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Titre
RemoteScan locking up at Reading Image step when utilizing Citrix ICA -
Description
Issue where RemoteScan intermittently locks up at Reading Image step when utilizing Citrix ICA.
To verify this precise issue is happening, in RemoteScan logging:
Look for ‘Socket Closed before Quit’ inside RemoteScan Server log at the time of occurrence:
Look for 'Error Writing to sockProxy" inside RemoteScan Server proxy log at the time of occurrence:
RemoteScan Server logging can be enabled on the local Citrix client. To enable logging, right-click on RemoteScan tray icon on the local PC and click on Options. In the RemoteScan Server options window, check the checkbox for Logging and then click Save to close the options window.
Once RemoteScan Server logging is enabled, the log can be retrieved by navigating to the user's AppData folder at:
C:\Users\User1\AppData\Local\RemoteScan\logs -
Cause
This issue has been identified by Citrix support as being provoked by RemoteScan's use of a dynamically-sized packet buffer when utilizing an ICA virtual channel. Any packets sent over an ICA virtual channel over 4996 bytes are automatically discarded.
Previously, if ICA dropped a RemoteScan data packet, RemoteScan could be configured to automatically retrieve the lost packet using rensendenabled=1 (workstation setting) and/or resendtoserver=1 (remote session setting).
However, Citrix implemented a 4996-byte cap for packet size beginning with XenApp 7.15 LTSR, and has maintained this maximum packet size requirement for subsequent versions of Citrix VDA. Therefore, if an application attempts to send a data packet over 4996 bytes across an ICA virtual channel, the packet may be irretrievably dropped.
When this occurs, users may experience unexpected interruption in their scanning workflow, since the RemoteScan ICA virtual channel connection gets unexpectedly severed with no mechanism for recovery.
However, this issue was repaired in RemoteScan version 10.828, as controls were introduced in this RemoteScan version to ensure packets transmitted over ICA do not exceed 4996 bytes.
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Résolution
Upgrade both RemoteScan Server and RemoteScan Client to version 10.828, or higher.
If the upgrade was applied to the above recommended version, please verify the upgrade was successful by reviewing the NTFS file version of the following files:
In individual user's home path on Citrix server user profile, verify the following file version:
%HOMEPATH%\Windows\Twain_32\RemoteScan\RSICAServerProxy.dll (needs to be version 2.2.0.8)On the Citrix client, verify the following file version:
C:\Program Files (x86)\Citrix\ICA Client\vdRSIWSPl.dll (needs to be version 2.2.3.2)
Additional Citrix References:Citrix reference regarding max packet size:
According to Citrix, regarding maximum packet size:
"if the server is running XenApp, the maximum packet size is 5000 bytes (4996 bytes of data plus the 4-byte packet overhead generated by the ICA datastream manager). If more data is received that the buffer can hold, the entire packet is discarded. If no data is received pBuffer and pBytesRead are unmodified. The function fails if the read times out."
https://developer-docs.citrix.com/projects/receiver-for-windows-virtual-channel-sdk/en/latest/programming-reference/
(Citrix Virtual SDK programming reference, published March 6, 2017)
Citrix reference regarding large data streams:
According to Citrix:
"Session interactivity is constantly measured to determine whether any data streams within the ICA session are adversely affecting interactivity. If that occurs, the throughput is decreased to reduce the impact of the large data stream on the session and allow interactivity to recover."
https://docs.citrix.com/en-us/citrix-virtual-apps-desktops/1912-ltsr/technical-overview/hdx.html
(Citrix Virtual App 1912-ltsr technical overview, published May 7, 2021) -
Informations supplémentaires
This situation is also being investigated internally under the following reference number RS-16.
