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Article ID: 126995, created on Sep 24, 2015, last review on Jul 14, 2018

  • Applies to:
  • Plesk Automation 11.5


During attempt to download a file by using File Manager in Customer Control Panel the following error message appears randomly:

Error: Unable to show file file.txt: The error 'SSL read: errno -5961' occurred during the connection to the agent at ''. 

where is IP address of the IIS service node used for hosting the website.


Currently, Plesk Automation management node uses TLS 1.2 to communicate with service nodes. By default during management node deployment PA installs libcurl library that uses openssl engine that implement TLS 1.2 compatible with Microsoft IIS 8.5. However, if libcurl library was downgraded to a version that uses NSS engine, this causes the aforementioned issue.

The libcurl could be downgraded in order to apply the workaround from the following KB article:

KB126384 Cannot download the file through file manager

Such behavior has been considered as a software issue #PPA-2725 and will be fixed in future product updates.


As a temporary workaround the JsonRpc.php file can be replaced in order to use TLS 1.1 for communications between management node and service nodes:

  1. SSH to the management node
  2. Download the JsonRpc.php file

    # wget
  3. Create backup of the existing one:

    # mv /usr/local/psa/admin/plib/Service/Agent/Transport/JsonRpc.php{,.orig}
  4. Copy the downloaded file to /usr/local/psa/admin/plib/Service/Agent/Transport/:

    # cp JsonRpc.php_TLS1.1 /usr/local/psa/admin/plib/Service/Agent/Transport/JsonRpc.php

If the workaround does not work, make sure that TLS 1.1 is enabled on the IIS node:

at HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols add the following:

key: TLS 1.1 in TLS 1.1 add: create the DWORD Values under Server and Client key as following

DisabledByDefault [Value = 0] Enabled [Value = 1]


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