public interface DatagramConnection extends Connection
Reminder: Since the CLDC Specification does not define any actual network protocol implementations, the syntax for datagram addressing is not defined in the CLDC Specification. Rather, syntax definition takes place at the level of J2ME profiles such as MIDP.
In the sample implementation that is provided as part of the CLDC implementation, the following addressing scheme is used:
The parameter string describing the target of a connection in the CLDC implementation takes the following form:
{protocol}://[{host}]:[{port}]
A datagram connection can be opened in a "client" mode or "server" mode.
If the "//{host}" part is missing then the connection is opened as
a "server" (by "server", we mean that a client application initiates
communication). When the "//{host}" part is specified, the connection
is opened as a "client".
Examples:
A datagram connection for accepting datagrams
datagram://:1234
A datagram connection for sending to a server:
datagram://123.456.789.12:1234
Note that the port number in "server mode" (unspecified host name) is that of the receiving port. The port number in "client mode" (host name specified) is that of the target port. The reply-to port in both cases is never unspecified. In "server mode", the same port number is used for both receiving and sending. In "client mode", the reply-to port is always dynamically allocated.
Also note that the allocation of datagram objects is done in a
more abstract way than in Java 2 Standard Edition (J2SE).
Instead of providing a concrete DatagramPacket class,
an abstract Datagram interface is provided. This
is to allow a single platform to support several different datagram
interfaces simultaneously. Datagram objects must be allocated by
calling the newDatagram methods of the
DatagramConnection object.
The resulting object is defined using another interface type
called javax.microedition.io.Datagram.
| Modifier and Type | Method and Description |
|---|---|
int |
getMaximumLength()
Get the maximum length a datagram can be.
|
int |
getNominalLength()
Get the nominal length of a datagram.
|
Datagram |
newDatagram(byte[] buf,
int size)
Create a new datagram object.
|
Datagram |
newDatagram(byte[] buf,
int size,
String addr)
Make a new datagram object.
|
Datagram |
newDatagram(int size)
Create a new datagram object.
|
Datagram |
newDatagram(int size,
String addr)
Create a new datagram object.
|
void |
receive(Datagram dgram)
Receive a datagram.
|
void |
send(Datagram dgram)
Send a datagram.
|
closeint getMaximumLength()
throws IOException
newDatagram method, and the
maximum size of the datagram that can be sent
or received.IOException - If an I/O error occurs.int getNominalLength()
throws IOException
IOException - If an I/O error occurs.void send(Datagram dgram) throws IOException
Datagram object includes
the information indicating the data to be sent, its length,
and the address of the receiver. The method sends length
bytes starting at the current offset of the
Datagram object, where length
and offset are internal state variables
of the Datagram object.dgram - A datagram.IOException - If an I/O error occurs.InterruptedIOException - Timeout or interrupt occurred.void receive(Datagram dgram) throws IOException
Datagram object is filled with
the data received, starting at the location determined by
the offset state variable, and the data is
ready to be read using the methods of the
DataInput interface.
This method blocks until a datagram is received. The internal
length state variable in the Datagram
object contains the length of the received datagram. If the
received data is longer than the length of the internal buffer
minus offset, data is truncated.
This method does not change the internal read/write state
variable of the Datagram object. Use method
Datagram.reset to change the pointer before
reading if necessary.
dgram - A datagram.IOException - If an I/O error occurs.InterruptedIOException - Timeout or interrupt occurred.Datagram newDatagram(int size) throws IOException
size - The size of the buffer needed
for the datagramIOException - If an I/O error occurs.IllegalArgumentException - if the size is negative
or larger than the maximum sizeDatagram newDatagram(int size, String addr) throws IOException
size - The size of the buffer needed
for the datagramaddr - The I/O address to which the datagram
will be sentIOException - If an I/O error occurs.IllegalArgumentException - if the size is negative or
larger than the maximum size, or if the
address parameter is invalidDatagram newDatagram(byte[] buf, int size) throws IOException
buf - The buffer to be used for the datagramsize - The size of the buffer needed
for the datagramIOException - If an I/O error occurs.IllegalArgumentException - if the size is negative or
larger than the maximum size or the given
buffer's length, or if the buffer parameter
is invalidDatagram newDatagram(byte[] buf, int size, String addr) throws IOException
buf - The buffer to be used for the datagramsize - The size of the buffer needed
for the datagramaddr - The I/O address to which the datagram
will be sentIOException - If an I/O error occurs.IllegalArgumentException - if the size is negative or
larger than the maximum size or the given
buffer's length, or if the address or
buffer parameter is invalid