spawn id not open. connection closed by foreign host

spawn id not open. connection closed by foreign host

I am facing a problem .when i try to run some scripts(tcl) on a hardware
device(switch cards) scripts are running and then i try to save the config
and add some sleep time to reboot the switch card .When i again try to run
those same scripts after sleep interval it shows "*
connection closed by foreign host and send spawn id 12 not open.Then it
exits execution.
*". Is it because my telnet session expires after some time or what? .I
cant find out the solution why this spawn id closed message is coming.