I have a notification set up in PRTG that is performing an http action to send notifications via slack webhook. Currently every time a sensor is put in an alarm state, the notification throws the following error:

Failed to establish secure connection [Step 0] Error connecting with SSL. Error connecting with SSL. error:140770FC:SSL routines:SSL23_GET_SERVER_HELLO:unknown protocol.

I've confirmed that the probe settings for monitoring requests are set to "auto" in the probe settings for monitoring in the prtg admin console. This issue started occurring out of nowhere last month and the webhooks currently are not working with slack.

Server Service: V18.2.41.1652 Probe Service: V18.2.41.1652


Article Comments

Hi there,

Did you changed anything like certificate your used TLS version in your network?


Apr, 2020 - Permalink

Hi,

Not recently no.


Apr, 2020 - Permalink

The error message indicates that the target device or a firewall in between rejects the connections. Did you already tested the webhook without PRTG (e.g. Powershell command "invoke-webrequest")?


Apr, 2020 - Permalink

Yes I don't have an issue there. There is no firewall preventing these connections. They are also working intermittently. My alerts worked all day yesterday but today the same alerts are returning the above error message on the same sensors in the same conditions. No network changes have been made from yesterday to today.


Apr, 2020 - Permalink

In this case, please enable the notification delivery logging and check the corresponding log file.


Apr, 2020 - Permalink

I'll get this set up and follow up.


Apr, 2020 - Permalink

Which logs am I looking for specifically? I have Debug, Sensor, System and Web Server logs. The Debug logs contain the following messages:

error:140770FC:SSL routines:SSL23_GET_SERVER_HELLO:unknown protocol [Step 3] Error connecting with SSL. Error connecting with SSL. error:1408F10B:SSL routines:SSL3_GET_RECORD:wrong version number [Step 4] Error connecting with SSL. Error connecting with SSL. error:1408F10B:SSL routines:SSL3_GET_RECORD:wrong version number [Step 5] Error connecting with SSL. Error connecting with SSL. error:140770FC:SSL routines:SSL23_GET_SERVER_HELLO:unknown protocol [Unsecure] IOHandler value is not valid


Apr, 2020 - Permalink

Hi,

You'll find the needed logs in the following folder path on your core server system C:\ProgramData\Paessler\PRTG Network Monitor\Logs\debug.


Apr, 2020 - Permalink

Those logs contain the message listed above. Could this be related to Slack deprecating TLS 1.0 and 1.1?

https://api.slack.com/changelog/2019-07-deprecate-early-tls-versions


Apr, 2020 - Permalink

Hi,

Could you please let me know if it is deprecated or will it be deprecated in the next times?


Apr, 2020 - Permalink

According to the article it is. However these notifications have been working for about a week with no issue. The problem started again yesterday. How can I find the ticket # of this case so I can submit the appropriate logs?

Thanks.


May, 2020 - Permalink

Hi,

Please us the following Ticket Number to provide us a support bundle: PAE2005761.


Kind regards Marijan


May, 2020 - Permalink