TCP server dies after few hours of inactivity

We have a NAS application which can be accessed by both HTTP and HTTPS connections.
The issue we are facing is that the tcp server instance that initiates the HTTP access dies after a few hours of inactivity(the NAS application was kept idle for around 10 hours). However, the tcpserver that launches HTTPS connections remained running.So the connection failed through HTTP access but the connection succeeded through HTTPS access.
The converse has also been observed where the tcpserver for HTTPS is dead but tcpserver for HTTP is running.
The version of tcpserver that we are using here is ucspi-tcp-0.88.tar.gz.
I have the following queries:
a)Has anyone faced the same problem before?
b)Is it an issue with this package version of tcpserver ?
c)Will upgrading to newer versions of tcpserver bail me out of the issue?
d)Also, could anyone let me know what are the possible causes for the tcpserver to die ?

The system logs might let you know if the program crashed etc. Its own logs might tell you if it halted suddenly or did a graceful shutdown for some reason. Other things to kill it could be the IP address changing, or the interface going down and up, but those aren't likely to happen to a server.