企业 VPN 阻止 websocket

Question

我在工作中有一个服务器，我登录该服务器以使用 jupyter 笔记本进行数据科学项目。多年来，无论是连接到校园 wifi 还是通过 VPN 远程连接，它都一直正常工作。现在，经过一些网络升级后，我仍然可以通过校园 wifi 连接，但通过 VPN 连接时，WebSocket connection to 'ws://server.internal/notebook/api/kernels/af23e3bf-65a7-47d4-8ad0-1afce22997f6/channels?session_id=5d17ad5ef8374ba4bff8f10d0e1ba3e4' failed:控制台中会出现错误，导致出现错误窗口，提示Connection failed A connection to the notebook server could not be established. The notebook will continue trying to reconnect. Check your network connection or notebook server configuration.

我使用以下方式启动笔记本进程jupyter notebook --no-browser --notebook-dir=/data2 --ip=0.0.0.0 --port=8889

并使用 nginx 连接到笔记本服务器，配置如下

server {
        listen 80;
        listen [::]:80;

        root /var/www/server.internal/html;
        index index.html index.htm index.nginx-debian.html;

        server_name server.internal;

        location / {
                try_files $uri $uri/index.html;
        }

        location /notebook {
                proxy_pass http://localhost:8889;
                proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
                proxy_set_header X-Real-IP $remote_addr;
                proxy_set_header Host $http_host;
                proxy_http_version 1.1;
                proxy_redirect off;
                proxy_buffering off;
                proxy_set_header Upgrade $http_upgrade;
                proxy_set_header Connection "upgrade";
                proxy_read_timeout 86400;
                client_max_body_size 100m;
                error_log /var/log/nginx/server_err.log debug;
        }

在我的 nginx 日志中，我会看到一些错误，例如

2021/06/08 14:22:17 [error] 2258#2258: *1 connect() failed (111: Connection refused) while connecting to upstream, client: 172.22.124.52, server: server.internal, request: "GET /notebook/api/sessions?_=1623089993100 HTTP/1.1", upstream: "http://[::1]:8889/notebook/api/sessions?_=1623089993100", host: "server.internal", referrer: "http://server.internal/notebook/tree/helen_mixed_infection/notebooks"

我的 jupyter 日志中没有出现任何错误，所以我认为这是一个网络问题，但想知道是否有办法解决它。