Alias a domain to a local port (Mac)

README.md

I run a lot of web servers for different projects, all of them on different ports. Generally I start with port 8000 and increment from there as I spin up new servers, but it became tiresome to remember what projects were running on which ports and what the next available port was.

/etc/hosts won't let you specify a port, but a combination of aliasing 127.0.0.1 to 127.0.0.X, forwarding ports from 8000 to 80, and adding the 127.0.0.X IP under an alias in /etc/hosts did work.

This script finds the next available value of X, aliases it with ifconfig, forwards the given port to port 80 with ipfw, and adds a new entry to /etc/hosts that aliases the IP to the domain you want.

Now I can add a server alias with sudo domain-alias funproject 8000, run the web server at 127.0.0.X:8000, and load up http://funproject/ in my browser.

(Because I needed it to work on a Mac, I couldn't use iptables. pfctl seems to work.)

I've written more about this on Atomic Object's blog Spin.

domain-alias.sh

#!/bin/bash

# Usage: sudo domain-alias.sh myapp 8000
domain=$1
port=$2

if [ -z "$domain" ] || [ -z "$port" ]; then
  echo "Usage: domain-alias.sh <domain> <port>"
  exit 1
fi

existing=$(cat /etc/hosts | grep $domain | cut -d' ' -f1)
if [ -n "$existing" ]; then
  localip=$existing
else
  last=$(cat /etc/hosts | grep -oE "127.0.0.\d" | cut -d'.' -f4 | sort -n | tail -1)
  next=$(expr $last + 1)
  localip="127.0.0.$next"
fi

{
  ifconfig lo0 alias $localip
  echo "rdr pass on lo0 inet proto tcp from any to $localip port 80 -> $localip port $port" | pfctl -ef -
  echo "$localip $domain" >> /etc/hosts
} && echo "Done. Run apps at $localip port $port and view them at http://$domain/."

Thanks a lot very useful !

Can you please write this command for MAC yosemite as ipfw command is not supported there

Can you please write this command for MAC yosemite as ipfw command is not supported there

Kindly pinging @exupero

Based on this comment, I was able to add localhost port forwarding using this command:

echo 'rdr pass on lo0 inet proto tcp from any to 127.0.0.1 port 8888 -> 127.0.0.1 port 8286' | sudo pfctl -ef -

(where localhost:8888 is the port to open in the browser and localhost:8286 is the port to load content from)

I'll see if I can update the script this week.