To modify an existing session with "keep alives" to maintain your connection follow the steps below:
- Open the PuTTy application and navigate to the Options panel.
- Load the session definition by selecting it from the list.
- Click Load
- Select Connection
- In the field Sending null packets to keep session active change the default value from 0 to 1800 (30 minutes)
- Check the Enable TCP keepalives (SO_KEEPALIVE option) check box.
Note: This option may not available in older versions of the PuTTY client.
- Select Session from the left hand menu
- Select Save
Any new sessions will now use these modified connection options.
configure PUTTY to not time out
原文：http://www.cnblogs.com/miaoz/p/3995935.html
