Self-hosted build agent cannot connect to Azure DevOps Services, SSL connection could not be established

Question

Hello over the weekend my self-hosted build agent lost connection to the DevOps Services. Not completely but I am getting connection errors on almost all of my builds. my builds are failing with the error:

ERR Agent] System.Net.Http.HttpRequestException: The SSL connection could not be established, see inner exception.

---> System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host..

From the Agent diagnostic logs.

I tried re-installing the Agent but this is not possible either as I get the exact same error when I try to run config.cmd remove

I tried adding --sslskipcertvalidation but this does not seem to work with the remove command. I tried to remove the old from the services, but it will not remove from the agent machine as I cannot complete the "config.cmd remove" process.

No clue why I am getting these connection errors all of a sudden. (I am on the Basic plan) Does not seem to be relating to any current reported Azure outages (2021-04-12).

Answer 1

I ended up installing the agent again in a separate folder from the old agent. Likely the issue was that the old agent was installed with the url [org.name].visualstudio.com I guess there is now some SSL certificate issue on the old url. I installed the new agent with the dev.azure.com/[org.name] url and this solved all of my issues.

Answer 2

The same thing happened to me, but I was able to solve it by installing this application on the server, which is used to activate the TLS2 protocols with just one click and the SSL Cipher Suites

TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 (0x9f) DH 2048 bits FS 256
TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 (0x9e) DH 2048 bits FS 128

nartac IISCrypto is the app