title: GCM push sender / server limit of 100
body: <p>I have my push notifications working fine for my mobile Android app
  through GCM, but have a specific question about my environment. My 
  app would like to be able to receive pushes potentially from more than 100
  senders (servers) and the comments (see below) in the documentation confuse me.</p>
  
  <p>Basically consider this situation...</p>
  
  <ul>
  <li><p>I registered my project on the Google Dev Console and obtained my 
  project number (aka - sender ID) and my server key. For the latter
  I did NOT specify specific IP addrs.. just left the field blank.</p></li>
  <li><p>My app boots and does a "register" with this one single sender ID
  and receives the registration key.</p></li>
  <li><p>I send this registration key to my 500 "source" servers, and these servers also 
  have the SAME server key.</p></li>
  </ul>
  
  <p>So again to summarize... my 500 servers that want to send pushes to the phone would 
  ALL be using the SAME server key and the SAME registration ID. </p>
  
  <p>Simple question.. is this allowed? If so, what do all the restriction warnings mean 
  (below) from the GCM docs.... and if not allowed, I want to understand technically 
  why this is not allowed.. for example, does the GCM server monitor and keep 
  track of server keys and the source IP they are from?</p>
  
  <p>Thanks so much - been searching for days and cannot get a real hard answer 
  I feel I can trust. My whole development project design hinges on the truth in 
  this matter - ha ha !</p>
  
  <hr>
  
  <p>Receiving Messages from Multiple Senders</p>
  
  <pre><code>   "GCM allows multiple parties to send messages to the same application. For example, 
      suppose your application is an articles aggregator with multiple contributors, and 
      you want each of them to be able to send a message when they publish a new article. 
      This message might contain a URL so that the application can download the article. 
      Instead of having to centralize all sending activity in one location, GCM gives you 
      the ability to let each of these contributors send its own messages.
  
      To make this possible, all you need to do is have each sender generate its own project 
      number. Then include those IDs in the sender field, separated by commas, when requesting 
      a registration. Finally, share the registration token with your partners, and they'll 
      be able to send messages to your application using their own authentication keys.
  
      Note that there is limit of 100 multiple senders."
  </code></pre>
  
  <p>or worded another way in some other doc ....</p>
  
  <p>Receiving Messages from Multi-senders</p>
  
  <pre><code>   "GCM allows multiple parties to send messages to the same client app. For example, 
      suppose the client app is an articles aggregator with multiple contributors, and 
      each of them should be able to send a message when they publish a new article. This 
      message might contain a URL so that the client app can download the article. Instead 
      of having to centralize all sending activity in one location, GCM gives you the ability 
      to let each of these contributors send its own messages.
  
      To make this possible, make sure each sender generates its own sender ID. See the 
      client documentation for your platform for information on on how to obtain the GCM 
      sender ID. When requesting registration, the client app fetches the token multiple 
      times, each time with a different sender ID in audience field.
  
      Finally, share the registration token with the corresponding app servers (to 
      complete the GCM registration client/server handshake), and they'll be able to 
      send messages to the client app using their own authentication keys.
  
      Note that there is limit of 100 multiple senders."
  </code></pre>
  
  <p>and even in some register code I saw.....</p>
  
  <pre><code>    chrome.runtime.onStartup.addListener(function() {
        chrome.storage.local.get("registered", function(result) {
          // If already registered, bail out.
          if (result["registered"])
            return;
  
          // Up to 100 senders are allowed.
          var senderIds = ["Your-Sender-ID"];
          chrome.gcm.register(senderIds, registerCallback);
        });
      });
  </code></pre>