Post to GoogleCloudMessaging returns 400 InvalidTokenFormat

Question

I'm trying to post to Googles Cloud Messaging Api (GCM), but my request fails with response HTTP/1.1 400 InvalidTokenFormat.

However, if I change my program so that it connects to localhost instead, and I simply pipe the request it makes through to something else that transmits the request to GCM, the request succeeds. Below is the code that fails:

import java.net.URL;
import java.net.HttpURLConnection;
import java.io.OutputStream;

public class GcmPostMe {
    public static void main (String[] args) {

        String data = "{\"to\":\" *** censored recipient token *** \"}";
        String type = "application/json";
        try {
            URL u = new URL("https://android.googleapis.com/gcm/send/");
            HttpURLConnection conn = (HttpURLConnection) u.openConnection();
            conn.setDoOutput(true);
            conn.setRequestMethod("POST");
            conn.setRequestProperty( "Authorization", "key=" + " *** censored api key *** " );
            conn.setRequestProperty( "Content-Type", type );
            conn.setRequestProperty( "Content-Length", String.valueOf(data.length()));
            OutputStream os = conn.getOutputStream();
            os.write(data.getBytes());
            System.out.println(conn.getResponseCode() + " " + conn.getResponseMessage() );
            conn.disconnect();
        } catch (Exception e) {
            System.err.println("Something went wrong");
        }
    }
}

It works when I change the URL in the code above to "http://localhost:10000/gcm/send" and do

nc -l 10000 | sed -e "s/localhost:10000/android.googleapis.com/" | openssl s_client -connect android.googleapis.com:443

before I run the program.

Answer 1

Ok, I've found my mistake: the path was wrong, the trailing / in the path somehow makes it not work.

Doing HTTP POST to https://android.googleapis.com/gcm/send/ gives you HTTP/1.1 400 InvalidTokenFormat

Doing the same POST to http://android.googleapis.com/gcm/send (without the trailing /) succeeds with HTTP/1.1 200 OK

The following works:

import java.net.URL;
import java.net.HttpURLConnection;
import java.io.OutputStream;

public class GcmPostMe {
    public static void main (String[] args) {

        String data = "{\"to\":\" *** censored recipient token *** \"}";
        String type = "application/json";
        try {
            URL u = new URL("https://android.googleapis.com/gcm/send");
            HttpURLConnection conn = (HttpURLConnection) u.openConnection();
            conn.setDoOutput(true);
            conn.setRequestMethod("POST");
            conn.setRequestProperty( "Authorization", "key=" + " *** censored api key *** " );
            conn.setRequestProperty( "Content-Type", type );
            conn.setRequestProperty( "Content-Length", String.valueOf(data.length()));
            OutputStream os = conn.getOutputStream();
            os.write(data.getBytes());
            System.out.println(conn.getResponseCode() + " " + conn.getResponseMessage() );
            conn.disconnect();
        } catch (Exception e) {
            System.err.println("Something went wrong");
        }
    }
}