This error message indicates that the connection to the remote host computer has been lost. There may be problems with the configuration or the physical setup of the network connections of either your computer or the remote host computer.
It is also possible that the remote host computer has been rebooted, which has disconnected your computer from the host.
Usually problems of this kind are temporary, and you can try again after waiting for a while. If this does not help, check your local network connections, and if necessary, contact also the system administrator of the remote host computer.