What is Apple Push Notification Service
The Apple Push Notification Service is a service created by Apple Inc., it uses push technology through a constantly open IP connection to forward notifications from the servers of third party applications to the Apple devices; such notifications may include badges, sounds or custom text alerts.
As a provider, you need to communicate with the Apple Push Notification
Service (APNS) to send the messages that are then pushed to the phone.
This is necessary so that the device only needs to maintain 1 connection
to the APNS, helping to reduce battery usage.
Basic Structure
- You connect to the APNS using your unique SSL certificate
- Cycle through the messages you want to send
- Construct the payload for each message
- Disconnect from APNS
Device Token
Each push message must be “addressed” to a specific device. This is
achieved by using a unique deviceToken generated by APNS within your
iPhone application. Once this token has been retrieved, you need to
store it on your server.
Implementation
Here is a sample implementation of Apple Push Notification Service through PHP
Create apns.php
<?php
// authentication
$host = "localhost";
$user = "db_username";
$pass = "db_password";
$dbname = "db_name";
// create connection with database
$con = mysql_connect($host,$user,$pass);
// check whether database connection is successful
if (!$con) {
// if connection not successful then stop the script and show the error
die('Could not connect to database: ' . mysql_error());
} else {
// if database connection successful then select the database
mysql_select_db($dbname, $con);
}
// get the id, token from database
$result = mysql_query("SELECT id,token FROM `device_tokens` ORDER BY id");
//Setup notification message
$body = array();
$body['aps'] = array('alert' => 'This is push message');
$body['aps']['notifurl'] = 'http://www.mydomain.com';
$body['aps']['badge'] = 2;
//Setup stream (connect to Apple Push Server)
$ctx = stream_context_create();
stream_context_set_option($ctx, 'ssl', 'passphrase', 'password_for_apns.pem_file');
stream_context_set_option($ctx, 'ssl', 'local_cert', 'apns_pem_certificate.pem');
$fp = stream_socket_client('ssl://gateway.push.apple.com:2195', $err, $errstr, 60, STREAM_CLIENT_CONNECT, $ctx);
stream_set_blocking ($fp, 0);
// This allows fread() to return right away when there are no errors. But it can also miss errors during
// last seconds of sending, as there is a delay before error is returned. Workaround is to pause briefly
// AFTER sending last notification, and then do one more fread() to see if anything else is there.
if (!$fp) {
//ERROR
echo "Failed to connect (stream_socket_client): $err $errstrn";
} else {
// Keep push alive (waiting for delivery) for 90 days
$apple_expiry = time() + (90 * 24 * 60 * 60);
// Loop thru tokens from database
while($row = mysql_fetch_array($result)) {
$apple_identifier = $row["id"];
$deviceToken = $row["token"];
$payload = json_encode($body);
// Enhanced Notification
$msg = pack("C", 1) . pack("N", $apple_identifier) . pack("N", $apple_expiry) . pack("n", 32) . pack('H*', str_replace(' ', '', $deviceToken)) . pack("n", strlen($payload)) . $payload;
// SEND PUSH
fwrite($fp, $msg);
// We can check if an error has been returned while we are sending, but we also need to
// check once more after we are done sending in case there was a delay with error response.
checkAppleErrorResponse($fp);
}
// Workaround to check if there were any errors during the last seconds of sending.
// Pause for half a second.
// Note I tested this with up to a 5 minute pause, and the error message was still available to be retrieved
usleep(500000);
checkAppleErrorResponse($fp);
echo 'Completed';
mysql_close($con);
fclose($fp);
}
// FUNCTION to check if there is an error response from Apple
// Returns TRUE if there was and FALSE if there was not
function checkAppleErrorResponse($fp) {
//byte1=always 8, byte2=StatusCode, bytes3,4,5,6=identifier(rowID).
// Should return nothing if OK.
//NOTE: Make sure you set stream_set_blocking($fp, 0) or else fread will pause your script and wait
// forever when there is no response to be sent.
$apple_error_response = fread($fp, 6);
if ($apple_error_response) {
// unpack the error response (first byte 'command" should always be 8)
$error_response = unpack('Ccommand/Cstatus_code/Nidentifier', $apple_error_response);
if ($error_response['status_code'] == '0') {
$error_response['status_code'] = '0-No errors encountered';
} else if ($error_response['status_code'] == '1') {
$error_response['status_code'] = '1-Processing error';
} else if ($error_response['status_code'] == '2') {
$error_response['status_code'] = '2-Missing device token';
} else if ($error_response['status_code'] == '3') {
$error_response['status_code'] = '3-Missing topic';
} else if ($error_response['status_code'] == '4') {
$error_response['status_code'] = '4-Missing payload';
} else if ($error_response['status_code'] == '5') {
$error_response['status_code'] = '5-Invalid token size';
} else if ($error_response['status_code'] == '6') {
$error_response['status_code'] = '6-Invalid topic size';
} else if ($error_response['status_code'] == '7') {
$error_response['status_code'] = '7-Invalid payload size';
} else if ($error_response['status_code'] == '8') {
$error_response['status_code'] = '8-Invalid token';
} else if ($error_response['status_code'] == '255') {
$error_response['status_code'] = '255-None (unknown)';
} else {
$error_response['status_code'] = $error_response['status_code'].'-Not listed';
}
echo '<br><b>+ + + + + + ERROR</b> Response Command:<b>' . $error_response['command'] . '</b> Identifier:<b>' . $error_response['identifier'] . '</b> Status:<b>' . $error_response['status_code'] . '</b><br>';
echo 'Identifier is the rowID (index) in the database that caused the problem, and Apple will disconnect you from server. To continue sending Push Notifications, just start at the next rowID after this Identifier.<br>';
return true;
}
return false;
}
?>
Setup Cronjob
While you want to send huge amount of push notification, then it would be better to add to crontab.
Open crontab to add a new cronjob
$ crontab -e
Add a cronjob (Assume you want to run the cron every 5 minutes)
*/5 * * * * myuser /usr/bin/php -f /absolute/path/to/apns.php fetch > /usr/local/apns/apns.log 2>&1 &
Here, the > operator used to redirect the standard output generated by the process to a suitable location, while the & operator sends the process to the background and returns the control to the calling process.
You can discard the output by sending it to /dev/null
It is also a good practice to keep track of id of the process you execute in the background. You can retrive it via the $! operator and store it in a variable for future use.
