do-it-yourself ngrok alternative

December 12, 2019

if you:

• have a home server / vps
• use traefik
• use ngrok
• don’t like spending money on ngrok for memorable subdomains

you can create your own

step 1, the server

setup your traefik 1.x frontends/backends. in my case, I wanted t-1.my.domain and t-2.my.domain. two always available endpoints for whatever machine to connect to, which will be routed to a service running on my laptop.
of course you could extend this config to as many tunnels as you like

# traefik.toml

[file]
[backends]
  [backends.t-1]
    [backends.t-1.servers.t-1]
    url = "http://localhost:51401"
  [backends.t-2]
    [backends.t-2.servers.t-2]
    url = "http://localhost:51402"
[frontends]
  [frontends.t-1]
  backend = "t-1"
  passHostHeader = true
    [frontends.t-1.routes.t-1]
    rule = "Host:t-1.my.domain
  [frontends.t-2]
  backend = "t-2"
  passHostHeader = true
    [frontends.t-2.routes.t-2]
    rule = "Host:t-2.my.domain"

• for the frontends, I picked a high enough local ports that they hopefully won’t clash with any other service running on the server
• I’m also doing a passHostHeader = true for each backend, so that the request headers for the local proxied-to services have the public frontend hosts instead of localhost
• to make the public t-*.my.domain possible for my home server, I’ve got DNS similar to:

  A      my.domain    <home_ip>
  CNAME  *.my.domain  my.domain
  

  and a DDNS client updating the A record, and 80/443 forwarded

• acme should be configured, giving you TLS for a proper ngrok alternative

step 2, the client

it’s as simple as

ssh -N -R '<traefik_backend_port>:localhost:<local_service_port>' <your_box>

for every tunnel you want to create. no need for any extra binaries like with ngrok

• the -N means don’t run any remote commands, so you won’t get a shell on box. ssh will just keep the tunnel open without printing until you kill it
• the -R is key. connections to the given port on the remote host (<traefik_backend_port>) are to be forwarded to the local side (localhost:<local_service_port>

so in my case, if I want to show a friend a web server I have running at http://localhost:5454 by the more friendly and secure address https://t-1.my.domain, it would be:

ssh -N -R '51401:localhost:5454' my-box

where 51401 matches the frontend in the traefik.toml

much better :)