DatagramChannel

DatagramChannel

java.nio.channels

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Java 1.4

closeable

This class implements a communication channel based on network datagrams. Obtain a DatagramChannel by calling the static open ( ) method. Call socket( ) to obtain the java.net.DatagramSocket object on which the channel is based if you need to set any socket options to control low-level networking details.

The send( ) method sends the remaining bytes of the specified ByteBuffer to the host and port specified in the java.net.SocketAddress in the form of a datagram. receive( ) does the opposite : it receives a datagram, stores its content into the specified buffer ( discarding any bytes that do not fit) and then returns a SocketAddress that specifies the sender of the datagram (or returns null if the channel was in nonblocking mode and no datagram was waiting).

The send( ) and receive( ) methods typically perform security checks on each invocation to see if the application has permissions to communicate with the remote host. If your application will use a DatagramChannel to exchange datagrams with a single remote host and port, use the connect( ) method to connect to a specified SocketAddress . The connect( ) method performs the required security checks once and allows future communication with the specified address without the overhead. Once a DatagramChannel is connected, you can use the standard read( ) and write( ) methods defined by the ReadableByteChannel , WritableByteChannel , GatheringByteChannel and ScatteringByteChannel interfaces. Like the receive( ) method, the read( ) methods silently discard any received bytes that do not fit in the specified ByteBuffer . The read( ) and write( ) methods throw a NotYetConnected exception if connect( ) has not been called.

DatagramChannel is a SelectableChannel ; its validOps( ) method specifies that read and write operations may be selected. DatagramChannel objects are thread-safe. Read and write operations may proceed concurrently, but the class ensures that only one thread may read and one thread write at a time.

Figure 13-2. java.nio.channels.DatagramChannel

 public abstract class  DatagramChannel  extends java.nio.channels.spi. AbstractSelectableChannel implements ByteChannel, GatheringByteChannel, ScatteringByteChannel {  // Protected Constructors  protected  DatagramChannel  (java.nio.channels.spi.SelectorProvider  provider  );  // Public Class Methods  public static DatagramChannel  open  ( ) throws java.io.IOException;  // Public Instance Methods  public abstract DatagramChannel  connect  (java.net.SocketAddress  remote  )  throws java.io.IOException;        public abstract DatagramChannel  disconnect  ( ) throws java.io.IOException;        public abstract boolean  isConnected  ( );        public abstract java.net.SocketAddress  receive  (java.nio.ByteBuffer  dst  )  throws java.io.IOException;        public abstract int  send  (java.nio.ByteBuffer  src  , java.net.SocketAddress  target  ) throws java.io.IOException;        public abstract java.net.DatagramSocket  socket  ( );  // Methods Implementing GatheringByteChannel  public final long  write  (java.nio.ByteBuffer[ ]  srcs  )  throws java.io.IOException;        public abstract long  write  (java.nio.ByteBuffer[ ]  srcs  , int  offset  ,  int  length  ) throws java.io.IOException;  // Methods Implementing ReadableByteChannel  public abstract int  read  (java.nio.ByteBuffer  dst  )  throws java.io.IOException;  // Methods Implementing ScatteringByteChannel  public final long  read  (java.nio.ByteBuffer[ ]  dsts  )  throws java.io.IOException;        public abstract long  read  (java.nio.ByteBuffer[ ]  dsts  , int  offset  ,  int  length  ) throws java.io.IOException;  // Methods Implementing WritableByteChannel  public abstract int  write  (java.nio.ByteBuffer  src  )  throws java.io.IOException;  // Public Methods Overriding SelectableChannel  public final int  validOps  ( );  constant  } 

Returned By

java.net.DatagramSocket.getChannel( ) , java.nio.channels.spi.SelectorProvider.openDatagramChannel( )