How can I pass a notification to multiple users with GCM? - google-cloud-messaging

Question

I am trying :
private void GcmPushNotification(string deviceId)
{
string message="New post from Admin";
string GoogleAppID = "AIzaSyCYesJ5dCK8-O-tf8ZxADELQx5e05P-l5I";
var SENDER_ID = "854837747831";
var value = message;
WebRequest tRequest;
tRequest = WebRequest.Create("https://android.googleapis.com/gcm/send");
tRequest.Method = "post";
// --- text
tRequest.ContentType = " application/x-www-form-urlencoded;charset=UTF-8";
string postData = "collapse_key=score_update&time_to_live=108&delay_while_idle=1&data.message="
+ value + "&data.time=" + System.DateTime.Now.ToString() + "&registration_id=" + deviceId + "";
tRequest.Headers.Add(string.Format("Authorization: key={0}", GoogleAppID));
Console.WriteLine(postData);
Byte[] byteArray = Encoding.UTF8.GetBytes(postData);
tRequest.ContentLength = byteArray.Length;
Stream dataStream = tRequest.GetRequestStream();
dataStream.Write(byteArray, 0, byteArray.Length);
dataStream.Close();
WebResponse tResponse = tRequest.GetResponse();
dataStream = tResponse.GetResponseStream();
StreamReader tReader = new StreamReader(dataStream);
String sResponseFromServer = tReader.ReadToEnd();
tReader.Close();
dataStream.Close();
tResponse.Close();
}

Answer 1

If you want to send the same notification to multiple devices (up to 1000 registration IDs), you have to use the JSON request format instead of the URL encoded you are currently using.
For example (taken from here):
Content-Type:application/json
Authorization:key=AIzaSyB-1uEai2WiUapxCs2Q0GZYzPu7Udno5aA
{
"registration_ids" : ["APA91bHun4MxP5egoKMwt2KZFBaFUH-1RYqx..."],
"data" : {
...
},
}