How do I use Proximo as a SOCKS proxy in Java?

Question

I've got a Java app that runs on Heroku that needs to access Salesforce, which only allows API access from IPs that you whitelist. Proximo is a Heroku add-on that allows you to proxy all of the requests your app makes through a single server with a static IP. Unfortunately, the standard way of doing this—running your app within Proximo's wrapper—mucks up the creating of a listening socket for my app's webserver, as it seems to for a number of folks.

How can I use Proximo as a SOCKS proxy in my Java application?

Answer 1

I looked that stacklet that they distribute as the aforementioned wrapper and saw that it connects to the Proximo server as a SOCKS proxy. That's easy to do in Java, so I added this to the startup of my app (Groovy syntax):

URL proximo = new URL(System.getenv('PROXIMO_URL')
String userInfo = proximo.getUserInfo()
String user = userInfo.substring(0, userInfo.indexOf(':'))
String password = userInfo.substring(userInfo.indexOf(':') + 1)
System.setProperty('socksProxyHost', proximo.getHost())
System.setProperty('socksProxyPort', '1080')
Authenticator.setDefault(new ProxyAuth(user, password))

With that ProxyAuth being an inner class elsewhere:

private class ProxyAuth extends Authenticator {
    private PasswordAuthentication passwordAuthentication;

    private ProxyAuth(String user, String password) {
        passwordAuthentication = new PasswordAuthentication(user, password.toCharArray())
    }

    @Override
    protected PasswordAuthentication getPasswordAuthentication() {
        return passwordAuthentication;
    }
}