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Expectation Failed error 417 when connecting through a proxy


QAID # 15475 Published

Question / Problem:

I receive a COM error connecting to the license server, but when I turn off the proxy it works. If the proxy is on, I receive the following error message:

7001 ACLicClnt Unable to connect to license server. The license server may be down or the network may have problems (The remote server returned an error: (417) Expectation Failed.)

Answer / Solution:

This error can be caused when there is a proxy in place and it is not configured to handle HTTP "expect100" requests or return "100 (Continue)" on port 2424 used for licensing.

When a module opens and contacts the license server, it sends a header to the license server and expects to receive a "100 (Continue)" response before sending the body of the licensing request. Because the proxy server does not send "100 (Continue)" back to the client, the "Expectation Failed" licensing error is produced.

Possible workarounds include:

  • Disable the proxy server for local addresses.
  • Configure the proxy server to allow "expect100" status and "100 (Continue)" responses on port 2424.
  • Use a fully qualified hostname referencing the license server host in the AcConfig.xml file.
  • Use an IP address referencing the license server host in the AcConfig.xml file.

Ultimately, this is a proxy server configuration problem which should be resolved.

Applies to:

Product Version

Keywords: 417 expectation failed, 100 Continue, 100Continue, 100-Continue, Expect100, Expect-100, Expect 100