Does anyone know how to write an Apple Push Notification Provider in C#?

Question

Apple really has bad documentation about how the provider connects and communicates to their service. I am confused about the protocol. If anyone out there could provide a C# sample of how this is don, it would be greatly appreciated.

Answer 1

I hope this is relevant (slightly), but I have just successfully created one for Java, so conceptually quite similar to C# (except perhaps the SSL stuff, but that shouldn't be too hard to modify. Below is a sample message payload and crypto setup:

    int port = 2195;
    String hostname = "gateway.sandbox.push.apple.com";


    char []passwKey = "<keystorePassword>".toCharArray();
    KeyStore ts = KeyStore.getInstance("PKCS12");
    ts.load(new FileInputStream("/path/to/apn_keystore/cert.p12"), passwKey);

    KeyManagerFactory tmf = KeyManagerFactory.getInstance("SunX509");
    tmf.init(ts,passwKey);
    SSLContext sslContext = SSLContext.getInstance("TLS");
    sslContext.init(tmf.getKeyManagers(), null, null);
    SSLSocketFactory factory =sslContext.getSocketFactory();
    SSLSocket socket = (SSLSocket) factory.createSocket(hostname,port); // Create the ServerSocket
    String[] suites = socket.getSupportedCipherSuites();
    socket.setEnabledCipherSuites(suites);
    //start handshake

    socket.startHandshake();


    // Create streams to securely send and receive data to the server
    InputStream in = socket.getInputStream();
    OutputStream out = socket.getOutputStream();



    // Read from in and write to out...
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    baos.write(0); //The command
    System.out.println("First byte Current size: " + baos.size());

    baos.write(0); //The first byte of the deviceId length    
    baos.write(32); //The deviceId length

    System.out.println("Second byte Current size: " + baos.size());

    String deviceId = "<heaxdecimal representation of deviceId";
    baos.write(hexStringToByteArray(deviceId.toUpperCase()));
    System.out.println("Device ID: Current size: " + baos.size());


    String payload = "{\"aps\":{\"alert\":\"I like spoons also\",\"badge\":14}}";
    System.out.println("Sending payload: " + payload);
    baos.write(0); //First byte of payload length;
    baos.write(payload.length());
    baos.write(payload.getBytes());

    out.write(baos.toByteArray());
    out.flush();

    System.out.println("Closing socket..");
    // Close the socket
    in.close();
    out.close();

}

Once again, not C#, but at least closer than the poor ObjC sample that Apple provides.

Answer 2

Working code example:

 int port = 2195;
 String hostname = "gateway.sandbox.push.apple.com";

 //load certificate
 string certificatePath = @"cert.p12";
 string certificatePassword = "";
 X509Certificate2 clientCertificate = new X509Certificate2(certificatePath, certificatePassword);
 X509Certificate2Collection certificatesCollection = new X509Certificate2Collection(clientCertificate);

 TcpClient client = new TcpClient(hostname, port);
 SslStream sslStream = new SslStream(
   client.GetStream(),
   false,
   new RemoteCertificateValidationCallback(ValidateServerCertificate),
   null
 );

 try
 {
  sslStream.AuthenticateAsClient(hostname, certificatesCollection, SslProtocols.Tls, true);
 }
 catch (AuthenticationException ex)
 {
  client.Close();
  return;
 }

 // Encode a test message into a byte array.
 MemoryStream memoryStream = new MemoryStream();
 BinaryWriter writer = new BinaryWriter(memoryStream);

 writer.Write((byte)0); //The command
 writer.Write((byte)0); //The first byte of the deviceId length (big-endian first byte)
 writer.Write((byte)32); //The deviceId length (big-endian second byte)

 String deviceId = "DEVICEIDGOESHERE";
 writer.Write(ToByteArray(deviceId.ToUpper()));

 String payload = "{\"aps\":{\"alert\":\"I like spoons also\",\"badge\":14}}";

 writer.Write((byte)0); //First byte of payload length; (big-endian first byte)
 writer.Write((byte)payload.Length); //payload length (big-endian second byte)

 byte[] b1 = System.Text.Encoding.UTF8.GetBytes(payload);
 writer.Write(b1);
 writer.Flush();

 byte[] array = memoryStream.ToArray();
 sslStream.Write(array);
 sslStream.Flush();

 // Close the client connection.
 client.Close();
}

Answer 3

http://code.google.com/p/apns-sharp/

Answer 4

Hi Shader,

I am using the same code as your's excpet that on the call to the sslStream.AuthenticateAsClient method, I get the following exception:

The credentials supplied to the package were not recognized

Any thoughts?

Thanks, Anthony

Answer 5

Hi there Phobis, Shader, and Chaos!

This posting is great (thank you Phobis for asking)! I am also trying to write an APNS in Java.

Have some questions:

(1) Is this approach viable to plug-in into a RESTful Web Service (say Jersey)?

(2) How does one create / register the cert.p12 and obtain the keystorePassword (is it done using XCode)?

(3) Why are there angle brackets in the ?

(4) Shader: Can you please post the hexStringToByteArray() method? I am just curious to see how it was set up.

This is what I've come up with:

public static byte[] hexStringToByteArray(String hexString) {

byte[] b = new byte[hexString.length() / 2];
for (int i = 0; i < b.length; i++) {
    int index = i * 2; 
    int v = Integer.parseInt(hexString.substring(index, index + 2), 16);
    b[i] = (byte) v;
 }
 return b;

}

(5) As one might have noticed, I had trouble formatting code in this post... Any tips?

Would really appreciate it if someone could help me with these questions or point me in the right direction...

How can I send people private messages on StackOverflow? Is there a way to send e-mails as well?

Happy programming,

Mike

Answer 6

Hi Phobis, I am having same problem as yours. I have also registered my app and using sandbox. Using sandbox environment, there will be a virtual device. then how can we connect a phone and check?

As Chaos said, how to check the notification which i am is correct? - dsk