My workstation is located very close to my development server, so I don't have problem with the development server. However, my production servers are located at the data-center, and for some reason, my SSH connections (PuTTY) got broken after awhile.
Possible fix is to modify PuTTY setting. Look for "Seconds between keepalives (0 to turn off)" under the "Connection". Change it from the default value of 0, to another value (I use 20). This means, send one keepalive packet every 20 seconds.