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DatagramSocket.javaAPI DocJava SE 6 API42137Tue Jun 10 00:25:40 BST 2008java.net

DatagramSocket

public class DatagramSocket extends Object
This class represents a socket for sending and receiving datagram packets.

A datagram socket is the sending or receiving point for a packet delivery service. Each packet sent or received on a datagram socket is individually addressed and routed. Multiple packets sent from one machine to another may be routed differently, and may arrive in any order.

UDP broadcasts sends are always enabled on a DatagramSocket. In order to receive broadcast packets a DatagramSocket should be bound to the wildcard address. In some implementations, broadcast packets may also be received when a DatagramSocket is bound to a more specific address.

Example: DatagramSocket s = new DatagramSocket(null); s.bind(new InetSocketAddress(8888)); Which is equivalent to: DatagramSocket s = new DatagramSocket(8888); Both cases will create a DatagramSocket able to receive broadcasts on UDP port 8888.

author
Pavani Diwanji
version
1.101, 06/08/06
see
java.net.DatagramPacket
see
java.nio.channels.DatagramChannel
since
JDK1.0

Fields Summary
private boolean
created
Various states of this socket.
private boolean
bound
private boolean
closed
private Object
closeLock
DatagramSocketImpl
impl
boolean
oldImpl
Are we using an older DatagramSocketImpl?
static final int
ST_NOT_CONNECTED
static final int
ST_CONNECTED
static final int
ST_CONNECTED_NO_IMPL
int
connectState
InetAddress
connectedAddress
int
connectedPort
static Class
implClass
static DatagramSocketImplFactory
factory
The factory for all datagram sockets.
Constructors Summary
public DatagramSocket()
Constructs a datagram socket and binds it to any available port on the local host machine. The socket will be bound to the wildcard address, an IP address chosen by the kernel.

If there is a security manager, its checkListen method is first called with 0 as its argument to ensure the operation is allowed. This could result in a SecurityException.

exception
SocketException if the socket could not be opened, or the socket could not bind to the specified local port.
exception
SecurityException if a security manager exists and its checkListen method doesn't allow the operation.
see
SecurityManager#checkListen

	// create a datagram socket.
	createImpl();
	try {
	    bind(new InetSocketAddress(0));
	} catch (SocketException se) {
	    throw se;
	} catch(IOException e) {
	    throw new SocketException(e.getMessage());
	}
    
protected DatagramSocket(DatagramSocketImpl impl)
Creates an unbound datagram socket with the specified DatagramSocketImpl.

param
impl an instance of a DatagramSocketImpl the subclass wishes to use on the DatagramSocket.
since
1.4

        if (impl == null)
            throw new NullPointerException();
	this.impl = impl;
	checkOldImpl();
    
public DatagramSocket(SocketAddress bindaddr)
Creates a datagram socket, bound to the specified local socket address.

If, if the address is null, creates an unbound socket.

If there is a security manager, its checkListen method is first called with the port from the socket address as its argument to ensure the operation is allowed. This could result in a SecurityException.

param
bindaddr local socket address to bind, or null for an unbound socket.
exception
SocketException if the socket could not be opened, or the socket could not bind to the specified local port.
exception
SecurityException if a security manager exists and its checkListen method doesn't allow the operation.
see
SecurityManager#checkListen
since
1.4

	// create a datagram socket.
	createImpl();
	if (bindaddr != null) {
	    bind(bindaddr);
	}
    
public DatagramSocket(int port)
Constructs a datagram socket and binds it to the specified port on the local host machine. The socket will be bound to the wildcard address, an IP address chosen by the kernel.

If there is a security manager, its checkListen method is first called with the port argument as its argument to ensure the operation is allowed. This could result in a SecurityException.

param
port port to use.
exception
SocketException if the socket could not be opened, or the socket could not bind to the specified local port.
exception
SecurityException if a security manager exists and its checkListen method doesn't allow the operation.
see
SecurityManager#checkListen

	this(port, null);
    
public DatagramSocket(int port, InetAddress laddr)
Creates a datagram socket, bound to the specified local address. The local port must be between 0 and 65535 inclusive. If the IP address is 0.0.0.0, the socket will be bound to the wildcard address, an IP address chosen by the kernel.

If there is a security manager, its checkListen method is first called with the port argument as its argument to ensure the operation is allowed. This could result in a SecurityException.

param
port local port to use
param
laddr local address to bind
exception
SocketException if the socket could not be opened, or the socket could not bind to the specified local port.
exception
SecurityException if a security manager exists and its checkListen method doesn't allow the operation.
see
SecurityManager#checkListen
since
JDK1.1

	this(new InetSocketAddress(laddr, port));
    
Methods Summary
public synchronized voidbind(java.net.SocketAddress addr)
Binds this DatagramSocket to a specific address & port.

If the address is null, then the system will pick up an ephemeral port and a valid local address to bind the socket.

param
addr The address & port to bind to.
throws
SocketException if any error happens during the bind, or if the socket is already bound.
throws
SecurityException if a security manager exists and its checkListen method doesn't allow the operation.
throws
IllegalArgumentException if addr is a SocketAddress subclass not supported by this socket.
since
1.4

	if (isClosed())
	    throw new SocketException("Socket is closed");
	if (isBound())
	    throw new SocketException("already bound");
	if (addr == null)
	    addr = new InetSocketAddress(0);
	if (!(addr instanceof InetSocketAddress))
	    throw new IllegalArgumentException("Unsupported address type!");
	InetSocketAddress epoint = (InetSocketAddress) addr;
	if (epoint.isUnresolved())
	    throw new SocketException("Unresolved address");
	SecurityManager sec = System.getSecurityManager();
	if (sec != null) {
	    sec.checkListen(epoint.getPort());
	}
	try {
	    getImpl().bind(epoint.getPort(), 
			   epoint.getAddress());
	} catch (SocketException e) {
	    getImpl().close();
	    throw e;
	}
	bound = true;
    
private voidcheckOldImpl()

	if (impl == null)
	    return;
	// DatagramSocketImpl.peekdata() is a protected method, therefore we need to use
	// getDeclaredMethod, therefore we need permission to access the member
	try {
	    AccessController.doPrivileged(new PrivilegedExceptionAction() {
		    public Object run() throws NoSuchMethodException {
			Class[] cl = new Class[1];
			cl[0] = DatagramPacket.class;
			impl.getClass().getDeclaredMethod("peekData", cl);
			return null;
		    }
		});
	} catch (java.security.PrivilegedActionException e) {
	    oldImpl = true;
	}
    
public voidclose()
Closes this datagram socket.

Any thread currently blocked in {@link #receive} upon this socket will throw a {@link SocketException}.

If this socket has an associated channel then the channel is closed as well.

revised
1.4
spec
JSR-51

	synchronized(closeLock) {
	    if (isClosed())
		return;
	    impl.close();
	    closed = true;
	}
    
public voidconnect(java.net.InetAddress address, int port)
Connects the socket to a remote address for this socket. When a socket is connected to a remote address, packets may only be sent to or received from that address. By default a datagram socket is not connected.

If the remote destination to which the socket is connected does not exist, or is otherwise unreachable, and if an ICMP destination unreachable packet has been received for that address, then a subsequent call to send or receive may throw a PortUnreachableException. Note, there is no guarantee that the exception will be thrown.

A caller's permission to send and receive datagrams to a given host and port are checked at connect time. When a socket is connected, receive and send will not perform any security checks on incoming and outgoing packets, other than matching the packet's and the socket's address and port. On a send operation, if the packet's address is set and the packet's address and the socket's address do not match, an IllegalArgumentException will be thrown. A socket connected to a multicast address may only be used to send packets.

param
address the remote address for the socket
param
port the remote port for the socket.
exception
IllegalArgumentException if the address is null, or the port is out of range.
exception
SecurityException if the caller is not allowed to send datagrams to and receive datagrams from the address and port.
see
#disconnect
see
#send
see
#receive

	try {
	    connectInternal(address, port);
	} catch (SocketException se) { 
	    throw new Error("connect failed", se);
	}
    
public voidconnect(java.net.SocketAddress addr)
Connects this socket to a remote socket address (IP address + port number).

param
addr The remote address.
throws
SocketException if the connect fails
throws
IllegalArgumentException if addr is null or addr is a SocketAddress subclass not supported by this socket
since
1.4
see
#connect

	if (addr == null)
	    throw new IllegalArgumentException("Address can't be null");
	if (!(addr instanceof InetSocketAddress))
	    throw new IllegalArgumentException("Unsupported address type");
	InetSocketAddress epoint = (InetSocketAddress) addr;
	if (epoint.isUnresolved())
	    throw new SocketException("Unresolved address");
	connectInternal(epoint.getAddress(), epoint.getPort());
    
private synchronized voidconnectInternal(java.net.InetAddress address, int port)
Connects this socket to a remote socket address (IP address + port number). Binds socket if not already bound.

param
addr The remote address.
param
port The remote port
throws
SocketException if binding the socket fails.


                                   		               
             
        if (port < 0 || port > 0xFFFF) {
            throw new IllegalArgumentException("connect: " + port);
        }
        if (address == null) {
            throw new IllegalArgumentException("connect: null address");
        }
        if (isClosed())
            return;
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            if (address.isMulticastAddress()) {
                security.checkMulticast(address);
            } else {
                security.checkConnect(address.getHostAddress(), port);
                security.checkAccept(address.getHostAddress(), port);
            }
        }

	if (!isBound())
	  bind(new InetSocketAddress(0));

	// old impls do not support connect/disconnect
	if (oldImpl) {
	    connectState = ST_CONNECTED_NO_IMPL;
	} else {
	    try {
	        getImpl().connect(address, port);

		// socket is now connected by the impl
		connectState = ST_CONNECTED;
	    } catch (SocketException se) {

		// connection will be emulated by DatagramSocket
		connectState = ST_CONNECTED_NO_IMPL;
	    }
	}

        connectedAddress = address;
        connectedPort = port;
    
voidcreateImpl()


        
	if (impl == null) {
	    if (factory != null) {
		impl = factory.createDatagramSocketImpl();
		checkOldImpl();
	    } else {
		if (implClass == null) {
		    String prefix = null;
		    try {
			prefix = (String) AccessController.doPrivileged(
			    new sun.security.action.GetPropertyAction("impl.prefix", "Plain"));
			implClass = Class.forName("java.net."+prefix+"DatagramSocketImpl");
		    } catch (Exception e) {
			System.err.println("Can't find class: java.net." + 
					   prefix +
					   "DatagramSocketImpl: check impl.prefix property");
		    }
		    if (implClass == null)
			implClass = java.net.PlainDatagramSocketImpl.class;
		}
		try {
		    impl = (DatagramSocketImpl) implClass.newInstance();
		} catch (Exception e) {
		    throw new SocketException("can't instantiate DatagramSocketImpl");
		}
		// No need to do a checkOldImpl() here, we know it's an up to date
		// SocketImpl!
		if (!(impl instanceof java.net.PlainDatagramSocketImpl))
		    checkOldImpl();
	    }
	}
	// creates a udp socket
	impl.create();
	created = true;
    
public voiddisconnect()
Disconnects the socket. This does nothing if the socket is not connected.

see
#connect

	synchronized (this) {
	    if (isClosed())
		return;
	    if (connectState == ST_CONNECTED) {
	    	impl.disconnect ();
	    }
	    connectedAddress = null;
	    connectedPort = -1;
	    connectState = ST_NOT_CONNECTED;
	}
    
public synchronized booleangetBroadcast()
Tests if SO_BROADCAST is enabled.

return
a boolean indicating whether or not SO_BROADCAST is enabled.
exception
SocketException if there is an error in the underlying protocol, such as an UDP error.
since
1.4
see
#setBroadcast(boolean)

	if (isClosed())
	    throw new SocketException("Socket is closed");
        return ((Boolean)(getImpl().getOption(SocketOptions.SO_BROADCAST))).booleanValue();
    
public java.nio.channels.DatagramChannelgetChannel()
Returns the unique {@link java.nio.channels.DatagramChannel} object associated with this datagram socket, if any.

A datagram socket will have a channel if, and only if, the channel itself was created via the {@link java.nio.channels.DatagramChannel#open DatagramChannel.open} method.

return
the datagram channel associated with this datagram socket, or null if this socket was not created for a channel
since
1.4
spec
JSR-51

	return null;
    
java.net.DatagramSocketImplgetImpl()
Get the DatagramSocketImpl attached to this socket, creating it if necessary.

return
the DatagramSocketImpl attached to that DatagramSocket
throws
SocketException if creation fails.
since
1.4

	if (!created)
	    createImpl();
	return impl;
    
public java.net.InetAddressgetInetAddress()
Returns the address to which this socket is connected. Returns null if the socket is not connected.

return
the address to which this socket is connected.

	return connectedAddress;
    
public java.net.InetAddressgetLocalAddress()
Gets the local address to which the socket is bound.

If there is a security manager, its checkConnect method is first called with the host address and -1 as its arguments to see if the operation is allowed.

see
SecurityManager#checkConnect
return
the local address to which the socket is bound, or an InetAddress representing any local address if either the socket is not bound, or the security manager checkConnect method does not allow the operation
since
1.1

	if (isClosed())
	    return null;
	InetAddress in = null;
	try {
	    in = (InetAddress) getImpl().getOption(SocketOptions.SO_BINDADDR);
	    if (in.isAnyLocalAddress()) {
		in = InetAddress.anyLocalAddress();
	    }
	    SecurityManager s = System.getSecurityManager();
	    if (s != null) {
		s.checkConnect(in.getHostAddress(), -1);
	    }
	} catch (Exception e) {
	    in = InetAddress.anyLocalAddress(); // "0.0.0.0"
	}
	return in;
    
public intgetLocalPort()
Returns the port number on the local host to which this socket is bound.

return
the port number on the local host to which this socket is bound.

	if (isClosed())
	    return -1;
	try {
	    return getImpl().getLocalPort();
	} catch (Exception e) {
	    return 0;
	}
    
public java.net.SocketAddressgetLocalSocketAddress()
Returns the address of the endpoint this socket is bound to, or null if it is not bound yet.

return
a SocketAddress representing the local endpoint of this socket, or null if it is not bound yet.
see
#getLocalAddress()
see
#getLocalPort()
see
#bind(SocketAddress)
since
1.4

	if (!isBound())
	    return null;
	return new InetSocketAddress(getLocalAddress(), getLocalPort());
    
public intgetPort()
Returns the port for this socket. Returns -1 if the socket is not connected.

return
the port to which this socket is connected.

	return connectedPort;
    
public synchronized intgetReceiveBufferSize()
Get value of the SO_RCVBUF option for this DatagramSocket, that is the buffer size used by the platform for input on this DatagramSocket.

return
the value of the SO_RCVBUF option for this DatagramSocket
exception
SocketException if there is an error in the underlying protocol, such as an UDP error.
see
#setReceiveBufferSize(int)

	if (isClosed())
	    throw new SocketException("Socket is closed");
	int result = 0;
	Object o = getImpl().getOption(SocketOptions.SO_RCVBUF);
	if (o instanceof Integer) {
	    result = ((Integer)o).intValue();
	}
	return result;
    
public java.net.SocketAddressgetRemoteSocketAddress()
Returns the address of the endpoint this socket is connected to, or null if it is unconnected.

return
a SocketAddress representing the remote endpoint of this socket, or null if it is not connected yet.
see
#getInetAddress()
see
#getPort()
see
#connect(SocketAddress)
since
1.4

	if (!isConnected())
	    return null;
	return new InetSocketAddress(getInetAddress(), getPort());
    
public synchronized booleangetReuseAddress()
Tests if SO_REUSEADDR is enabled.

return
a boolean indicating whether or not SO_REUSEADDR is enabled.
exception
SocketException if there is an error in the underlying protocol, such as an UDP error.
since
1.4
see
#setReuseAddress(boolean)

	if (isClosed())
	    throw new SocketException("Socket is closed");
	Object o = getImpl().getOption(SocketOptions.SO_REUSEADDR);
	return ((Boolean)o).booleanValue();
    
public synchronized intgetSendBufferSize()
Get value of the SO_SNDBUF option for this DatagramSocket, that is the buffer size used by the platform for output on this DatagramSocket.

return
the value of the SO_SNDBUF option for this DatagramSocket
exception
SocketException if there is an error in the underlying protocol, such as an UDP error.
see
#setSendBufferSize

	if (isClosed())
	    throw new SocketException("Socket is closed");
	int result = 0;
	Object o = getImpl().getOption(SocketOptions.SO_SNDBUF);
	if (o instanceof Integer) {
	    result = ((Integer)o).intValue();
	}
	return result;
    
public synchronized intgetSoTimeout()
Retrieve setting for SO_TIMEOUT. 0 returns implies that the option is disabled (i.e., timeout of infinity).

return
the setting for SO_TIMEOUT
throws
SocketException if there is an error in the underlying protocol, such as an UDP error.
since
JDK1.1
see
#setSoTimeout(int)

	if (isClosed())
	    throw new SocketException("Socket is closed");
	if (getImpl() == null)
	    return 0;
	Object o = getImpl().getOption(SocketOptions.SO_TIMEOUT);
	/* extra type safety */
	if (o instanceof Integer) {
	    return ((Integer) o).intValue();
	} else {
	    return 0;
	}
    
public synchronized intgetTrafficClass()
Gets traffic class or type-of-service in the IP datagram header for packets sent from this DatagramSocket.

As the underlying network implementation may ignore the traffic class or type-of-service set using {@link #setTrafficClass(int)} this method may return a different value than was previously set using the {@link #setTrafficClass(int)} method on this DatagramSocket.

return
the traffic class or type-of-service already set
throws
SocketException if there is an error obtaining the traffic class or type-of-service value.
since
1.4
see
#setTrafficClass(int)

	if (isClosed())
	    throw new SocketException("Socket is closed");
        return ((Integer)(getImpl().getOption(SocketOptions.IP_TOS))).intValue();
    
public booleanisBound()
Returns the binding state of the socket.

return
true if the socket succesfuly bound to an address
since
1.4

	return bound;
    
public booleanisClosed()
Returns whether the socket is closed or not.

return
true if the socket has been closed
since
1.4

	synchronized(closeLock) {
	    return closed;
	}
    
public booleanisConnected()
Returns the connection state of the socket.

return
true if the socket succesfuly connected to a server
since
1.4

	return connectState != ST_NOT_CONNECTED;
    
public synchronized voidreceive(java.net.DatagramPacket p)
Receives a datagram packet from this socket. When this method returns, the DatagramPacket's buffer is filled with the data received. The datagram packet also contains the sender's IP address, and the port number on the sender's machine.

This method blocks until a datagram is received. The length field of the datagram packet object contains the length of the received message. If the message is longer than the packet's length, the message is truncated.

If there is a security manager, a packet cannot be received if the security manager's checkAccept method does not allow it.

param
p the DatagramPacket into which to place the incoming data.
exception
IOException if an I/O error occurs.
exception
SocketTimeoutException if setSoTimeout was previously called and the timeout has expired.
exception
PortUnreachableException may be thrown if the socket is connected to a currently unreachable destination. Note, there is no guarantee that the exception will be thrown.
exception
java.nio.channels.IllegalBlockingModeException if this socket has an associated channel, and the channel is in non-blocking mode.
see
java.net.DatagramPacket
see
java.net.DatagramSocket
revised
1.4
spec
JSR-51

      	synchronized (p) {
	    if (!isBound())
		bind(new InetSocketAddress(0));
	    if (connectState == ST_NOT_CONNECTED) {
		// check the address is ok with the security manager before every recv.
		SecurityManager security = System.getSecurityManager();
		if (security != null) {
		    while(true) {
			String peekAd = null;
			int peekPort = 0;
			// peek at the packet to see who it is from.
			if (!oldImpl) {
			    // We can use the new peekData() API
			    DatagramPacket peekPacket = new DatagramPacket(new byte[1], 1);
			    peekPort = getImpl().peekData(peekPacket);
			    peekAd = peekPacket.getAddress().getHostAddress();
			} else {
			    InetAddress adr = new InetAddress();
			    peekPort = getImpl().peek(adr);
			    peekAd = adr.getHostAddress();
			}
			try {
			    security.checkAccept(peekAd, peekPort);
			    // security check succeeded - so now break
			    // and recv the packet.
			    break;
			} catch (SecurityException se) {
			    // Throw away the offending packet by consuming
			    // it in a tmp buffer.
			    DatagramPacket tmp = new DatagramPacket(new byte[1], 1);
			    getImpl().receive(tmp);
			
			    // silently discard the offending packet
			    // and continue: unknown/malicious
			    // entities on nets should not make
			    // runtime throw security exception and
			    // disrupt the applet by sending random
			    // datagram packets.
			    continue;
			} 
		    } // end of while
		}
	    }
	    if (connectState == ST_CONNECTED_NO_IMPL) {
		// We have to do the filtering the old fashioned way since
		// the native impl doesn't support connect or the connect
		// via the impl failed.
		boolean stop = false;
		while (!stop) {
		    // peek at the packet to see who it is from.
		    InetAddress peekAddress = new InetAddress();
		    int peekPort = getImpl().peek(peekAddress);
		    if ((!connectedAddress.equals(peekAddress)) ||
			(connectedPort != peekPort)) {
			// throw the packet away and silently continue
			DatagramPacket tmp = new DatagramPacket(new byte[1], 1);
			getImpl().receive(tmp);
		    } else {
			stop = true;
		    }
		}
	    }
	    // If the security check succeeds, or the datagram is
	    // connected then receive the packet
	    getImpl().receive(p);
	}
    
public voidsend(java.net.DatagramPacket p)
Sends a datagram packet from this socket. The DatagramPacket includes information indicating the data to be sent, its length, the IP address of the remote host, and the port number on the remote host.

If there is a security manager, and the socket is not currently connected to a remote address, this method first performs some security checks. First, if p.getAddress().isMulticastAddress() is true, this method calls the security manager's checkMulticast method with p.getAddress() as its argument. If the evaluation of that expression is false, this method instead calls the security manager's checkConnect method with arguments p.getAddress().getHostAddress() and p.getPort(). Each call to a security manager method could result in a SecurityException if the operation is not allowed.

param
p the DatagramPacket to be sent.
exception
IOException if an I/O error occurs.
exception
SecurityException if a security manager exists and its checkMulticast or checkConnect method doesn't allow the send.
exception
PortUnreachableException may be thrown if the socket is connected to a currently unreachable destination. Note, there is no guarantee that the exception will be thrown.
exception
java.nio.channels.IllegalBlockingModeException if this socket has an associated channel, and the channel is in non-blocking mode.
see
java.net.DatagramPacket
see
SecurityManager#checkMulticast(InetAddress)
see
SecurityManager#checkConnect
revised
1.4
spec
JSR-51

	InetAddress packetAddress = null;
	synchronized (p) {
	    if (isClosed())
		throw new SocketException("Socket is closed");
	    if (connectState == ST_NOT_CONNECTED) {
		// check the address is ok wiht the security manager on every send.
		SecurityManager security = System.getSecurityManager();

		// The reason you want to synchronize on datagram packet
		// is because you dont want an applet to change the address 
		// while you are trying to send the packet for example 
		// after the security check but before the send.
		if (security != null) {
		    if (p.getAddress().isMulticastAddress()) {
			security.checkMulticast(p.getAddress());
		    } else {
			security.checkConnect(p.getAddress().getHostAddress(), 
					      p.getPort());
		    }
		}
	    } else {
		// we're connected
		packetAddress = p.getAddress();
		if (packetAddress == null) {
		    p.setAddress(connectedAddress);
		    p.setPort(connectedPort);
		} else if ((!packetAddress.equals(connectedAddress)) ||
			   p.getPort() != connectedPort) {
		    throw new IllegalArgumentException("connected address " +
						       "and packet address" +
						       " differ");
		}
	    }
	    // Check whether the socket is bound
	    if (!isBound())
		bind(new InetSocketAddress(0));
	    // call the  method to send
	    getImpl().send(p);
        }
    
public synchronized voidsetBroadcast(boolean on)
Enable/disable SO_BROADCAST.

param
on whether or not to have broadcast turned on.
exception
SocketException if there is an error in the underlying protocol, such as an UDP error.
since
1.4
see
#getBroadcast()

	if (isClosed())
	    throw new SocketException("Socket is closed");
        getImpl().setOption(SocketOptions.SO_BROADCAST, Boolean.valueOf(on));
    
public static synchronized voidsetDatagramSocketImplFactory(java.net.DatagramSocketImplFactory fac)
Sets the datagram socket implementation factory for the application. The factory can be specified only once.

When an application creates a new datagram socket, the socket implementation factory's createDatagramSocketImpl method is called to create the actual datagram socket implementation.

Passing null to the method is a no-op unless the factory was already set.

If there is a security manager, this method first calls the security manager's checkSetFactory method to ensure the operation is allowed. This could result in a SecurityException.

param
fac the desired factory.
exception
IOException if an I/O error occurs when setting the datagram socket factory.
exception
SocketException if the factory is already defined.
exception
SecurityException if a security manager exists and its checkSetFactory method doesn't allow the operation.
see
java.net.DatagramSocketImplFactory#createDatagramSocketImpl()
see
SecurityManager#checkSetFactory
since
1.3

        if (factory != null) {
	    throw new SocketException("factory already defined");
	}
 	SecurityManager security = System.getSecurityManager();
 	if (security != null) {
	    security.checkSetFactory();
 	}
 	factory = fac;
    
public synchronized voidsetReceiveBufferSize(int size)
Sets the SO_RCVBUF option to the specified value for this DatagramSocket. The SO_RCVBUF option is used by the the network implementation as a hint to size the underlying network I/O buffers. The SO_RCVBUF setting may also be used by the network implementation to determine the maximum size of the packet that can be received on this socket.

Because SO_RCVBUF is a hint, applications that want to verify what size the buffers were set to should call {@link #getReceiveBufferSize()}.

Increasing SO_RCVBUF may allow the network implementation to buffer multiple packets when packets arrive faster than are being received using {@link #receive(DatagramPacket)}.

Note: It is implementation specific if a packet larger than SO_RCVBUF can be received.

param
size the size to which to set the receive buffer size. This value must be greater than 0.
exception
SocketException if there is an error in the underlying protocol, such as an UDP error.
exception
IllegalArgumentException if the value is 0 or is negative.
see
#getReceiveBufferSize()

	if (size <= 0) {
	    throw new IllegalArgumentException("invalid receive size");
	}
	if (isClosed())
	    throw new SocketException("Socket is closed");
	getImpl().setOption(SocketOptions.SO_RCVBUF, new Integer(size));
    
public synchronized voidsetReuseAddress(boolean on)
Enable/disable the SO_REUSEADDR socket option.

For UDP sockets it may be necessary to bind more than one socket to the same socket address. This is typically for the purpose of receiving multicast packets (See {@link java.net.MulticastSocket}). The SO_REUSEADDR socket option allows multiple sockets to be bound to the same socket address if the SO_REUSEADDR socket option is enabled prior to binding the socket using {@link #bind(SocketAddress)}.

Note: This functionality is not supported by all existing platforms, so it is implementation specific whether this option will be ignored or not. However, if it is not supported then {@link #getReuseAddress()} will always return false.

When a DatagramSocket is created the initial setting of SO_REUSEADDR is disabled.

The behaviour when SO_REUSEADDR is enabled or disabled after a socket is bound (See {@link #isBound()}) is not defined.

param
on whether to enable or disable the
exception
SocketException if an error occurs enabling or disabling the SO_RESUEADDR socket option, or the socket is closed.
since
1.4
see
#getReuseAddress()
see
#bind(SocketAddress)
see
#isBound()
see
#isClosed()

	if (isClosed())
	    throw new SocketException("Socket is closed");
	// Integer instead of Boolean for compatibility with older DatagramSocketImpl
        if (oldImpl)
	    getImpl().setOption(SocketOptions.SO_REUSEADDR, new Integer(on?-1:0));
	else
	    getImpl().setOption(SocketOptions.SO_REUSEADDR, Boolean.valueOf(on));
    
public synchronized voidsetSendBufferSize(int size)
Sets the SO_SNDBUF option to the specified value for this DatagramSocket. The SO_SNDBUF option is used by the network implementation as a hint to size the underlying network I/O buffers. The SO_SNDBUF setting may also be used by the network implementation to determine the maximum size of the packet that can be sent on this socket.

As SO_SNDBUF is a hint, applications that want to verify what size the buffer is should call {@link #getSendBufferSize()}.

Increasing the buffer size may allow multiple outgoing packets to be queued by the network implementation when the send rate is high.

Note: If {@link #send(DatagramPacket)} is used to send a DatagramPacket that is larger than the setting of SO_SNDBUF then it is implementation specific if the packet is sent or discarded.

param
size the size to which to set the send buffer size. This value must be greater than 0.
exception
SocketException if there is an error in the underlying protocol, such as an UDP error.
exception
IllegalArgumentException if the value is 0 or is negative.
see
#getSendBufferSize()

	if (!(size > 0)) {
	    throw new IllegalArgumentException("negative send size");
	}
	if (isClosed())
	    throw new SocketException("Socket is closed");
	getImpl().setOption(SocketOptions.SO_SNDBUF, new Integer(size));
    
public synchronized voidsetSoTimeout(int timeout)
Enable/disable SO_TIMEOUT with the specified timeout, in milliseconds. With this option set to a non-zero timeout, a call to receive() for this DatagramSocket will block for only this amount of time. If the timeout expires, a java.net.SocketTimeoutException is raised, though the DatagramSocket is still valid. The option must be enabled prior to entering the blocking operation to have effect. The timeout must be > 0. A timeout of zero is interpreted as an infinite timeout.

param
timeout the specified timeout in milliseconds.
throws
SocketException if there is an error in the underlying protocol, such as an UDP error.
since
JDK1.1
see
#getSoTimeout()

	if (isClosed())
	    throw new SocketException("Socket is closed");
	getImpl().setOption(SocketOptions.SO_TIMEOUT, new Integer(timeout));
    
public synchronized voidsetTrafficClass(int tc)
Sets traffic class or type-of-service octet in the IP datagram header for datagrams sent from this DatagramSocket. As the underlying network implementation may ignore this value applications should consider it a hint.

The tc must be in the range 0 <= tc <= 255 or an IllegalArgumentException will be thrown.

Notes:

for Internet Protocol v4 the value consists of an octet with precedence and TOS fields as detailed in RFC 1349. The TOS field is bitset created by bitwise-or'ing values such the following :-

  • IPTOS_LOWCOST (0x02)
  • IPTOS_RELIABILITY (0x04)
  • IPTOS_THROUGHPUT (0x08)
  • IPTOS_LOWDELAY (0x10)
The last low order bit is always ignored as this corresponds to the MBZ (must be zero) bit.

Setting bits in the precedence field may result in a SocketException indicating that the operation is not permitted.

for Internet Protocol v6 tc is the value that would be placed into the sin6_flowinfo field of the IP header.

param
tc an int value for the bitset.
throws
SocketException if there is an error setting the traffic class or type-of-service
since
1.4
see
#getTrafficClass

	if (tc < 0 || tc > 255)
	    throw new IllegalArgumentException("tc is not in range 0 -- 255");

	if (isClosed())
	    throw new SocketException("Socket is closed");
        getImpl().setOption(SocketOptions.IP_TOS, new Integer(tc));