keep ssh connection alive

It is very annoying when I look up something in a different window and then switch back to the ssh terminal only to find out that the connection has timed out and I need to log in again. One way to solve this is to send null packets at regular intervals from the client side. Open the ~/.ssh/config file and add the following lines:

Host example
    Hostname example.com
    Port 22
    User username
    ServerAliveInterval 240
    ServerAliveCountMax 2

Replace example with a label for the connection, example.com with the hostname and username with the remote username. ServerAliveInterval value of 240 means that it will send null packets every 240 seconds to keep the connection alive. According to ServerAliveCountMax, the ssh client will close the connection if it does not receive a response after two tries. rtfm man ssh_config.