After starting Turtlebot machine with

roslaunch turtlebot_bringup minimal.launch --screen

it works fine for about 10 to 15 minutes, then the following error message start to show up on the screen

[ERROR] [WallTime: 1500666636.971771] Interactions : socket error trying to retrieve information from the local master.
[ERROR] [WallTime: 1500666754.493259] Interactions : socket error trying to retrieve information from the local master.
[ERROR] [WallTime: 1500666762.952144] Interactions : socket error trying to retrieve information from the local master.

.

just start to appear recently!