Using vncwebsocket via API - LXC works while QEMU doesnt


Well-Known Member
May 6, 2018
Hi all

Been butting my head against the wall for the last few days over this issue. I was hoping if maybe someone has had the same and found a solution


1) We are using the API (tokens only, no cookies) to get the vnc credentials using the vncproxy endpoint with the added flag of websocket set as 1 (works on both LXC machines and QEMU)
2) Later we start the vnc websocket stream using the vncwebsocket endpoint with the returned vnc port, ticket and ticket for the password. This works flawlessly every time on all LXC machines, however doesnt work on any QEMU machines (all on the same node and set up)

I can see that the codebase in Proxmox is totally different between the LXC and QEMU vncproxy and vncwebsocket which is why I was wondering if anyone else had the same issue, or is this a bug?


Example of successful LXC connection:

Snippet from /var/log/pveproxy/access.log:

::ffff:138.84.555.555 - root@pam!zmy-api-user [03/06/2023:14:08:04 -0400] "POST /api2/json/nodes/my_node/lxc/105/vncproxy HTTP/1.1" 200 2639
::ffff: - root@pam!my-api-user [03/06/2023:14:08:09 -0400] "GET /api2/json/nodes/my_node/lxc/105/vncwebsocket?port=5903&vncticket=PVEVNC%3A647B8182%3A%3AiELyrwBfMqydIzb1wi4%2BCc1pr9rk8NYK8HGT5HMIfFFcqBfUaDpv3LnB8Mcokl%2FB46mleFl8u5LhN3seVYTIEL%2Flc6p%2FV9BJX1vvm8XKRMaZFvVD0eKZa9j%2BsscDltuqwFWgfGNBG%2F7gXQrBxa7D9WuoebpTHTacK9n0SirGFqvHugjh0jEN4OttKNci3970ViD6q86lt2tigZPMb8ZngO0IvHylAw5vNy%2BkZPcQrCJ43tHHHETUBAD0%2BvKRO4Can%2B7CSg9U8crubiDPj3TCBI2mN%2B1mdHPo1gzI6F3cT3rVvX7L1bBDr3%2BaA6aSaLSCB%2FW8Dck%2BAOyWY26sve%2BGyQ%3D%3D HTTP/1.1" 101 -

Logs from our reverse nginx reverse proxy (where all API tokens are injected)

  "time_local": "04/Jun/2023:06:13:41 +1200",
  "http_host": "",
  "remote_addr": "",
  "proxy_host": "",
  "upstream_addr": "",
  "upstream_uri": "/api2/json/nodes/my_node/lxc/105/vncwebsocket?port=5903&vncticket=PVEVNC%3A647B8182%3A%3AiELyrwBfMqydIzb1wi4%2BCc1pr9rk8NYK8HGT5HMIfFFcqBfUaDpv3LnB8Mcokl%2FB46mleFl8u5LhN3seVYTIEL%2Flc6p%2FV9BJX1vvm8XKRMaZFvVD0eKZa9j%2BsscDltuqwFWgfGNBG%2F7gXQrBxa7D9WuoebpTHTacK9n0SirGFqvHugjh0jEN4OttKNci3970ViD6q86lt2tigZPMb8ZngO0IvHylAw5vNy%2BkZPcQrCJ43tHHHETUBAD0%2BvKRO4Can%2B7CSg9U8crubiDPj3TCBI2mN%2B1mdHPo1gzI6F3cT3rVvX7L1bBDr3%2BaA6aSaLSCB%2FW8Dck%2BAOyWY26sve%2BGyQ%3D%3D",
  "upstream_status": "101"

As you can see the WebSocket 101 is all successful works great, while when trying using the same code, same set up, same node, same everything really but on a QEMU machine we get the following:

Example of non-successful QEMU connection:

::ffff:138.84.555.555 - root@pam!zmy-api-user [03/06/2023:14:00:04 -0400] "POST /api2/json/nodes/my_node/qemu/101/vncproxy HTTP/1.1" 200 2661

Note1: that only the vncproxy shows on up the /var/log/pveproxy/access.log, the actual vncwebsocket never shows up... I assume because it errors somewhere)
Note2: There is no errors at all or any logs showing up in syslog throughout the QEMU failed attempts on vncwebsocket endpoint

Logs from our reverse nginx reverse proxy (where all API tokens are injected) showing a 502 instead of the expected and success 101 on the LXC machines

  "time_local": "04/Jun/2023:02:06:09 +1200",
  "http_host": "",
  "remote_addr": "",
  "proxy_host": "",
  "upstream_addr": "",
  "upstream_uri": "/api2/json/nodes/my_node/qemu/100/vncwebsocket?port=5902&vncticket=PVEVNC%3A647B48C6%3A%3AflrdYsN7yymtllNtzAtXFQajNZFHc%2BnnAF9S8GpcVh0xxGJLRyvGz6thxEbJq26iWkQtpYWdqCfMJ1v7wx4N6iPgsPEKd06nj0%2BwBafoMHVnEABJCshXIMzhVd%2FXvEu7E35SWivfVxTJXTID7jz17EyAHecS8PGhLKrQJ2zFm3igFDpIEYmlkjYVRyZO68fIlGRGejyT0caXbkP8I7Q7bVsz14LIzdACOidkJyPX%2Beb8U5pyG7R3ElASbmFAZc4xOHNdZvmwncjK%2BcZxTHiuwp07RPxZvhOzY4qUReaJVIEDRD8J8AKOK8dC3lWYU%2BXXwXkBc%2BNdUXeBhgTLeZOjYw%3D%3D",
  "upstream_status": "502"


Does anyone know where I might be going wrong and if there is something different I need to do for QEMU vs LXC?

Thought it might be useful to also add our (slightly edited) nginx reverse proxy configuration snippet here. This is how we avoid using the cookies auth by simply proxy-ing the API Token to the requests + web-sockets (again, works perfectly with LXC but not with QEMU machines)

location / {
      proxy_pass https://pve_upstream_node:8006;
      proxy_set_header "Authorization" "PVEAPIToken=root@pam!zmy-api-user=XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX";

      proxy_http_version 1.1;
      proxy_set_header Upgrade $http_upgrade;
      proxy_set_header Connection "upgrade";
Last edited:


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