What is this?

This knowledgebase contains questions and answers about PRTG Network Monitor and network monitoring in general.

Learn more

PRTG Network Monitor

Intuitive to Use. Easy to manage.
More than 500,000 users rely on Paessler PRTG every day. Find out how you can reduce cost, increase QoS and ease planning, as well.

Free Download

Top Tags

View all Tags

Error connecting with SSL. EOF was observed that violates the protocol




When I enable "ProxyProtocol" in Apache2.4, our PRTG SSL Certificate sensor fails with the following: Failed to establish secure connection [Step 0] Error connecting with SSL. EOF was observed that violates the protocol

No other apps, browser nor clientsoftware seem to complain about this change in the Apache config - why does the PRTG fail?

apache eof proxyprotocol

Created on Oct 8, 2018 1:25:59 PM

3 Replies

Accepted Answer




from the doc https://roadrunner2.github.io/mod-proxy-protocol/mod_proxy_protocol.html you are not supposed to connect directly to an Apache port using the proxy_protocol so are your other users connecting to this Apache port or are they (as they should) connecting to Haproxy instead ? And is your prtg sensor connecting to Haproxy too or to the Apache port that should be normally blocked by firewall?

Created on Oct 9, 2018 8:58:27 AM



Hi there,

Unfortunately, our knowledge about Proxy Settings in an Apache Webserver is rather restricted. But could you check what gpfr has mentioned?

Best regards.

Created on Oct 9, 2018 10:17:32 AM by  Dariusz Gorka [Paessler Support]




Yes, GPFR is right. When using ProxyProtocol one cannot connect to the apache webservice thru anything but the haproxy, so the "error" makes perfect sense. I was wrong about client software not failing, my testing had been improper.


Created on Oct 9, 2018 10:56:07 AM

Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.