Server side GCM returns error 400

Question

I am tring to implement GCM. I wrote a test code to understand how it works, but I keep getting error 400 in the response.

I\'m writing in Java (JDK 7).

I follow

Answer 1

The problem was in DataOutputStream.writeChars() and DataOutputStream.writeUTF().

Thanks to the link given by @Koh, I changed the write command in the post function to:

wr.write(json.getBytes("UTF-8"));

Now the message is being sent successfully!