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Expose local servers to the internet

2025/02/25 backup in case of serveo.net is down.

No installation, no signup. For help using Serveo, use the Serveo Google Group.

$ ssh -R 80:localhost:3000 serveo.net
# Try it! Copy and paste this into your terminal.

How does it work?

Serveo is an SSH server just for remote port forwarding. When a user connects to Serveo, they get a public URL that anybody can use to connect to their localhost server.

Manual

Basic use

$ ssh -R 80:localhost:3000 serveo.net

The -R option instructs your SSH client to request port forwarding from the server and proxy requests to the specified host and port (usually localhost). A subdomain of serveo.net will be assigned to forward HTTP traffic.

Request multiple tunnels at once

$ ssh -R 80:localhost:8888 -R 80:localhost:9999 serveo.net

The target server doesn't have to be on localhost

$ ssh -R 80:example.com:80 serveo.net

Request a particular subdomain

The subdomain is chosen deterministically based on your IP address, the provided SSH username, and subdomain availability, so you'll often get the same subdomain between restarts. You can also request a particular subdomain:

$ ssh -R incubo:80:localhost:8888 serveo.net
$ ssh -R incubo.serveo.net:80:localhost:8888 serveo.net

Change the SSH username to get assigned a different subdomain:

$ ssh -R 80:localhost:8888 foo@serveo.net
$ ssh -R 80:localhost:8888 -l foo serveo.net

Private TCP and SSH forwarding

Serveo can be used to route private TCP traffic, almost like a lightweight VPN. To set up the tunnel, specify an alias as the hostname and some port:

$ ssh -R myalias:5901:localhost:5900 serveo.net

Then to connect to that port from another machine, use ssh -L:

$ ssh -L 5902:myalias:5901 serveo.net

Then connect to localhost:5902 on the remote machine, and SSH will send traffic through Serveo, which will forward it to the target machine, ultimately connecting you to port 5900 on the target machine.

If you're using this to connect to an SSH server, then you can use OpenSSH's JumpHost feature. On the target machine, you might start the tunnel like this:

$ ssh -R myalias:22:localhost:22 serveo.net

Then you can establish an SSH connection using serveo.net as an intermediary like this:

$ ssh -J serveo.net user@myalias

The -J option was introduced in the OpenSSH client version 7.3. If you have an older client, you can use the ProxyCommand option instead:

$ ssh -o ProxyCommand="ssh -W myalias:22 serveo.net" user@myalias

Public TCP forwarding

If you request a port other than 80 or 443, raw TCP traffic will be forwarded. (In this case, there's no way to route connections based on hostname, and the host, if specified, will trigger private TCP forwarding.)

$ ssh -R 1492:localhost:1492 serveo.net

If port 0 is requested, a random TCP port will be forwarded:

$ ssh -R 0:localhost:1492 serveo.net

Connect on port 443

In some environments, outbound port 22 connections are blocked. For this reason, you can also connect on port 443.

$ ssh -p 443 -R 80:localhost:8888 serveo.net

Automatically reconnect

Use autossh for more persistent tunnels. Use -M 0 to disable autossh's connectivity checking:

$ autossh -M 0 -R 80:localhost:8888 serveo.net

See https://www.everythingcli.org/ssh-tunnelling-for-fun-and-profit-autossh/ for more about autossh.

Custom Domain

To use your own domain or subdomain, you'll first need an SSH key pair. Use the ssh-keygen program to generate a key pair if you don't already have one.

Next, use ssh-keygen -l and note your key's fingerprint. Here's an example output:

2048 SHA256:pmc7ZRv7ymCmghUwHoJWEm5ToSTd33ryeDeps5RnfRY no comment (RSA)

In this example, the fingerprint is SHA256:pmc7ZRv7ymCmghUwHoJWEm5ToSTd33ryeDeps5RnfRY.

Now you need to add two DNS records for the domain or subdomain you'd like to use:

  1. A CNAME record pointing to serveo.net.
  2. For each SSH key to allow, a TXT record at _serveo-authkey.[domain] = [fingerprint].
  3. Once your DNS records are in place, you can request your subdomain/domain from Serveo:
$ ssh -R subdomain.example.com:80:localhost:3000 serveo.net

When you request port forwarding for subdomain.example.com, Serveo will fetch the TXT records from your DNS server and only allow forwarding if you've provided a public key with the same fingerprint as specified in TXT records.

Alternatives

ngrok

Serveo is an excellent alternative to ngrok. Serveo was inspired by ngrok and attempts to serve many of the same purposes. The primary advantage of Serveo over ngrok is the use of your existing SSH client, so there's no client application to install.

Other slight advantages include preservation of URLs across reconnect for free (ngrok allows this only for paid accounts) and in-terminal request inspection and replay (ngrok uses a web interface).

OpenSSH Server

Using Serveo instead of OpenSSH frees you from having to configure and maintain a server. It also handles HTTPS and subdomain generation, two features that complicate a typical SSH port-forwarding setup.

If Serveo doesn't meet your needs, this guide has some ideas for setting up OpenSSH.