How to use internet proxy with messages sdk

[drelephant]

We're running in a corporate network behind a proxy.

I'm trying to test the messagemedia API.

Using the first example for sending an SMS, I get the following:

failure
com.messagemedia.messages.exceptions.APIException: Failed to connect to api.messagemedia.com/54.153.174.199:443`

I tried adding these lines to the example (ip's/port redacted) :

System.setProperty("http.proxyHost", "xx.xx.xx.xxx");
System.setProperty("http.proxyPort", "xxxx");
System.setProperty("https.proxyHost", "xx.xx.xx.xxx");
System.setProperty("https.proxyPort", "xxxx");

, which worked for the following example to show an https page

package org.example;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;

public class testNetworkConnection {
    public static void main(String args[]) {
        System.setProperty("http.proxyHost", "xx.xx.xx.xxx");
        System.setProperty("http.proxyPort", "xxxx");
        System.setProperty("https.proxyHost", "xx.xx.xx.xxx");
        System.setProperty("https.proxyPort", "xxxx");
        try {
            download("https://www.google.com");
        } catch (IOException e) {
            System.out.println(e);
        }
    }
    public static void download(String urlString) throws IOException {
        URL url = new URL(urlString);
        try(
                BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream()));
        ) {
            String line;
            while ((line = reader.readLine()) != null) {
                System.out.println(line);
            }
        }
    }
}

, but it still gives the same error.

I'm not 100% sure our proxy isn't blocking the connection, but I think it isn't?

Any ideas on how to get it to connect?