The PushRegistry maintains a list of inbound
connections. An application can register the inbound
connections with an entry in the application descriptor file
or dynamically by calling the
registerConnection method.
While an application is running, it is responsible for
all I/O operations associated with the inbound connection.
When the application is not running, the application
management software(AMS) listens for inbound notification
requests. When a notification arrives for a registered
MIDlet, the AMS will start the MIDlet
via the normal invocation of MIDlet.startApp
method.
Installation Handling of Declared Connections
To avoid collisions on inbound generic connections, the application
descriptor file MUST include information about static connections
that are needed by the MIDlet suite.
If all the static Push declarations in the application descriptor
can not be fulfilled during the installation, the user MUST be
notified that there are conflicts and the MIDlet suite MUST NOT be
installed. (See Over The Air User Initiated Provisioning
Specification section for errors reported in the event
of conflicts.)
Conditions
when the declarations can not be fulfilled include: syntax errors in
the Push attributes, declaration for a connection end point (e.g. port
number) that is already reserved in the device, declaration for a
protocol that is not supported for Push in the device, and declaration
referencing a MIDlet class that is not listed in
the MIDlet-<n> attributes of the same
application descriptor.
If the MIDlet suite
can function meaningfully even if a Push registration can't be
fulfilled, it MUST register the Push connections using the dynamic
registration methods in the PushRegistry.
A conflict-free installation reserves each requested connection for
the exclusive use of the
MIDlets in the suite. While the suite is
installed, any attempt by other applications to open one of the
reserved connections will fail with an
IOException. A call from a
MIDlet to
Connector.open()
on a connection reserved for its suite will always
succeed, assuming the suite does not already have the connection open.
If two MIDlet suites have a static push connection in
common, they cannot be installed together and both function
correctly. The end user would typically have to uninstall one before
being able to successfully install the other.
Push Registration Attribute
Each push registration entry contains the following information :
MIDlet-Push-<n>: <ConnectionURL>,
<MIDletClassName>, <AllowedSender>
-
MIDlet-Push-<n> =
the Push registration attribute name. Multiple push
registrations can be provided in a MIDlet
suite. The numeric value for <n> starts from 1 and
MUST use consecutive ordinal numbers for additional entries.
The first missing entry terminates the list. Any
additional entries are ignored.
ConnectionURL =
the connection string used in Connector.open()MIDletClassName =
the MIDlet that is responsible for the connection.
The named MIDlet MUST be registered in the
descriptor file or the jar file manifest with a
MIDlet-<n> record.
(This information is needed when displaying messages to
the user about the application when push connections are detected,
or when the user grants/revokes privileges for the application.)
If the named MIDlet appears more than once in the
suite, the first matching entry is used. -
AllowedSender = a designated filter that restricts which
senders are valid for launching the requested MIDlet.
The syntax and semantics of the AllowedSender field
depend on the addressing format used for the protocol.
However, every syntax for this field MUST support using the wildcard
characters "*" and "?". The semantics of those wildcard are:
- "*" matches any string, including an empty string
- "?" matches any single character
When the value of this field is just the wildcard character "*",
connections will be accepted from any originating source.
For Push attributes using the datagram and
socket URLs (if supported by the platform), this field
contains a numeric IP address in the same format for IPv4 and IPv6 as
used in the respective URLs (IPv6 address including the square
brackets as in the URL).
It is possible to use the wildcards also in these IP addresses,
e.g. "129.70.40.*" would allow subnet resolution. Note that the port
number is not part of the filter for datagram and
socket connections.
The MIDP specification defines the syntax for
datagram and socket inbound
connections. When other specifications
define push semantics for additional connection types, they
must define the expected syntax for the filter field, as well as
the expected format for the connection URL string.
Example Descriptor File Declarative Notation
The following is a sample descriptor file entry that would reserve
a stream socket at port 79 and a datagram connection at
port 50000. (Port numbers are maintained by IANA
and cover well-known, user-registered and dynamic port numbers)
[See
IANA Port Number Registry]
MIDlet-Push-1: socket://:79, com.sun.example.SampleChat, *
MIDlet-Push-2: datagram://:50000, com.sun.example.SampleChat, *
Buffered Messages
The requirements for buffering of messages are specific
to each protocol used for Push and are defined separately
for each protocol. There is no general requirement related
to buffering that would apply to all protocols. If the
implementation buffers messages, these messages MUST
be provided to the MIDlet when the
MIDlet is started and it opens the related
Connection that it has registered for Push.
When datagram connections are supported with Push, the
implementation MUST guarantee that when a MIDlet
registered for datagram Push is started in response to an incoming
datagram, at least the datagram that caused the startup of the
MIDlet is buffered by the implementation and will be
available to the MIDlet when the MIDlet
opens the UDPDatagramConnection after startup.
When socket connections are supported with Push, the
implementation MUST guarantee that when a MIDlet
registered for socket Push is started in response to
an incoming socket connection, this connection can
be accepted by the MIDlet by opening the
ServerSocketConnection after startup, provided
that the connection hasn't timed out meanwhile.
Connection vs Push Registration Support
Not all generic connections will be appropriate for use
as push application transport. Even if a protocol is supported
on the device as an inbound connection type, it is not required
to be enabled as a valid push mechanism. e.g. a platform might
support server socket connections in a MIDlet,
but might not support inbound socket connections for push
launch capability.
A ConnectionNotFoundException is thrown from
the registerConnection and from the
registerAlarm methods, when the platform
does not support that optional capability.
AMS Connection Handoff
Responsibility for registered push connections is shared between
the AMS and the MIDlet that handles the I/O
operations on the inbound connection. To prevent any data
from being lost, an application is responsible for
all I/O operations on the connection from the time it calls
Connector.open()
until it calls Connection.close().
The AMS listens for inbound connection notifications. This
MAY be handled via a native callback or polling mechanism
looking for new inbound data. The AMS is
responsible for enforcing the
Security of PushRegistry
and presenting notifications (if any) to the user before invoking
the MIDlet suite.
The AMS is responsible for the shutdown of any running
applications (if necessary) prior to the invocation of
the push MIDlet method.
After the AMS has started the push application, the
MIDlet is responsible for opening the
connections and for all subsequent I/O operations.
An application that needs to perform blocking I/O
operations SHOULD use a separate thread to allow
for interactive user operations.
Once the application has been started and the connection
has been opened, the AMS is no longer responsible for
listening for push notifications for that connection.
The application is
responsible for reading all inbound data.
If an application has finished with all inbound data
it MAY close() the connection.
If the connection is closed,
then neither the AMS nor the application
will be listening for push notifications. Inbound data
could be lost, if the application closes the connection
before all data has been received.
When the application is destroyed, the AMS resumes its
responsibility to watch for inbound connections.
A push application SHOULD behave in a predictable manner
when handling asynchronous data via the push mechanism.
A well behaved application SHOULD inform the user that
data has been processed. (While it is possible to write
applications that do not use any user visible interfaces,
this could lead to a confused end user experience to
launch an application that only performs a background
function.)
Dynamic Connections Registered from a Running MIDlet
There are cases when defining a well known port registered
with IANA is not necessary.
Simple applications may just wish to exchange data using a private
protocol between a MIDlet and server application.
To accommodate this type of application, a mechanism is provided
to dynamically allocate a connection and to register
that information, as if it was known, when the application was
installed. This information can then be sent to an agent on the network to
use as the mechanism to communicate with the registered
MIDlet.
For instance, if a
UDPDatagramConnection
is opened and a port number,
was not specified, then the application is
requesting a dynamic port
to be allocated from the ports that are currently available. By
calling PushRegistry.registerConnection() the
MIDlet informs the AMS that it is the target for
inbound communication, even
after the MIDlet has been destroyed (See
MIDlet life cycle for
definition of "destroyed" state). If the application is deleted from the
phone, then its dynamic communication connections are unregistered
automatically.
AMS Runtime Handling - Implementation Notes
During installation each MIDlet that is expecting
inbound communication
on a well known address has the information recorded with the
AMS from the push registration attribute in the manifest or
application descriptor file. Once the installation has been
successfully completed,
(e.g. For the OTA recommended practices - when the Installation
notification message has been successfully transmitted, the
application is officially installed.)
the MIDlet MAY then receive inbound communication.
e.g. the push notification event.
When the AMS is started, it checks the list of registered
connections and begins listening for inbound communication.
When a notification arrives the AMS starts the registered
MIDlet.
The MIDlet then opens
the connection with Connector.open() method to
perform whatever I/O operations are needed for the particular
connection type. e.g. for a server socket the application
uses acceptAndOpen() to get the socket connected
and for a datagram connection the application uses
receive() to read the delivered message.
For message oriented transports the inbound message MAY be
read by the AMS and saved for delivery to the MIDlet
when it requests to read the data. For stream oriented transports
the connection MAY be lost if the connection is not
accepted before the server end of the connection request
timeouts.
When a MIDlet is started in response to a registered
push connection notification, it is platform dependent what
happens to the current running application. The MIDlet
life cycle defines the expected behaviors that an interrupted
MIDlet could see from a call to pauseApp()
or from destroyApp().
Sample Usage Scenarios
Usage scenario 1:
The suite includes a MIDlet with a well
known port for communication.
During the startApp processing
a thread is launched to handle the incoming data.
Using a separate thread is the recommended practice
for avoiding conflicts between blocking I/O operations
and the normal user interaction events. The
thread continues to receive messages until the
MIDlet is destroyed.
Sample Chat Descriptor File -
In this sample, the descriptor file includes
a static push
connection registration. It also includes
an indication that this MIDlet
requires permission to use a datagram connection
for inbound push messages.
(See
Security of Push Functions in the package
overview for details about MIDlet permissions.)
Note: this sample is appropriate for bursts of
datagrams.
It is written to loop on the connection, processing
received messages.
MIDlet-Name: SunNetwork - Chat Demo
MIDlet-Version: 1.0
MIDlet-Vendor: Sun Microsystems, Inc.
MIDlet-Description: Network demonstration programs for MIDP
MicroEdition-Profile: MIDP-2.0
MicroEdition-Configuration: CLDC-1.0
MIDlet-1: InstantMessage, /icons/Chat.png, example.chat.SampleChat, *
MIDlet-Push-1: datagram://:79, example.chat.SampleChat, *
MIDlet-Permissions: javax.microedition.io.PushRegistry, \\
javax.microedition.io.Connector.datagramreceiver
Sample Chat MIDlet Processing -
public class SampleChat extends MIDlet {
// Current inbound message connection.
DatagramConnection conn;
// Flag to terminate the message reading thread.
boolean done_reading;
public void startApp() {
// List of active connections.
String connections[];
// Check to see if this session was started due to
// inbound connection notification.
connections = PushRegistry.listConnections(true);
// Start an inbound message thread for available
// inbound messages for the statically configured
// connection in the descriptor file.
for (int i=0; i < connections.length; i++) {
Thread t = new Thread (new MessageHandler(
connections[i]));
t.start();
}
...
}
}
// Stop reading inbound messages and release the push
// connection to the AMS listener.
public void destroyApp(boolean conditional) {
done_reading = true;
if (conn != null)
conn.close();
// Optionally, notify network service that we're
// done with the current session.
...
}
// Optionally, notify network service.
public void pauseApp() {
...
}
// Inner class to handle inbound messages on a separate thread.
class MessageHandler implements Runnable {
String connUrl ;
MessageHandler(String url) {
connUrl = url ;
}
// Fetch messages in a blocking receive loop.
public void run() {
try {
// Get a connection handle for inbound messages
// and a buffer to hold the inbound message.
DatagramConnection conn = (DatagramConnection)
Connector.open(connUrl);
Datagram data = conn.newDatagram(conn.getMaximumLength());
// Read the inbound messages
while (!done_reading) {
conn.receive(data);
...
}
} catch (IOException ioe) {
...
}
...
Usage scenario 2:
The suite includes a MIDlet
that dynamically allocates port the first time
it is started.
Sample Ping Descriptor File -
In this sample, the descriptor file includes an
entry indicating that
the application will need permission to use the datagram
connection for inbound push messages. The dynamic connection
is allocated in the constructor the first time it is run.
The open connection is used during this session and
can be reopened in a subsequent session in response to
a inbound connection notification.
MIDlet-Name: SunNetwork - Demos
MIDlet-Version: 1.0
MIDlet-Vendor: Sun Microsystems, Inc.
MIDlet-Description: Network demonstration programs for MIDP
MicroEdition-Profile: MIDP-2.0
MicroEdition-Configuration: CLDC-1.0
MIDlet-1: JustCallMe, /icons/Ping.png, example.ping.SamplePingMe, *
MIDlet-Permissions: javax.microedition.io.PushRegistry, \\
javax.microedition.io.Connector.datagramreceiver
Sample Ping MIDlet Processing -
public class SamplePingMe extends MIDlet {
// Name of the current application for push registration.
String myName = "example.chat.SamplePingMe";
// List of registered push connections.
String connections[];
// Inbound datagram connection
UDPDatagramConnection dconn;
public SamplePingMe() {
// Check to see if the ping connection has been registered.
// This is a dynamic connection allocated on first
// time execution of this MIDlet.
connections = PushRegistry.listConnections(false);
if (connections.length == 0) {
// Request a dynamic port for out-of-band notices.
// (Omitting the port number let's the system allocate
// an available port number.)
try {
dconn = (UDPDatagramConnection)
Connector.open("datagram://");
String dport = "datagram://:" + dconn.getLocalPort();
// Register the port so the MIDlet will wake up, if messages
// are posted after the MIDlet exits.
PushRegistry.registerConnection(dport, myName, "*");
// Post my datagram address to the network
...
} catch (IOException ioe) {
...
} catch (ClassNotFoundException cnfe) {
...
}
}
public void startApp() {
// Open the connection if it's not already open.
if (dconn == null) {
// This is not the first time this is run, because the
// dconn hasn't been opened by the constructor.
// Check if the startup has been due to an incoming
// datagram.
connections = PushRegistry.listConnections(true);
if (connections.length > 0) {
// There is a pending datagram that can be received.
dconn = (UDPDatagramConnection)
Connector.open(connections[0]);
// Read the datagram
Datagram d = dconn.newDatagram(dconn.getMaximumLength());
dconn.receive(d);
} else {
// There are not any pending datagrams, but open
// the connection for later use.
connections = PushRegistry.listConnections(false);
if (connections.length > 0) {
dconn = (UDPDatagramConnection)
Connector.open(connections[0]);
}
}
}
public void destroyApp(boolean unconditional) {
// Close the connection before exiting
if(dconn != null){
dconn.close()
dconn = null
}
}
...
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