Local process appears to be blocked until a remote connection is opened

This is a bit long winded so bear with me.

I have a Win Form application running on Win 7 (C# using .Net 4.6.1; EF 6). It monitors a web site and transfers some data to an SQL Server database running on the local network. It also transfer data through a terminal emulator (IBM PComms V6 using HACL which uses InterOps) to a Linux application (Centos 5 running on the local network). The application maintains 3 threads:- the main thread, a backgroundworker thread and another thread. The Win form obviously runs on the main thread. The web site monitor runs on the background worker and the Terminal emulator transfers run on the third thread. The application runs from 5am and goes to sleep around 8pm and wakes up at 5am the next morning This application has been running since 2011 with out issue.

However, about a 9 months ago it development the following issue. The wake up occurs as normal at 5am but the attempt to login to the Linux application proceeds with the a Login prompt, which is responded to with an existing user login, and then there is no password prompt from Linux. The application traps this exception and continually cycles ever 2 minutes trying to login with the same set of results i.e. not login prompt .... Until I remotely connect (using RDP) at any time after 5am and then the next login cycle works with nothing having happened except apparently the remote login.

Obvious thoughts:-

  • Something is preventing logins on the Linux system - does not seem to be the case as it is prompting for login and also because as soon as the remote connection is made the login process occurs as normal.

  • Linux Credentials issues - the credentials work continuously through out the day in 2 minute cycles.

  • The PC is sleeping - not the case as the logs for the application show the continuous cycling and attempts to login (the IBM PComms has a function to copy the terminal emulator presentation screen which I write to a log and this log show the Linux login prompt, my apps response with a user login name and no password prompt).

  • Wait longer for the password prompt - I have set the application to wait for up to 120 seconds - it is currently set to 10 seconds waiting for the password prompt

  • The Linux system is sleeping - not the case for the same reason as above - i.e. I am getting a login prompt.

If any one has any ideas, as to possibilities for what may be causing this strange set of events, so that I can investigate further, they would be much appreciated. :-)

Thanks in advance