Do EZTwain/EZTwainX work under Citrix or Windows Terminal Services?
When a program runs under Citrix/Terminal Services, it is of course running on a server but 'thinks' it is running on a client workstation. The question is - how does scanning work in this emulated environment? Under Windows Terminal Services (WTS), TWAIN is generally not available: The TWAIN DataSource Manager (DSM) is typically not present at all.
Citrix, starting with Presentation Server 4.0 (PS), provides some level of TWAIN redirection: This means that TWAIN requests by an application are redirected through PS to the client workstation where they are routed to the client's local TWAIN devices. We think that Citrix put significant care and effort into their TWAIN Redirector, unfortunately it works with only some scanners. Several customers have found scanners that work perfectly outside of the Citrix session, but scanning hangs from an application in a Citrix session.
We do not support scanning under WTS unless you use a 3rd party TWAIN 'remoting' solution such as RemoteScan. Under Citrix, we encourage customers to experiment if they have specific scanners: Many will work. However, if your scanning code fails inside of Citrix but works outside, we may not be able to resolve the problem.
References
TWAIN Redirection Support with Presentation Server 4.0
Troubleshooting TWAIN with Citrix Presentation Server 4.0