Putty 'Server unexpectedly closed network connection' I have been getting the 'Server unexpectedly closed network connection' (see and Getting “Server unexpectedly closed network connection”) but it is not associated with any reboot, the connection just fails unexpectedly and with it, the web server (Apache) running off the Linux server. I use Putty through Windows 7 to connect to a Raspberry Pi running Raspbian. Any ideas what might be going wrong?
5 Answers
A PuTTY session left idle will disconnect at a time determined by the host server. Try enabling keep-alives in PuTTY. This causes PuTTY to send null SSH packets to the remote host periodically, preventing the session from timing out.
The PuTTY client can be configured to always establish a connection which will not time out due to inactivity. To create and save a new keep-alive connection, follow these steps:
- Open the PuTTY application, and go to the Options panel (labeled "Category") on the left of the window.
- Select (click) the "Connection" item.
- In the "Sending of null packets to keep the session active" area on the right, change the default value of "Seconds between keepalives" from 0 (turn off) to 1800 (30 minutes).
- Select the "Enable TCP keepalives (SO_KEEPALIVE option)" check box. Note: This option may not be available in older versions of the PuTTY client.
- On the topmost left side of the Options panel, select (click) "Session".
- In the "Host Name (or IP Address)" field, enter the destination host name or IP address (e.g., "destination.ipaddress.here.com" or "192.168.1.1").
- In the "Saved Sessions" text-entry box, provide a name for the session (e.g., "savedsession").
- Select "Save".
To use the modified session settings, select it from the "Saved sessions" list, then click the buttons marked "Load" and "Open".
If your connected sessions still time out, enter a lower number of seconds into the "Seconds between keepalives" value.
3The server could have been hardened. The reason could be a) the client ip may be not configured in /etc/allowhosts and/or b) unix/linux firewall rule/selinux is not permitting.
I had the same problem for a long time, I use putty to connect to AWS linux instances (some remote cloud servers) I read about fixing it with keepAlives in several pages several pages, tried it but to no avail.
And just yesterday, while looking for some color scheme settings I found this:
Besides adjusting the colors of the terminal it does apply some sane defaults (Like the forementioned KeepAlives to 59 seconds plus others), and guess what? I havent had any closed connection for two whole days.
I tried everything above and nothing worked until this
vi /etc/ssh/sshd_config
ClientAliveInterval 60
restart deamon sshdalso switched to kitty an alternative putty clone which is much better
1You were idle longer than the session timeout on the remote device, so it closed the session and PuTTy wasn't expecting it.
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