[stunnel-users] keepalive and stunnel

Tue Jul 23 19:56:50 CEST 2013

On Tue, 2013-07-23 13:30:08 -0400, David H. Durgee wrote:
> I am attempting to use stunnel to provide secure telnet access to a  
> server on my system.  As it is possible that a user may be idle for long  
> period I have attempted to enable keepalive with stunnel.  My stunnel  
> conf files contain:
>
> socket = l:SO_KEEPALIVE=1
> socket = r:SO_KEEPALIVE=1
>
> on both the server and client side.  But wireshark shows no keepalive  
> packets being exchanged.  I am using socat to provide a service on the  
> LAN and connections using socat do show keepalive packets.  But to get  
> this working with socat I had to use the following:
>
> socat -d -d -L/var/lock/Port$PORT -  
> TCP:127.0.0.1:$PORT,keepalive,keepcnt=10,keepidle=3,keepintvl=1
>
> I had originally tried it with only the keepalive option, but it took  
> adding the other three options for it to work.  Perhaps this is  
> particular to my linux mint 13 maya x64 system and keepalive works by  
> itself on windows?  Are the other three options supported in stunnel?

`stunnel -sockets´ should show the available socket options and their
default values.

For the box I'm writing this mail from, the default for TCP_KEEPIDLE
is 7200 and for TCP_KEEPINTVL 75 (both in seconds).  You'll have to be
quite patient if you want to watch keepalive packets in wireshark
without tweaking the defaults ...

HTH,

Ludolf

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