Wednesday, February 24, 2016

Mosh and SSH

I recently gave mosh a try. I'd read a bit about how useful it can be with unreliable connections and queuing commands and maintaining a local echo to screen as you type avoiding lag - all good stuff.

However using GNU screen (or tmux) solves a lot of the problems with reconnecting so I just never bothered. I was also under the impression that mosh and ssh were mutually exclusive when in fact they both work together. I was  concerned that installing mosh might break or hamper an exiting reliable ssh service. Well so far I've installed it on several systems and it's has no negative effects on sshd. And that's the point of this post. I could not find that information written anywhere on the web.

That's not to say it's been perfect. It is possible to orphan a mosh session to which you cannot reattach. That is a bit annoying if rare. It doesn't aid scp and  sftp transfers in terms of resumes. But that limitation doesn't bother me. Also there is no mosh support in putty (nor is there likely to be!) or its forks such as kitty which is disappointing if you use any windows systems. There are some mosh clients for windows but they're crippled versions of free or commercial packages or buggy cygwin hacks. Not against payware - there just isn't one around I like the look of.

On mobile platforms however, JuiceSSH implements mosh admirably. Highly recommended on the Android platform.

Mosh monitors active ssh connections on a high port so port 22 or equivalent isn't enough. It requires upd on an additional high port (~60001) to be opened on firewall etc. 

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