I upgraded burpui from 0.5 to 0.6.1. Thanks for the new version ! Server is Ubuntu 16.04, nginx v1.10 at port 443 is setup as reverse proxy.

Some issues:

a. Errors in nginx log

2018/06/06 15:58:08 [error] 28085#28085: *9 connect() failed (111: Connection refused) while connecting to upstream, client: aaa.bbb.ccc.ddd, server: xyz.informatik.uni-kiel.de, request: "GET /api/clients/backup-running?_session=db865
af9-7043-48ad-a3b4-576fbbfeeb01&_extra=1528291021.0 HTTP/1.1", upstream: "http://[::1]:5000/api/clients/backup-running?_session=db865af9-7043-48ad-a3b4-576fbbfeeb01&_extra=1528291021.0", host: "xyz.informatik.uni-kiel.de", referrer: "
https://xyz.informatik.uni-kiel.de/about"

b. How do I see wether [WebSocket] is working properly ? I added it to the nginx configuration as a reverse proxy. What is the value for the url entry in burpui.cfg for this configuration ?

        server {
                listen 80;
                server_name xyz.informatik.uni-kiel.de;

                rewrite     ^   https://$server_name$request_uri? permanent;
        }


        server {
                listen 443 ssl;
                server_name xyz.informatik.uni-kiel.de;

                ssl_certificate /etc/letsencrypt/live/xyz.informatik.uni-kiel.de/fullchain.pem;
                ssl_certificate_key /etc/letsencrypt/live/xyz.informatik.uni-kiel.de/privkey.pem;

                access_log  /var/log/nginx/burpui.access.log;
                error_log   /var/log/nginx/burpui.error.log;

                location / {

                        # you need to change this to "https", if you set "ssl" directive to "on"
                        proxy_set_header   X-FORWARDED_PROTO https;
                        proxy_set_header   Host              $http_host;
                        proxy_set_header   X-Forwarded-For   $remote_addr;

                        proxy_read_timeout 300;
                        proxy_connect_timeout 300;

                        proxy_pass http://localhost:5000;
                }

                location /socket.io {
                        proxy_http_version 1.1;
                        proxy_buffering off;
                        proxy_set_header Upgrade $http_upgrade;
                        proxy_set_header Connection "Upgrade";
                        proxy_pass http://127.0.0.1:5001/socket.io;
                }
        }

c. gunicorn error

[2018-06-06 16:10:58 +0000] [28007] [ERROR] Error handling request
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/gunicorn/workers/async.py", line 110, in handle_request
    resp.write_file(respiter)
  File "/usr/lib/python2.7/dist-packages/gunicorn/http/wsgi.py", line 397, in write_file
    if not self.sendfile(respiter):
  File "/usr/lib/python2.7/dist-packages/gunicorn/http/wsgi.py", line 387, in sendfile
    sent += sendfile(sockno, fileno, offset + sent, count)
  File "/usr/lib/python2.7/dist-packages/gunicorn/workers/ggevent.py", line 38, in _gevent_sendfile
    return o_sendfile(fdout, fdin, offset, nbytes)
  File "/usr/lib/python2.7/dist-packages/gunicorn/http/_sendfile.py", line 67, in sendfile
    raise OSError(e, os.strerror(e))
OSError: [Errno 32] Broken pipe

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