Java UDP 网络编程 示例 -Java学习笔记（30）

 Java UDP网络编程主要通过 DatagramSocket和DatagramPacket 两个类实现的，下面是一个示例程序，
Server监听UDP 2000端口并把收到的Long类型数值打印出来
Client则通过输入获得Long类型的数值，并把它发给Server

Server：

/**//* Coding by nyzhl */
import java.net.*;
import java.io.*;

public class DatagramServer ...{
    public static void main (String[] args) ...{
        DatagramSocket ds = null;
        try ...{
            ds = new DatagramSocket(2000);
        }
        catch (SocketException e) ...{
            e.printStackTrace();
            System.exit(-1);
        }
        byte[] buffer = new byte[1024];
        DatagramPacket dp = new DatagramPacket(buffer,buffer.length);
        while (true) ...{
            DataInputStream in = new DataInputStream (
                new ByteArrayInputStream (buffer)
            );
            try ...{
                ds.receive(dp);
                System.out.println(in.readLong());
                in.close();
            }
            catch (IOException e) ...{
                e.printStackTrace();
                continue;
            }
        }
        //ds.close(); JDK提示"无法访问的语句"
        //因为前面是死循环，无论如何也执行不到后面的语句
    }
}

Client：

/**//* coding by nyzhl */
import java.net.*;
import java.io.*;

public class DatagramClient ...{
    public static void main (String[] args) ...{
        DatagramSocket ds = null;
        try ...{
            ds = new DatagramSocket();
        }
        catch (SocketException e) ...{
            e.printStackTrace();
            System.exit(-1);
        }
        BufferedReader typeReader = new BufferedReader (
            new InputStreamReader(System.in)
        );
        long data = 0;
        while(true) ...{
            ByteArrayOutputStream bytesOut = new ByteArrayOutputStream(); 
            DataOutputStream dataOut = new DataOutputStream (bytesOut);
            try ...{
                data = Long.parseLong(typeReader.readLine());
                dataOut.writeLong(data);
                dataOut.flush();
                byte[] buffer = bytesOut.toByteArray();
                DatagramPacket dp = new DatagramPacket(
                    buffer,
                    buffer.length,
                    new InetSocketAddress("127.0.0.1",2000)
                );
                ds.send(dp);
                dataOut.close();
                bytesOut.close();
            }
            catch (SocketException e) ...{
                System.err.println("Socket Error!");
                continue;
            }
            catch (IOException e) ...{
                System.err.println("IO Error!");
                continue;
            }
            catch (Exception e) ...{
                e.printStackTrace();
                continue;
            }
        }
        //ds.close(); JDK提示"无法访问的语句"
        //因为前面是死循环，无论如何也执行不到后面的语句
    }
}

 

下面参看API文档
Class DatagramSocket：

Constructor Summary
	DatagramSocket()           Constructs a datagram socket and binds it to any available port on the local host machine.
protected	DatagramSocket(DatagramSocketImpl impl)           Creates an unbound datagram socket with the specified DatagramSocketImpl.
	DatagramSocket(int port)           Constructs a datagram socket and binds it to the specified port on the local host machine.
	DatagramSocket(int port, InetAddress laddr)           Creates a datagram socket, bound to the specified local address.
	DatagramSocket(SocketAddress bindaddr)           Creates a datagram socket, bound to the specified local socket address.

 

Method Summary
void	bind(SocketAddress addr)           Binds this DatagramSocket to a specific address & port.
void	close()           Closes this datagram socket.
void	connect(InetAddress address, int port)           Connects the socket to a remote address for this socket.
void	connect(SocketAddress addr)           Connects this socket to a remote socket address (IP address + port number).
void	disconnect()           Disconnects the socket.
boolean	getBroadcast()           Tests if SO_BROADCAST is enabled.
DatagramChannel	getChannel()           Returns the unique DatagramChannel object associated with this datagram socket, if any.
InetAddress	getInetAddress()           Returns the address to which this socket is connected.
InetAddress	getLocalAddress()           Gets the local address to which the socket is bound.
int	getLocalPort()           Returns the port number on the local host to which this socket is bound.
SocketAddress	getLocalSocketAddress()           Returns the address of the endpoint this socket is bound to, or null if it is not bound yet.
int	getPort()           Returns the port for this socket.
int	getReceiveBufferSize()           Get value of the SO_RCVBUF option for this DatagramSocket, that is the buffer size used by the platform for input on this DatagramSocket.
SocketAddress	getRemoteSocketAddress()           Returns the address of the endpoint this socket is connected to, or null if it is unconnected.
boolean	getReuseAddress()           Tests if SO_REUSEADDR is enabled.
int	getSendBufferSize()           Get value of the SO_SNDBUF option for this DatagramSocket, that is the buffer size used by the platform for output on this DatagramSocket.
int	getSoTimeout()           Retrieve setting for SO_TIMEOUT.
int	getTrafficClass()           Gets traffic class or type-of-service in the IP datagram header for packets sent from this DatagramSocket.
boolean	isBound()           Returns the binding state of the socket.
boolean	isClosed()           Returns whether the socket is closed or not.
boolean	isConnected()           Returns the connection state of the socket.
void	receive(DatagramPacket p)           Receives a datagram packet from this socket.
void	send(DatagramPacket p)           Sends a datagram packet from this socket.
void	setBroadcast(boolean on)           Enable/disable SO_BROADCAST.
static void	setDatagramSocketImplFactory(DatagramSocketImplFactory fac)           Sets the datagram socket implementation factory for the application.
void	setReceiveBufferSize(int size)           Sets the SO_RCVBUF option to the specified value for this DatagramSocket.
void	setReuseAddress(boolean on)           Enable/disable the SO_REUSEADDR socket option.
void	setSendBufferSize(int size)           Sets the SO_SNDBUF option to the specified value for this DatagramSocket.
void	setSoTimeout(int timeout)           Enable/disable SO_TIMEOUT with the specified timeout, in milliseconds.
void	setTrafficClass(int tc)           Sets traffic class or type-of-service octet in the IP datagram header for datagrams sent from this DatagramSocket.

Class DatagramPacket：

Constructor Summary
DatagramPacket(byte[] buf, int length)           Constructs a DatagramPacket for receiving packets of length length.
DatagramPacket(byte[] buf, int length, InetAddress address, int port)           Constructs a datagram packet for sending packets of length length to the specified port number on the specified host.
DatagramPacket(byte[] buf, int offset, int length)           Constructs a DatagramPacket for receiving packets of length length, specifying an offset into the buffer.
DatagramPacket(byte[] buf, int offset, int length, InetAddress address, int port)           Constructs a datagram packet for sending packets of length length with offset ioffsetto the specified port number on the specified host.
DatagramPacket(byte[] buf, int offset, int length, SocketAddress address)           Constructs a datagram packet for sending packets of length length with offset ioffsetto the specified port number on the specified host.
DatagramPacket(byte[] buf, int length, SocketAddress address)           Constructs a datagram packet for sending packets of length length to the specified port number on the specified host.

 

Method Summary
InetAddress	getAddress()           Returns the IP address of the machine to which this datagram is being sent or from which the datagram was received.
byte[]	getData()           Returns the data buffer.
int	getLength()           Returns the length of the data to be sent or the length of the data received.
int	getOffset()           Returns the offset of the data to be sent or the offset of the data received.
int	getPort()           Returns the port number on the remote host to which this datagram is being sent or from which the datagram was received.
SocketAddress	getSocketAddress()           Gets the SocketAddress (usually IP address + port number) of the remote host that this packet is being sent to or is coming from.
void	setAddress(InetAddress iaddr)           Sets the IP address of the machine to which this datagram is being sent.
void	setData(byte[] buf)           Set the data buffer for this packet.
void	setData(byte[] buf, int offset, int length)           Set the data buffer for this packet.
void	setLength(int length)           Set the length for this packet.
void	setPort(int iport)           Sets the port number on the remote host to which this datagram is being sent.
void	setSocketAddress(SocketAddress address)           Sets the SocketAddress (usually IP address + port number) of the remote host to which this datagram is being sent.