Linux – On Linux, how can I tell how many ephemeral ports are left available

There's no 100% accurate way really, but there's a way to give a good guess.

There is a python library chardet which is available here: https://pypi.python.org/pypi/chardet

e.g.

See what the current LANG variable is set to:

$ echo $LANG
en_IE.UTF-8

Create a filename that'll need to be encoded with UTF-8

$ touch mÉ.txt

Change our encoding and see what happens when we try and list it

$ ls m*
mÉ.txt
$ export LANG=C
$ ls m*
m??.txt

OK, so now we have a filename encoded in UTF-8 and our current locale is C (standard Unix codepage).

So start up python, import chardet and get it to read the filename. I'm use some shell globbing (i.e. expansion through the * wildcard character) to get my file. Change "ls m*" to whatever will match one of your example files.

>>> import chardet
>>> import os
>>> chardet.detect(os.popen("ls m*").read())
{'confidence': 0.505, 'encoding': 'utf-8'}

As you can see, it's only a guess. How good a guess is shown by the "confidence" variable.

Solution

Here is what I finally came up with after being set in the right direction by Miles Erickson. I wanted the address bar to reflect the original subdomain/domain of the request and not the redirected server and port, but he put me on the right path to Google up a solution using VirtualHost and I finally found a solution that included the use of mod_proxy.

First, make sure mod_proxy is enabled:

sudo a2enmod proxy
sudo a2enmod proxy_http
sudo a2enmod proxy_balancer
sudo a2enmod lbmethod_byrequests
sudo systemctl restart apache2

Next, add the following to your site config (e.g., /etc/apache2/sites-available/000-default.conf):

<VirtualHost *:80>
    ServerAdmin me@mydomain.com
    ServerName dev.mydomain.com
    ProxyPreserveHost On

    # setup the proxy
    <Proxy *>
        Order allow,deny
        Allow from all
    </Proxy>
    ProxyPass / http://localhost:8888/
    ProxyPassReverse / http://localhost:8888/
</VirtualHost>