The user_port.txt files contain connection information to the SystemLink tray application for a separate Windows user login. In the rare case that the SystemLink client computer is running a Windows Server operating system, which supports multiple concurrent user sessions, each user session has a separate instance of the SystemLink tray application. Each time the SystemLink client runs a salt job (such as the Refresh job), the SystemLink tray application displays the job status. These user_port.txt files store the connection information for the SystemLink Client software to notify these multiple SystemLink tray application instances.
After each salt job is executed, the SystemLink Client software tries to notify each of these user_port.txt tray application instances, one after another, with a 2 second timeout. Prior to SystemLink Client 21.5.4, there was nothing to stop these user_port.txt files from accumulating as different users logged onto the SystemLink client. More user_port.txt files mean the SystemLink tray application notification stage after each salt job takes longer and longer-- roughly twice the number of user_port.txt files in seconds. Since the SystemLink Server only waits 30 seconds for the return signal from the SystemLink client on each Refresh job, you can end up in a state where the SystemLink Server assumes each Refresh job failed, when in fact they are just taking longer than 30 seconds to complete successfully.
The SystemLink Client 2022 Q1 Patch 4 (21.5.4) software has a fix to immediately delete any user_port.txt file that fails to connect to a SystemLink tray application instance. This self-healing mechanism will automatically keep the number of user_port.txt files low enough not to significantly affect the timing of the Refresh job response. Any SystemLink Client version after SystemLink Client 2022 Q4 will also have this fix in it.
For versions that do not include the fix, go to the C:\ProgramData\National Instruments\Systems Management\NIMinionConfig\ports\ folder on the SystemLink client computer and delete all the user_port.txt files there except the one that corresponds to the currently logged in user.
After deleting the unneeded user_port.txt files, wait a minute or two for the SystemLink Server to re-try the Refresh job on the affected SystemLink client, or alternatively go to the SystemLink Server systems page and click on the More>>Refresh menu for that SystemLink client to force the Refresh job to start.