SSH pairing tunnels with Tmux and ngrok

My team has been playing with the idea of remote programming and what that would look like, especially for longer periods of time (e.g. remoting from Germany for a month or two =). In the office, we don't often pair program unless we need some feedback or want to check out each other's code. Despite not paring very often, I thought I'd look into some options in case the time came.

Now, you could use something like and screen share. But (1) that's just not very cool. And (2) It can be slow and glitchy. Our entire team uses VIM now, so I thought I'd try out session sharing with something like tmux. After installing a couple items you can get up and running in no time, sharing a terminal window at lightning speed. Here was my process to get this up and running (I'm using OSX here).

1. Install Tmux

Tmux allows you to manage multiple terminal windows into one, almost like using vim splits. You can also share sessions with it, which is what I'll be using it for.

$ brew install tmux

2. Authorize users with github

You'll need to allow users to ssh into your machine. Instead of giving them my password or creating a user for them, I'm going to use their ssh key. You can set it up manually, or for Github users there's a nifty gem for that. Github apparently stores all the public keys you add to it... publically ( The gh-auth gem. makes use of this so we can add and remove user keys super easily.

$ gem install github-auth

Auth a user to your machine and set them up to automatically join your tmux session when they login, which we'll name "pairing."

$ gh-auth add --users="username" --command="$(which tmux) attach -s pairing"

BTW to view and remove users you can simply run:

$ gh-auth list
$ gh-auth remove --users=username

This will give them access to your normal user, you could create a new user with different privileges. I'm simply creating an alias for my user, with the username tmux.

3. Ngrok

Unless you want to setup a server for this and put your code up there, SSHing into your localhost can be a bit tricky. Ngrok is a nifty, open source project (see ngrok on gihub) that basically acts as a proxy to your machine. You can install it on a server yourself, or use

To use's service, all you have to do is, after downloading it, run this first line:

$ ./ngrok -proto=tcp 22

ngrok                                              (Ctrl+C to quit)
Tunnel Status                 online
Version                       1.6/1.5
Forwarding                    tcp:// ->
Web Interface       
# Conn                        0
Avg Conn Time                 0.00ms

That'll work for SSHing, and It'll give you a random port to connect to. Also, if for instance you had a rails server running on port 3000, you could expose it with ngrok and get a random subdomain on to connect to by running:

$ ./ngrok 3000

ngrok                                                      (Ctrl+C to quit)
Tunnel Status                 online
Version                       1.6/1.5
Forwarding           ->
Forwarding           ->
Web Interface       
# Conn                        0
Avg Conn Time                 0.00ms

Note: I've seen a number of people talk about and use Ultimately who knows what happens on his server, or his executable! Seeing that he has a number of largely followed projects, I've seen a number of big companies mention it, and all I'm really sending is bits of encrypted code back and forth, I'm going to trust him... for now.

4. Pair

Now, to set it all up, after starting ngrok, start your tmux session

$ tmux new -s pairing

And then simply have your friend connect via ssh to the ngrok server and port number ngrok gave you.

ssh -p 12345

and violà!

You can kill the tmux session with tmux kill-server, shut down ngrok with ctrl+c, and then remove the user's keys with gh-auth . Just make sure you trust the person on the other end... and re-iterate to your co-workers NOT to goof around and type something stupid... ever.

There's also wemux which you can setup read-only modes and has a few other nifty features. I may try to setup another user with restricted access.


PS Note on vim colors: I had some troubles with getting colors to work with tmux. You have to make sure tmux is using 256 colors. I have a bash alias for this:

# vim colors in tmux. c.f.
alias tmux="TERM=screen-256color-bce tmux"                                      

And then in ~/.tmux.conf

set -g default-terminal "xterm-256color"
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