedTerminal",
         "args":[
            "celeryd",
            "-Q",
            "cronJobQueueLow_LOCAL",
            "-l",
            "info",
            "-P",
            "solo"
         ],
         "django":true
      }
   ]
}

VSCode Version:

Version: 1.43.1
Commit: fe22a9645b44368865c0ba92e2fb881ff1afce94
Date: 2020-03-18T07:17:38.324Z
Electron: 7.1.11
Chrome: 78.0.3904.130
Node.js: 12.8.1
V8: 7.8.279.23-electron.0
OS: Linux x64 4.4.0-176-generic

Python Extension Version

Id: ms-python.python
Version: 2020.3.69010

[karthiknadig]

@tysonpaul89 I think your issue might be this one #87 Can you check the locale settings from the comments there and confirm?

[int19h]

Nope, judging by the logs, it's this one.

microsoft/vscode-python#10741 is almost certainly a dupe, although that one is on Windows.

[int19h]

microsoft/vscode-python#10793 is another manifestation.

[int19h]

The root cause for this is that we are using backlog=0 together with listen(). This normally results in a minimal connection queue size; but on Linux, if net.ipv4.tcp_syncookies is disabled, it literally means a queue of zero, so it can't accept any connections.

Until we ship the fix, the workaround is to set net.ipv4.tcp_syncookies to 1. This can be done one-off like so:

sudo sysctl -w net.ipv4.tcp_syncookies=1

However, it will not persist between reboots. To make it persistent, edit the same value in /etc/sysctl.conf.

[pawamoy]

microsoft/vscode-python#10741 was marked as duplicate of this issue, but this issue was resolved as a Linux issue, while I'm experimenting it on Windows. Should I open a new one?

[endlesslycurious]

Same here, issue is not resolved for Windows as only fix given by @int19h was for linux..

[int19h]

The error message in question is very generic - it can occur on many different code paths for many different reasons. It's preferable to file separate issues for these, and close the dupes later if investigation shows that the root cause is really the same.