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The underlying connection was closed: An unexpected error occurred on a receive

Article # 3031402 - Page views: 1746


The RSA is showing the following error messages:

The underlying connection was closed: An unexpected error occurred on a receive.


(500) Internal server error. The remote server returned an error: (500) Internal server error.


This error frequently is caused by trying to synchronize a file too large for the IIS server to accept.

The file could be large for several reasons:

  • eDocuments individually larger than 4 MB
  • Scanned documents with single pages larger than 4 MB (unlikely)
  • A Batch of scanned documents with so many pages that the accompanying XML file describing them is greater than 4 MB


The following solutions below still apply to IIS 10:


Methods to increase this cap or deal with it though the IIS changes are specifically related to IIS 6 and previous.

As in IIS 6, the maxRequestLength is, by default, capped at 4 MB. This can be locally changed for the ACIS application by editing its web.config file. This is usually located at: C:\Program Files\KCN Server\Bin\Web.

Under system.web, add the line:

<httpRuntime maxRequestLength="204800" executionTimeout="600"/>


The value of maxRequestLength is in kilobytes. ExecutionTimeout is in seconds.


IIS 7 and 8.x introduces an additional constraint, also configurable in the web.config file.

It requires the addition of a new section:




            <requestLimits maxAllowedContentLength="209715200"></requestLimits>





The value of maxAllowedContentLength is in bytes.


After changing these values, you must perform an IISRESET for the Web server to adopt the changes.

At the Remote Site

  1. Stop the RSA (as a task or service)
  2. Back up and edit the ACConfig.XML file's ACIServer tag:



     <ACIServer RemoteSite="1" />



  <ACIServer RemoteSite="1">




3. Restart the RSA and test by uploading large Batches.


At the Central Site (on all IIS servers running the Kofax Capture Network Server software):

1   In IIS Manager, right-click on the ACIS virtual application and select Properties.

2   On the Virtual Directory tab, click the Configuration... button.

3   Select the Options tab. Change the "ASP script timeout" value from 90 to 300 and apply this change.

4   Back up and edit the Program Files\KCN Server\Bin\Web\Web.config file as follows:

a. Within the <system.web> tag, add the following parameter as the first entry:

                <httpRuntime maxRequestLength="102400" executionTimeout="300" />

NOTE: The default maxRequestLength is 4096. Please set the maxRequestLength appropriately for your configuration.

b.      Within the <appSettings> tag, modify the existing parameter:


<add key="forwardertimeout" value="180" />


<add key="forwardertimeout" value="300" />


5  Restart IIS via a command prompt (IISReset) or by right-clicking "Internet Information Services (IIS) Manager" in Computer Management ¦ All Tasks ¦ Restart IIS.

Accept the default value ("Restart IIS on <machineName>")


NOTE: The value of the Maximum Request Length (maxRequestLength) parameter is in bytes (B), not kilobytes (KB). Some of Microsoft’s documentation incorrectly notes that value of this parameter measured in kilobytes.


The following is optional and recommended (for large files sent to Remote Sites):

6  Back up and edit the AConfig.XML file. Within the ACConfig.XML file's "<ACI Server>" section, add the following parameter (a restart of the KCNS services is required):



(NOTE: this option only compresses the Batch.XML file into a CAB file. The other XML files and Batch images are not affected. There is no option to configure compression of image files at the Central Site.)

In some cases, this error has been seen to occur when a Batch has a large number of Documents. It's been noted (in some cases) that the following edit to the Registry resolved the issue:

1  Create a new string value (see the value at the end of this path):

HKLM\SOFTWARE\Kofax Image Products\Ascent Capture\3.0\RsaCompressXmlFiles.

2  Set the value to 1.

3   Similarly, RsaCompressImages can also be created to send images in a package rather than individual files. Set this value to 1 to enable.


NOTE: These two settings affect uploads from Remote Sites only. Downloads are not affected.



Level of Complexity 



Applies to  

Product Version Build Environment Hardware
Kofax Capture 11.x N/A N/A N/A


13824, 11271, 11020


Article # 3031402
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