rdesktop session to RDP server hangs

I have noticed that when I leave my RDP session to Windows server open for a night, then in the morning session has hanged. For example I can't even type anything into password box: According to ps the status of rdesktop process is following: $ ps -o pid,ppid,state,time,command -fp 26638 PID PPID S TIME COMMAND 26638 26637 S 00:00:01 rdesktop -E -g 1920x1100 10.20.20.6 -a 32 -r clipboard:PRIMARYCLIPBOARD -r disk:windows /home/martin/windows -z -K $ However, under normal conditions, it is pretty much the same: $ ps -o pid,ppid,state,time,command -fp 30179 PID PPID S TIME COMMAND 30179 30178 S 00:00:02 rdesktop -E -g 1920x1100 10.20.20.6 -a 32 -r clipboard:PRIMARYCLIPBOARD -r disk:windows /home/martin/windows -z -K $ At first I thought that maybe my iptables/netfilter session times out, but this does not seem to be the reason because I inserted a rule which allows all the traffic from RDP server(10.10.10.1): Chain INPUT (policy DROP) target prot opt source destination ACCEPT all -- 10.20.20.6 anywhere What might cause this timeout? Is it possible that this timeout comes from RDP server side?