page.title=GCM HTTP Connection Server
@jd:body

<div id="qv-wrapper">
<div id="qv">


<h2>In this document</h2>

<ol class="toc">
  <li><a href="#auth">Authentication</a> </li>
  <li><a href="#request">Request Format</a> </li>
  <li><a href="#response">Response Format</a>
  <ol class="toc">
    <li><a href="#success">Interpreting a success response</a>
    <li><a href="#error_codes">Interpreting an error response</a>
    <li><a href="#example-responses">Example responses</a>
  </ol>
  </li>
  <li><a href="#app-server">Implementing an HTTP-Based App Server</a>
</ol>

<h2>See Also</h2>

<ol class="toc">
<li><a href="server-ref.html">Server Reference</a></li>
<li><a href="gs.html">Getting Started</a></li>
<li><a href="client.html">Implementing GCM Client</a></li>
<li><a href="ccs.html">Cloud Connection Server</a></li>


</ol>

</div>
</div>

<p>This document describes the Google Cloud Messaging (GCM) HTTP
connection server. Connection servers
are the Google-provided servers that take messages from the 3rd-party
application server and sending them to the device.</p>

<p class="note"><strong>Note:</strong> The content in this document
applies to <a href="http://developer.chrome.com/apps/cloudMessaging">
GCM with Chrome apps</a> as well as Android.</p>

<p>See the
<a href="server-ref.html">Server Reference</a> for a list of all the message
parameters and which connection server(s) supports them.</p>


<h2 id="auth">Authentication</h2>

<p>To send a  message, the application server issues a POST request. For example:</p>
<pre>https://android.googleapis.com/gcm/send</pre>
<p>A  message request is made of 2 parts: HTTP header and HTTP body.</p>

<p>The HTTP header must contain the following headers:</p>
<ul>
  <li><code>Authorization</code>: key=YOUR_API_KEY</li>
  <li><code>Content-Type</code>: <code>application/json</code> for JSON;
<code>application/x-www-form-urlencoded;charset=UTF-8</code> for plain text.
If <code>Content-Type</code> is omitted, the format
is assumed to be plain text.
  </li>
</ul>

<p>For example:
</p>

<pre>Content-Type:application/json
Authorization:key=AIzaSyB-1uEai2WiUapxCs2Q0GZYzPu7Udno5aA

{
  "registration_ids" : ["APA91bHun4MxP5egoKMwt2KZFBaFUH-1RYqx..."],
  "data" : {
    ...
  },
}</pre>


<p>The HTTP body content depends on whether you're using JSON or plain text.
See
<a href="server-ref.html#params">the Server Reference</a> for a list of all the
parameters your JSON or plain text message can contain.</p>


  <h2 id="request">Request Format</h2>

<p>This section shows you how to format a request for both JSON and plain text. See
the <a href="server-ref.html#table1">Server Reference</a> for a complete
list of the fields you can include in a request.</p>

  <p>Here is the smallest possible request (a message without any parameters and
just one recipient) using JSON:</p>

  <pre class="prettyprint pretty-json">{ &quot;registration_ids&quot;: [ &quot;42&quot; ] }</pre>

  <p>And here the same example using plain text:</p>
  <pre class="prettyprint">registration_id=42</pre>

  <p> Here is a message with a payload and 6 recipients:</p>

  <pre class="prettyprint pretty-HTML">{ "data": {
    "score": "5x1",
    "time": "15:10"
  },
  "registration_ids": ["4", "8", "15", "16", "23", "42"]
}</pre>
  <p>Here is a message with all optional fields set and 6 recipients:</p>
  <pre class="prettyprint pretty-json">{ "collapse_key": "score_update",
  "time_to_live": 108,
  "delay_while_idle": true,
  "data": {
    "score": "4x8",
    "time": "15:16.2342"
  },
  "registration_ids":["4", "8", "15", "16", "23", "42"]
}</pre>
  <p>And here is the same message using plain-text format (but just 1 recipient):  </p>

  <pre class="prettyprint">collapse_key=score_update&amp;time_to_live=108&amp;delay_while_idle=1&amp;data.score=4x8&amp;data.time=15:16.2342&amp;registration_id=42
  </pre>

<p>Here is a message that includes a notification key and payload:</p>

<pre>
{
  "data": {
    "message": "ciao"
  },
  "notification_key":"aUniqueKey"
}
</pre>

<p>For more information about notifications and how to use them, see
<a href="{@docRoot}google/gcm/notifications.html">User Notifications</a>.</p>


<p class="note"><strong>Note:</strong> If your organization has a firewall
that restricts the traffic to or
from the Internet, you need to configure it to allow connectivity with GCM in order for
your GCM client apps to receive messages.
The ports to open are: 5228, 5229, and 5230. GCM typically only uses 5228, but
it sometimes uses 5229 and 5230. GCM doesn't provide specific IPs, so you should allow
your firewall to accept outgoing connections to all IP addresses
contained in the IP blocks listed in Google's ASN of 15169.</p>



<h2 id="response">Response format</h2>

<p>There are two possible outcomes when trying to send a message:</p>
<ul>
  <li>The message is processed successfully. The HTTP response has a 200 status, and
the body contains more information about the status of the message (including possible errors).</li>
  <li>The GCM server rejects the request. The HTTP response contains a
non-200 status code (such as 400, 401 or 5xx).</li>
</ul>

<h3 id="success">Interpreting a success response</h3>
<p>When a JSON request is successful (HTTP status code 200), the response body
contains a JSON object with the following fields:</p>
<table>
  <tr>
    <th>Field</th>
    <th>Description</th>
  </tr>
  <tr>
    <td><code>multicast_id</code></td>
    <td>Unique ID (number) identifying the multicast message.</td>
  </tr>
  <tr>
    <td><code>success</code></td>
    <td>Number of messages that were processed without an error.</td>
  </tr>
  <tr>
    <td><code>failure</code></td>
    <td>Number of messages that could not be processed.</td>
  </tr>
  <tr>
    <td><code>canonical_ids</code></td>
    <td>Number of results that contain a canonical registration ID. See
<a href="adv.html#canonical">Advanced Topics</a> for more discussion of this topic.</td>
  </tr>
  <tr>
    <td><code>results</code></td>
    <td>Array of objects representing the status of the messages processed. The
objects are listed in the same order as the request (i.e., for each registration
ID in the request, its result is listed in the same index in the response) and
they can have these fields:<br>
      <ul>
        <li><code>message_id</code>: String representing the message when it was
successfully processed.</li>
        <li><code>registration_id</code>: If set,  means that GCM processed the
message but it has another canonical registration ID for that device, so sender
should replace the IDs on future requests (otherwise they might be rejected).
This field is never set if there is an error in the request.
        </li>
        <li><code>error</code>: String describing an error that occurred while
processing the message for that recipient. The possible values are the same as
documented in the above table, plus &quot;Unavailable&quot;  (meaning GCM servers
were busy and could not process the message for that  particular recipient, so
it could be retried).</li>
    </ul></td>
  </tr>
</table>
<p>If the value of <code>failure</code> and <code>canonical_ids</code> is 0, it's
not necessary to parse the remainder of the response. Otherwise, we recommend
that you iterate through the results field and do the following for each object
in that list:</p>
<ul>
  <li>If <code>message_id</code> is set, check for <code>registration_id</code>:
    <ul>
      <li>If <code>registration_id</code> is set, replace the original ID with
the new value (canonical ID) in your server database. Note that the original ID
is not part of the result, so you need to obtain it from the list of
code>registration_ids</code> passed in the request (using the same index).</li>
    </ul>
  </li>
  <li>Otherwise, get the value of <code>error</code>:
    <ul>
      <li>If it is <code>Unavailable</code>, you could retry to send it in another
request.</li>
      <li>If it is <code>NotRegistered</code>, you should remove the registration
ID from your server database because the application was uninstalled from the
device, or the client app isn't configured to receive
messages.</li>
      <li>Otherwise, there is something wrong in the registration ID passed in
the request; it is probably a non-recoverable error that will also require removing
the registration from the server database. See <a href="#error_codes">Interpreting
an error response</a> for all possible error values.</li>
    </ul>
  </li>
</ul>

<p>When a plain-text request is successful (HTTP status code 200), the response
body contains 1 or 2 lines in the form of key/value pairs.
The first line is always available and its content is either <code>id=<em>ID of
sent message</em></code> or <code>Error=<em>GCM error code</em></code>. The second
line, if available,
has the format of <code>registration_id=<em>canonical ID</em></code>. The second
line is optional, and it can only be sent if the first line is not an error. We
recommend handling the plain-text response in a similar way as handling the
JSON response:</p>
<ul>
  <li>If first line starts with <code>id</code>, check second line:
    <ul>
      <li>If second line starts with <code>registration_id</code>, gets its value
and replace the registration IDs in your server database.</li>
    </ul>
  </li>
  <li>Otherwise, get the value of <code>Error</code>:
    <ul>
      <li>If it is <code>NotRegistered</code>, remove the registration ID from
your server database.</li>
      <li>Otherwise, there is probably a non-recoverable error (<strong>Note:
</strong>Plain-text requests will never return <code>Unavailable</code> as the
error code, they would have returned a 500 HTTP status instead).</li>
    </ul>
  </li>
</ul>

<h3 id="error_codes">Interpreting an error response</h3>
<p>Here are the recommendations for handling the different types of error that
might occur when trying to send a message to a device:</p>

<dl>
<dt id="missing_reg"><strong>Missing Registration ID</strong></dt>
<dd>Check that the request contains a registration ID (either in the
<code>registration_id</code> parameter in a plain text message, or in the
<code>registration_ids</code> field in JSON).
<br/>Happens when error code is <code>MissingRegistration</code>.</dd>

<dt id="invalid_reg"><strong>Invalid Registration ID</strong></dt>
<dd>Check the formatting of the registration ID that you pass to the server. Make
sure it matches the registration ID the client app receives and that you're
not truncating it or adding additional characters.
<br/>Happens when error code is <code>InvalidRegistration</code>.</dd>

<dt id="mismatched_sender"><strong>Mismatched Sender</strong></dt>
<dd>A registration ID is tied to a certain group of senders. When an application
registers for GCM usage, it must specify which senders are allowed to send messages.
Make sure you're using one of those when trying to send messages to the device.
If you switch to a different sender, the existing registration IDs won't work.
Happens when error code is <code>MismatchSenderId</code>.</dd>

<dt id="unreg_device"><strong>Unregistered Device</strong></dt>
<dd>An existing registration ID may cease to be valid in a number of scenarios, including:
<ul>
  <li>If the application manually unregisters.</li>
  <li>If the application is automatically unregistered, which can happen
(but is not guaranteed) if the user uninstalls the application.</li>
  <li>If the registration ID expires. Google might decide to refresh registration
IDs. </li>
  <li>If the application is updated but the new version is not configured to receive
messages.</li>
</ul>
For all these cases, you should remove this registration ID from the 3rd-party
server and stop using it to send
messages.
<br/>Happens when error code is <code>NotRegistered</code>.</dd>

<dt id="big_msg"><strong>Message Too Big</strong></dt>
  <dd>The total size of the payload data that is included in a message can't
exceed 4096 bytes. Note that this includes both the size of the keys as well
as the values.
<br/>Happens when error code is <code>MessageTooBig</code>.</dd>

<dt id="invalid_datakey"><strong>Invalid Data Key</strong></dt>
<dd>The payload data contains a key (such as <code>from</code> or any value
prefixed by <code>google.</code>) that is used internally by GCM and therefore cannot be used.
Note that some words (such as <code>collapse_key</code>) are also used by GCM
but are allowed in the payload, in which case the payload value will be
overridden by the GCM value.
<br />
Happens when the error code is <code>InvalidDataKey</code>.</dd>

<dt id="ttl_error"><strong>Invalid Time To Live</strong></dt>
  <dd>The value for the Time to Live field must be an integer representing
a duration in seconds between 0 and 2,419,200 (4 weeks). Happens when error code
is <code>InvalidTtl</code>.
</dd>

  <dt id="auth_error"><strong>Authentication Error</strong></dt>
  <dd>The sender account that you're trying to use to send a message couldn't be
authenticated. Possible causes are: <ul>
<li>Authorization header missing or with invalid syntax.</li>
<li>Invalid project number sent as key.</li>
<li>Key valid but with GCM service disabled.</li>
<li>Request originated from a server not whitelisted in the Server Key IPs.</li>

</ul>
When there is an Authentication Error, you can check the validity of your API key by running You can check the validity
of your API key by running the following command (this example shows what you
would do on Android; see the documentation for your platform):<br/>

<pre># api_key=YOUR_API_KEY

# curl --header "Authorization: key=$api_key" --header Content-Type:"application/json" https://android.googleapis.com/gcm/send  -d "{\"registration_ids\":[\"ABC\"]}"</pre>



If you receive a 401 HTTP status code, your API key is not valid. Otherwise you
should see something like this:<br/>

<pre>
{"multicast_id":6782339717028231855,"success":0,"failure":1,"canonical_ids":0,"results":[{"error":"InvalidRegistration"}]}
</pre>
If you want to confirm the validity of a registration ID, you can do so by
replacing "ABC" with the registration ID.
<br/>
Happens when the HTTP status code is 401.

  <dt id="timeout"><strong>Timeout</strong></dt>

<dd>The server couldn't process the request in time. You should retry the
same request, but you MUST obey the following requirements:

<ul>

<li>Honor the <code>Retry-After</code> header if it's included in the response
from the GCM server.</li>


<li>Implement exponential back-off in your retry mechanism. This means an
exponentially increasing delay after each failed retry (e.g. if you waited one
second before the first retry, wait at least two second before the next one,
then 4 seconds and so on). If you're sending multiple messages, delay each one
independently by an additional random amount to avoid issuing a new request for
all messages at the same time.</li>


Senders that cause problems risk being blacklisted.
<br />
Happens when the HTTP status code is between 501 and 599, or when the
<code>error</code> field of a JSON object in the results array is <code>Unavailable</code>.
</dd>

<dt id="internal_error"><strong>Internal Server Error</strong></dt>

<dd>
The server encountered an error while trying to process the request. You
could retry the same request (obeying the requirements listed in the <a href="#timeout">Timeout</a>
section), but if the error persists, please report the problem to Google.
<br />
Happens when the HTTP status code is 500, or when the <code>error</code> field of a JSON
object in the results array is <code>InternalServerError</code>.
</dd>

<dt id="restricted_package_name"><strong>Invalid Package Name</strong></dt>

<dd>
A message was addressed to a registration ID whose package name did not match
the value passed in the request. Happens when error code is
<code>InvalidPackageName</code>.
</dd>

<dt id="big_msg"><strong>Device Message Rate Exceeded</strong></dt>
  <dd>The rate of messages to a particular device is too high. You should reduce the number
of messages sent to this device and should not retry sending to this device immediately.
<br/>Happens when error code is <code>DeviceMessageRateExceeded</code>.</dd>

</dl>

<h3 id="example-responses">Example responses</h3>
<p>This section shows a few examples of responses indicating messages that were
processed successfully. See <a href="#request">Request Format</a> for
the requests these responses are based on.</p>
<p> Here is a simple case of a JSON message successfully sent to one recipient
without canonical IDs in the response:</p>
<pre class="prettyprint pretty-json">{ "multicast_id": 108,
  "success": 1,
  "failure": 0,
  "canonical_ids": 0,
  "results": [
    { "message_id": "1:08" }
  ]
}</pre>

<p>Or if the request was in plain-text format:</p>
<pre class="prettyprint">id=1:08
</pre>

<p>Here are JSON results for 6 recipients (IDs 4, 8, 15, 16, 23, and 42 respectively)
with 3 messages successfully processed, 1 canonical registration ID returned,
and 3 errors:</p>
<pre class="prettyprint pretty-json">{ "multicast_id": 216,
  "success": 3,
  "failure": 3,
  "canonical_ids": 1,
  "results": [
    { "message_id": "1:0408" },
    { "error": "Unavailable" },
    { "error": "InvalidRegistration" },
    { "message_id": "1:1516" },
    { "message_id": "1:2342", "registration_id": "32" },
    { "error": "NotRegistered"}
  ]
}
</pre>
<p> In this example:</p>
<ul>
  <li>First message: success, not required.</li>
  <li>Second message: should be resent (to registration ID 8).</li>
  <li>Third message: had an unrecoverable error (maybe the value got corrupted
in the database).</li>
  <li>Fourth message: success, nothing required.</li>
  <li>Fifth message: success, but the registration ID should be updated in the
server database (from 23 to 32).</li>
  <li>Sixth message: registration ID (42) should be removed from the server database
because the application was uninstalled from the device.</li>
</ul>
<p>Or if just the 4th message above was sent using plain-text format:</p>
<pre class="prettyprint">Error=InvalidRegistration
</pre>
<p>If the 5th message above was also sent using plain-text format:</p>
<pre class="prettyprint">id=1:2342
registration_id=32
</pre>


<h2 id="app-server">Implementing an HTTP-Based App Server</h2>

<p>This section gives examples of implementing an app server that works with the
GCM HTTP connection server. Note that a full GCM implementation requires a
client-side implementation, in addition to the server. This example is based on Android.</a>


<p>Requirements</p>
<p>For the web server:</p>
<ul>
  <li> <a href="http://ant.apache.org/">Ant 1.8</a> (it might work with earlier versions, but it's not guaranteed).</li>
  <li>One of the following:
    <ul>
      <li>A running web server compatible with Servlets API version 2.5, such as
<a href="http://tomcat.apache.org/">Tomcat 6</a> or <a href="http://jetty.codehaus.org/">Jetty</a>, or</li>
      <li><a href="http://code.google.com/appengine/">Java App Engine SDK</a>
version 1.6 or later.</li>
    </ul>
  </li>
  <li>A Google account registered to use GCM.</li>
  <li>The API  key for that account.</li>
</ul>
<p>For the Android application:</p>
<ul>
  <li>Emulator (or device) running Android 2.2 (ideally, 2.3 or above) with Google APIs.</li>
  <li>The Google API project number of the account registered to use GCM.</li>
</ul>

<h3 id="gcm-setup">Setting Up GCM</h3>
<p>Before proceeding with the server and client setup, it's necessary to register
a Google account with the Google API Console, enable Google Cloud Messaging in GCM,
and obtain an API key from the <a href="https://code.google.com/apis/console">
Google API Console</a>.</p>
<p>For instructions on how to set up GCM, see <a href="gs.html">Getting Started</a>.</p>


<h3 id="server-setup">Setting Up an HTTP Server</h3>
<p>This section describes the different options for setting up an HTTP server.</p>

<h4 id="webserver-setup">Using a standard web server</h4>
<p>To set up the server using a standard, servlet-compliant web server:</p>
<ol>
  <li>From the <a href="http://code.google.com/p/gcm">open source site</a>,
download the following directories: <code>gcm-server</code>,
<code>samples/gcm-demo-server</code>, and <code>samples/gcm-demo-appengine</code>.</p>


  <li>In a text editor, edit the <code>samples/gcm-demo-server/WebContent/WEB-INF/classes/api.key</code> and replace the existing text with the API key obtained above.</li>
  <li>In a shell window, go to the <code>samples/gcm-demo-server</code> directory.</li>
  <li>Generate the server's WAR file by running <code>ant war</code>:</li>

  <pre class="prettyprint">$ ant war

Buildfile:build.xml

init:
   [mkdir] Created dir: build/classes
   [mkdir] Created dir: dist

compile:
   [javac] Compiling 6 source files to build/classes

war:
     [war] Building war: <strong>dist/gcm-demo.war</strong>

BUILD SUCCESSFUL
Total time: 0 seconds
</pre>

  <li>Deploy the <code>dist/gcm-demo.war</code> to your running server. For instance, if you're using Jetty, copy <code>gcm-demo.war</code> to the <code>webapps</code> directory of the Jetty installation.</li>
  <li>Open the server's main page in a browser. The URL depends on the server you're using and your machine's IP address, but it will be something like <code>http://192.168.1.10:8080/gcm-demo/home</code>, where <code>gcm-demo</code> is the application context and <code>/home</code> is the path of the main servlet.

  </li>
</ol>
<p class="note"><strong>Note:</strong> You can get the IP by running <code>ifconfig</code> on Linux or MacOS, or <code>ipconfig</code> on Windows. </p>

<p> You server is now ready.</p>

<h4 id="appengine-setup">Using App Engine for Java</h4>

<p>To set up the server using a standard App Engine for Java:</p>
<ol>
  <li>Get the files from the <a href="http://code.google.com/p/gcm">open source
site</a>, as described above.</p>
  </li>
  <li>In a text editor, edit
<code>samples/gcm-demo-appengine/src/com/google/android/gcm/demo/server/ApiKeyInitializer.java</code>
and replace the existing text with the API key obtained above.

  <p class="note"><strong>Note:</strong> The API key value set in that class will
be used just once to create a persistent entity on App Engine. If you deploy
the application, you can use App Engine's <code>Datastore Viewer</code> to change
it later.</p>

  </li>
  <li>In a shell window, go to the <code>samples/gcm-demo-appengine</code> directory.</li>
  <li>Start the development App Engine server by <code>ant runserver</code>,
using the <code>-Dsdk.dir</code> to indicate the location of the App Engine SDK
and <code>-Dserver.host</code> to set your server's hostname or IP address:</li>

<pre class="prettyprint">
$ ant -Dsdk.dir=/opt/google/appengine-java-sdk runserver -Dserver.host=192.168.1.10
Buildfile: gcm-demo-appengine/build.xml

init:
    [mkdir] Created dir: gcm-demo-appengine/dist

copyjars:

compile:

datanucleusenhance:
  [enhance] DataNucleus Enhancer (version 1.1.4) : Enhancement of classes
  [enhance] DataNucleus Enhancer completed with success for 0 classes. Timings : input=28 ms, enhance=0 ms, total=28 ms. Consult the log for full details
  [enhance] DataNucleus Enhancer completed and no classes were enhanced. Consult the log for full details

runserver:
     [java] Jun 15, 2012 8:46:06 PM com.google.apphosting.utils.jetty.JettyLogger info
     [java] INFO: Logging to JettyLogger(null) via com.google.apphosting.utils.jetty.JettyLogger
     [java] Jun 15, 2012 8:46:06 PM com.google.apphosting.utils.config.AppEngineWebXmlReader readAppEngineWebXml
     [java] INFO: Successfully processed gcm-demo-appengine/WebContent/WEB-INF/appengine-web.xml
     [java] Jun 15, 2012 8:46:06 PM com.google.apphosting.utils.config.AbstractConfigXmlReader readConfigXml
     [java] INFO: Successfully processed gcm-demo-appengine/WebContent/WEB-INF/web.xml
     [java] Jun 15, 2012 8:46:09 PM com.google.android.gcm.demo.server.ApiKeyInitializer contextInitialized
     [java] SEVERE: Created fake key. Please go to App Engine admin console, change its value to your API Key (the entity type is 'Settings' and its field to be changed is 'ApiKey'), then restart the server!
     [java] Jun 15, 2012 8:46:09 PM com.google.appengine.tools.development.DevAppServerImpl start
     [java] INFO: The server is running at http://192.168.1.10:8080/
     [java] Jun 15, 2012 8:46:09 PM com.google.appengine.tools.development.DevAppServerImpl start
     [java] INFO: The admin console is running at http://192.168.1.10:8080/_ah/admin
</pre>

  <li>Open the server's main page in a browser. The URL depends on the server
you're using and your machine's IP address, but it will be something like
<code>http://192.168.1.10:8080/home</code>, where <code>/home</code>
is the path of the main servlet.</li>

  <p class="note"><strong>Note:</strong> You can get the IP by running <code>ifconfig</code>
on Linux or MacOS, or <code>ipconfig</code> on Windows.</p>

</ol>
<p> You server is now ready.</p>