How to maintain a persistent SSH connection?

[Phil Pennock]

On 2017-11-15 at 22:44 +0100, martin f krafft wrote:
> First, we need to debate to death whether it should be
> 
>   while sleep 1; do echo .; done
> 
> or
> 
>   while echo .; do sleep 1; done
> 
> ;)

Hah.  Clearly `while sleep N`, because that way killing the sleep
propagates the death out of the loop, making it easier to clean up
afterwards.  My bikeshed should be blue.

I realized afterwards that really, this is too frequent and also that I
didn't think through what ssh's default buffering behavior might be
without a PTY.

The simplest fix is thus to just use `ssh -t` to get line-buffering and
have each echo try to pass content to the client.

Otherwise, >> dd if=/dev/zero bs=1500 count=1 << is likely to work, but
at the cost of a chunk of unnecessary traffic.  Really, sacrifice a PTY
and let the systems all automatically decide to flush output on each
line.

-Phil