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Socket.javaAPI DocJava SE 6 API56101Tue Jun 10 00:25:42 BST 2008java.net

Socket

public class Socket extends Object
This class implements client sockets (also called just "sockets"). A socket is an endpoint for communication between two machines.

The actual work of the socket is performed by an instance of the SocketImpl class. An application, by changing the socket factory that creates the socket implementation, can configure itself to create sockets appropriate to the local firewall.

author
unascribed
version
1.115, 09/05/07
see
java.net.Socket#setSocketImplFactory(java.net.SocketImplFactory)
see
java.net.SocketImpl
see
java.nio.channels.SocketChannel
since
JDK1.0

Fields Summary
private boolean
created
Various states of this socket.
private boolean
bound
private boolean
connected
private boolean
closed
private Object
closeLock
private boolean
shutIn
private boolean
shutOut
SocketImpl
impl
The implementation of this Socket.
private boolean
oldImpl
Are we using an older SocketImpl?
private static SocketImplFactory
factory
The factory for all client sockets.
Constructors Summary
public Socket()
Creates an unconnected socket, with the system-default type of SocketImpl.

since
JDK1.1
revised
1.4


                         
      
	setImpl();
    
private Socket(SocketAddress address, SocketAddress localAddr, boolean stream)

	setImpl();

	// backward compatibility
	if (address == null)
	    throw new NullPointerException();

	try {
	    createImpl(stream);
	    if (localAddr != null)
		bind(localAddr);
	    if (address != null)
		connect(address);
	} catch (IOException e) {
	    close();
	    throw e;
	}
    
public Socket(Proxy proxy)
Creates an unconnected socket, specifying the type of proxy, if any, that should be used regardless of any other settings.

If there is a security manager, its checkConnect method is called with the proxy host address and port number as its arguments. This could result in a SecurityException.

Examples:

  • Socket s = new Socket(Proxy.NO_PROXY); will create a plain socket ignoring any other proxy configuration.
  • Socket s = new Socket(new Proxy(Proxy.Type.SOCKS, new InetSocketAddress("socks.mydom.com", 1080))); will create a socket connecting through the specified SOCKS proxy server.

param
proxy a {@link java.net.Proxy Proxy} object specifying what kind of proxying should be used.
throws
IllegalArgumentException if the proxy is of an invalid type or null.
throws
SecurityException if a security manager is present and permission to connect to the proxy is denied.
see
java.net.ProxySelector
see
java.net.Proxy
since
1.5

	if (proxy != null && proxy.type() == Proxy.Type.SOCKS) {
	    SecurityManager security = System.getSecurityManager();
	    InetSocketAddress epoint = (InetSocketAddress) proxy.address();
	    if (security != null) {
		if (epoint.isUnresolved())
		    epoint = new InetSocketAddress(epoint.getHostName(), epoint.getPort());
		if (epoint.isUnresolved())
		    security.checkConnect(epoint.getHostName(), epoint.getPort());
		else
		    security.checkConnect(epoint.getAddress().getHostAddress(),
					  epoint.getPort());
	    }
	    impl = new SocksSocketImpl(proxy);
	    impl.setSocket(this);
	} else {
	    if (proxy == Proxy.NO_PROXY) {
		if (factory == null) {
		    impl = new PlainSocketImpl();
		    impl.setSocket(this);
		} else
		    setImpl();
	    } else
		throw new IllegalArgumentException("Invalid Proxy");
	}
    
protected Socket(SocketImpl impl)
Creates an unconnected Socket with a user-specified SocketImpl.

param
impl an instance of a SocketImpl the subclass wishes to use on the Socket.
exception
SocketException if there is an error in the underlying protocol, such as a TCP error.
since
JDK1.1

	this.impl = impl;
	if (impl != null) {
	    checkOldImpl();
	    this.impl.setSocket(this);
	}
    
public Socket(String host, int port)
Creates a stream socket and connects it to the specified port number on the named host.

If the specified host is null it is the equivalent of specifying the address as {@link java.net.InetAddress#getByName InetAddress.getByName}(null). In other words, it is equivalent to specifying an address of the loopback interface.

If the application has specified a server socket factory, that factory's createSocketImpl method is called to create the actual socket implementation. Otherwise a "plain" socket is created.

If there is a security manager, its checkConnect method is called with the host address and port as its arguments. This could result in a SecurityException.

param
host the host name, or null for the loopback address.
param
port the port number.
exception
UnknownHostException if the IP address of the host could not be determined.
exception
IOException if an I/O error occurs when creating the socket.
exception
SecurityException if a security manager exists and its checkConnect method doesn't allow the operation.
see
java.net.Socket#setSocketImplFactory(java.net.SocketImplFactory)
see
java.net.SocketImpl
see
java.net.SocketImplFactory#createSocketImpl()
see
SecurityManager#checkConnect

	this(host != null ? new InetSocketAddress(host, port) :
	     new InetSocketAddress(InetAddress.getByName(null), port),
	     (SocketAddress) null, true);
    
public Socket(InetAddress address, int port)
Creates a stream socket and connects it to the specified port number at the specified IP address.

If the application has specified a socket factory, that factory's createSocketImpl method is called to create the actual socket implementation. Otherwise a "plain" socket is created.

If there is a security manager, its checkConnect method is called with the host address and port as its arguments. This could result in a SecurityException.

param
address the IP address.
param
port the port number.
exception
IOException if an I/O error occurs when creating the socket.
exception
SecurityException if a security manager exists and its checkConnect method doesn't allow the operation.
see
java.net.Socket#setSocketImplFactory(java.net.SocketImplFactory)
see
java.net.SocketImpl
see
java.net.SocketImplFactory#createSocketImpl()
see
SecurityManager#checkConnect

	this(address != null ? new InetSocketAddress(address, port) : null, 
	     (SocketAddress) null, true);
    
public Socket(String host, int port, InetAddress localAddr, int localPort)
Creates a socket and connects it to the specified remote host on the specified remote port. The Socket will also bind() to the local address and port supplied.

If the specified host is null it is the equivalent of specifying the address as {@link java.net.InetAddress#getByName InetAddress.getByName}(null). In other words, it is equivalent to specifying an address of the loopback interface.

If there is a security manager, its checkConnect method is called with the host address and port as its arguments. This could result in a SecurityException.

param
host the name of the remote host, or null for the loopback address.
param
port the remote port
param
localAddr the local address the socket is bound to
param
localPort the local port the socket is bound to
exception
IOException if an I/O error occurs when creating the socket.
exception
SecurityException if a security manager exists and its checkConnect method doesn't allow the operation.
see
SecurityManager#checkConnect
since
JDK1.1

	this(host != null ? new InetSocketAddress(host, port) :
	       new InetSocketAddress(InetAddress.getByName(null), port),
	     new InetSocketAddress(localAddr, localPort), true);
    
public Socket(InetAddress address, int port, InetAddress localAddr, int localPort)
Creates a socket and connects it to the specified remote address on the specified remote port. The Socket will also bind() to the local address and port supplied.

If there is a security manager, its checkConnect method is called with the host address and port as its arguments. This could result in a SecurityException.

param
address the remote address
param
port the remote port
param
localAddr the local address the socket is bound to
param
localPort the local port the socket is bound to
exception
IOException if an I/O error occurs when creating the socket.
exception
SecurityException if a security manager exists and its checkConnect method doesn't allow the operation.
see
SecurityManager#checkConnect
since
JDK1.1

	this(address != null ? new InetSocketAddress(address, port) : null,
	     new InetSocketAddress(localAddr, localPort), true);
    
public Socket(String host, int port, boolean stream)
Creates a stream socket and connects it to the specified port number on the named host.

If the specified host is null it is the equivalent of specifying the address as {@link java.net.InetAddress#getByName InetAddress.getByName}(null). In other words, it is equivalent to specifying an address of the loopback interface.

If the stream argument is true, this creates a stream socket. If the stream argument is false, it creates a datagram socket.

If the application has specified a server socket factory, that factory's createSocketImpl method is called to create the actual socket implementation. Otherwise a "plain" socket is created.

If there is a security manager, its checkConnect method is called with the host address and port as its arguments. This could result in a SecurityException.

If a UDP socket is used, TCP/IP related socket options will not apply.

param
host the host name, or null for the loopback address.
param
port the port number.
param
stream a boolean indicating whether this is a stream socket or a datagram socket.
exception
IOException if an I/O error occurs when creating the socket.
exception
SecurityException if a security manager exists and its checkConnect method doesn't allow the operation.
see
java.net.Socket#setSocketImplFactory(java.net.SocketImplFactory)
see
java.net.SocketImpl
see
java.net.SocketImplFactory#createSocketImpl()
see
SecurityManager#checkConnect
deprecated
Use DatagramSocket instead for UDP transport.

	this(host != null ? new InetSocketAddress(host, port) :
	       new InetSocketAddress(InetAddress.getByName(null), port),
	     (SocketAddress) null, stream);
    
public Socket(InetAddress host, int port, boolean stream)
Creates a socket and connects it to the specified port number at the specified IP address.

If the stream argument is true, this creates a stream socket. If the stream argument is false, it creates a datagram socket.

If the application has specified a server socket factory, that factory's createSocketImpl method is called to create the actual socket implementation. Otherwise a "plain" socket is created.

If there is a security manager, its checkConnect method is called with host.getHostAddress() and port as its arguments. This could result in a SecurityException.

If UDP socket is used, TCP/IP related socket options will not apply.

param
host the IP address.
param
port the port number.
param
stream if true, create a stream socket; otherwise, create a datagram socket.
exception
IOException if an I/O error occurs when creating the socket.
exception
SecurityException if a security manager exists and its checkConnect method doesn't allow the operation.
see
java.net.Socket#setSocketImplFactory(java.net.SocketImplFactory)
see
java.net.SocketImpl
see
java.net.SocketImplFactory#createSocketImpl()
see
SecurityManager#checkConnect
deprecated
Use DatagramSocket instead for UDP transport.

	this(host != null ? new InetSocketAddress(host, port) : null, 
	     new InetSocketAddress(0), stream);
    
Methods Summary
public voidbind(java.net.SocketAddress bindpoint)
Binds the socket to a local address.

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

param
bindpoint the SocketAddress to bind to
throws
IOException if the bind operation fails, or if the socket is already bound.
throws
IllegalArgumentException if bindpoint is a SocketAddress subclass not supported by this socket
since
1.4
see
#isBound

	if (isClosed())
	    throw new SocketException("Socket is closed");
	if (!oldImpl && isBound())
	    throw new SocketException("Already bound");

	if (bindpoint != null && (!(bindpoint instanceof InetSocketAddress)))
	    throw new IllegalArgumentException("Unsupported address type");
	InetSocketAddress epoint = (InetSocketAddress) bindpoint;
	if (epoint != null && epoint.isUnresolved())
	    throw new SocketException("Unresolved address");
	if (bindpoint == null)
	    getImpl().bind(InetAddress.anyLocalAddress(), 0);
	else
	    getImpl().bind(epoint.getAddress(),
			   epoint.getPort());
	bound = true;
    
private voidcheckOldImpl()

	if (impl == null)
	    return;
	// SocketImpl.connect() is a protected method, therefore we need to use
	// getDeclaredMethod, therefore we need permission to access the member

        oldImpl = AccessController.doPrivileged
				(new PrivilegedAction<Boolean>() {
	    public Boolean run() {
	        Class[] cl = new Class[2];
	        cl[0] = SocketAddress.class;
	        cl[1] = Integer.TYPE;
	        Class clazz = impl.getClass();
	        while (true) {
		    try {
		        clazz.getDeclaredMethod("connect", cl);
		        return Boolean.FALSE;
		    } catch (NoSuchMethodException e) {
		        clazz = clazz.getSuperclass();
			// java.net.SocketImpl class will always have this abstract method.
			// If we have not found it by now in the hierarchy then it does not
			// exist, we are an old style impl.
			if (clazz.equals(java.net.SocketImpl.class)) {
                            return Boolean.TRUE;
                        }
		    }
	        }
	    }
        });
    
public synchronized voidclose()
Closes this socket.

Any thread currently blocked in an I/O operation upon this socket will throw a {@link SocketException}.

Once a socket has been closed, it is not available for further networking use (i.e. can't be reconnected or rebound). A new socket needs to be created.

Closing this socket will also close the socket's {@link java.io.InputStream InputStream} and {@link java.io.OutputStream OutputStream}.

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

exception
IOException if an I/O error occurs when closing this socket.
revised
1.4
spec
JSR-51
see
#isClosed

	synchronized(closeLock) {
	    if (isClosed())
		return;
	    if (created)
		impl.close();
	    closed = true;
	}
    
public voidconnect(java.net.SocketAddress endpoint)
Connects this socket to the server.

param
endpoint the SocketAddress
throws
IOException if an error occurs during the connection
throws
java.nio.channels.IllegalBlockingModeException if this socket has an associated channel, and the channel is in non-blocking mode
throws
IllegalArgumentException if endpoint is null or is a SocketAddress subclass not supported by this socket
since
1.4
spec
JSR-51

	connect(endpoint, 0);
    
public voidconnect(java.net.SocketAddress endpoint, int timeout)
Connects this socket to the server with a specified timeout value. A timeout of zero is interpreted as an infinite timeout. The connection will then block until established or an error occurs.

param
endpoint the SocketAddress
param
timeout the timeout value to be used in milliseconds.
throws
IOException if an error occurs during the connection
throws
SocketTimeoutException if timeout expires before connecting
throws
java.nio.channels.IllegalBlockingModeException if this socket has an associated channel, and the channel is in non-blocking mode
throws
IllegalArgumentException if endpoint is null or is a SocketAddress subclass not supported by this socket
since
1.4
spec
JSR-51

	if (endpoint == null)
	    throw new IllegalArgumentException("connect: The address can't be null");

	if (timeout < 0)
	  throw new IllegalArgumentException("connect: timeout can't be negative");

	if (isClosed())
	    throw new SocketException("Socket is closed");

	if (!oldImpl && isConnected())
	    throw new SocketException("already connected");

	if (!(endpoint instanceof InetSocketAddress))
	    throw new IllegalArgumentException("Unsupported address type");

	InetSocketAddress epoint = (InetSocketAddress) endpoint;

	SecurityManager security = System.getSecurityManager();
	if (security != null) {
	    if (epoint.isUnresolved())
		security.checkConnect(epoint.getHostName(),
				      epoint.getPort());
	    else
		security.checkConnect(epoint.getAddress().getHostAddress(),
				      epoint.getPort());
	}
	if (!created)
	    createImpl(true);
	if (!oldImpl)
	    impl.connect(epoint, timeout);
	else if (timeout == 0) {
	    if (epoint.isUnresolved())
		impl.connect(epoint.getAddress().getHostName(),
			     epoint.getPort());
	    else
		impl.connect(epoint.getAddress(), epoint.getPort());
	} else
	    throw new UnsupportedOperationException("SocketImpl.connect(addr, timeout)");
	connected = true;
	/*
	 * If the socket was not bound before the connect, it is now because
	 * the kernel will have picked an ephemeral port & a local address
	 */
	bound = true;
    
voidcreateImpl(boolean stream)
Creates the socket implementation.

param
stream a boolean value : true for a TCP socket, false for UDP.
throws
IOException if creation fails
since
1.4

	if (impl == null) 
	    setImpl();
	try {
	    impl.create(stream);
	    created = true;
	} catch (IOException e) {
	    throw new SocketException(e.getMessage());
	}
    
public java.nio.channels.SocketChannelgetChannel()
Returns the unique {@link java.nio.channels.SocketChannel SocketChannel} object associated with this socket, if any.

A socket will have a channel if, and only if, the channel itself was created via the {@link java.nio.channels.SocketChannel#open SocketChannel.open} or {@link java.nio.channels.ServerSocketChannel#accept ServerSocketChannel.accept} methods.

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

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

return
the SocketImpl attached to that ServerSocket.
throws
SocketException if creation fails
since
1.4

	if (!created)
	    createImpl(true);
	return impl;
    
public java.net.InetAddressgetInetAddress()
Returns the address to which the socket is connected.

return
the remote IP address to which this socket is connected, or null if the socket is not connected.

	if (!isConnected())
	    return null;
	try {
	    return getImpl().getInetAddress();
	} catch (SocketException e) {
	}
	return null;
    
public java.io.InputStreamgetInputStream()
Returns an input stream for this socket.

If this socket has an associated channel then the resulting input stream delegates all of its operations to the channel. If the channel is in non-blocking mode then the input stream's read operations will throw an {@link java.nio.channels.IllegalBlockingModeException}.

Under abnormal conditions the underlying connection may be broken by the remote host or the network software (for example a connection reset in the case of TCP connections). When a broken connection is detected by the network software the following applies to the returned input stream :-

  • The network software may discard bytes that are buffered by the socket. Bytes that aren't discarded by the network software can be read using {@link java.io.InputStream#read read}.

  • If there are no bytes buffered on the socket, or all buffered bytes have been consumed by {@link java.io.InputStream#read read}, then all subsequent calls to {@link java.io.InputStream#read read} will throw an {@link java.io.IOException IOException}.

  • If there are no bytes buffered on the socket, and the socket has not been closed using {@link #close close}, then {@link java.io.InputStream#available available} will return 0.

Closing the returned {@link java.io.InputStream InputStream} will close the associated socket.

return
an input stream for reading bytes from this socket.
exception
IOException if an I/O error occurs when creating the input stream, the socket is closed, the socket is not connected, or the socket input has been shutdown using {@link #shutdownInput()}
revised
1.4
spec
JSR-51

	if (isClosed())
	    throw new SocketException("Socket is closed");
	if (!isConnected())
	    throw new SocketException("Socket is not connected");
	if (isInputShutdown())
	    throw new SocketException("Socket input is shutdown");
	final Socket s = this;
	InputStream is = null;
	try {
	    is = (InputStream)
		AccessController.doPrivileged(new PrivilegedExceptionAction() {
		    public Object run() throws IOException {
			return impl.getInputStream();
		    }
		});
	} catch (java.security.PrivilegedActionException e) {
	    throw (IOException) e.getException();
	}
	return is;
    
public booleangetKeepAlive()
Tests if SO_KEEPALIVE is enabled.

return
a boolean indicating whether or not SO_KEEPALIVE is enabled.
exception
SocketException if there is an error in the underlying protocol, such as a TCP error.
since
1.3
see
#setKeepAlive(boolean)

	if (isClosed())
	    throw new SocketException("Socket is closed");
	return ((Boolean) getImpl().getOption(SocketOptions.SO_KEEPALIVE)).booleanValue();
    
public java.net.InetAddressgetLocalAddress()
Gets the local address to which the socket is bound.

return
the local address to which the socket is bound or InetAddress.anyLocalAddress() if the socket is not bound yet.
since
JDK1.1

	// This is for backward compatibility
	if (!isBound())
	    return InetAddress.anyLocalAddress();
	InetAddress in = null;
	try {
	    in = (InetAddress) getImpl().getOption(SocketOptions.SO_BINDADDR);
	    if (in.isAnyLocalAddress()) {
		in = InetAddress.anyLocalAddress();
	    }
	} catch (Exception e) {
	    in = InetAddress.anyLocalAddress(); // "0.0.0.0"
	}
	return in;
    
public intgetLocalPort()
Returns the local port to which this socket is bound.

return
the local port number to which this socket is bound or -1 if the socket is not bound yet.

	if (!isBound())
	    return -1;
	try {
	    return getImpl().getLocalPort();
	} catch(SocketException e) {
	    // shouldn't happen as we're bound
	}
	return -1;
    
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 booleangetOOBInline()
Tests if OOBINLINE is enabled.

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

	if (isClosed())
	    throw new SocketException("Socket is closed");
	return ((Boolean) getImpl().getOption(SocketOptions.SO_OOBINLINE)).booleanValue();
    
public java.io.OutputStreamgetOutputStream()
Returns an output stream for this socket.

If this socket has an associated channel then the resulting output stream delegates all of its operations to the channel. If the channel is in non-blocking mode then the output stream's write operations will throw an {@link java.nio.channels.IllegalBlockingModeException}.

Closing the returned {@link java.io.OutputStream OutputStream} will close the associated socket.

return
an output stream for writing bytes to this socket.
exception
IOException if an I/O error occurs when creating the output stream or if the socket is not connected.
revised
1.4
spec
JSR-51

	if (isClosed())
	    throw new SocketException("Socket is closed");
	if (!isConnected())
	    throw new SocketException("Socket is not connected");
	if (isOutputShutdown())
	    throw new SocketException("Socket output is shutdown");
	final Socket s = this;
	OutputStream os = null;
	try {
	    os = (OutputStream)
		AccessController.doPrivileged(new PrivilegedExceptionAction() {
		    public Object run() throws IOException {
			return impl.getOutputStream();
		    }
		});
	} catch (java.security.PrivilegedActionException e) {
	    throw (IOException) e.getException();
	}
	return os;
    
public intgetPort()
Returns the remote port to which this socket is connected.

return
the remote port number to which this socket is connected, or 0 if the socket is not connected yet.

	if (!isConnected())
	    return 0;
	try {
	    return getImpl().getPort();
	} catch (SocketException e) {
	    // Shouldn't happen as we're connected
	}
	return -1;
    
public synchronized intgetReceiveBufferSize()
Gets the value of the SO_RCVBUF option for this Socket, that is the buffer size used by the platform for input on this Socket.

return
the value of the SO_RCVBUF option for this Socket.
exception
SocketException if there is an error in the underlying protocol, such as a TCP error.
see
#setReceiveBufferSize(int)
since
1.2

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

	if (!isConnected())
	    return null;
	return new InetSocketAddress(getInetAddress(), getPort());
    
public 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 a TCP error.
since
1.4
see
#setReuseAddress(boolean)

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

return
the value of the SO_SNDBUF option for this Socket.
exception
SocketException if there is an error in the underlying protocol, such as a TCP error.
see
#setSendBufferSize(int)
since
1.2

	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 intgetSoLinger()
Returns setting for SO_LINGER. -1 returns implies that the option is disabled. The setting only affects socket close.

return
the setting for SO_LINGER.
exception
SocketException if there is an error in the underlying protocol, such as a TCP error.
since
JDK1.1
see
#setSoLinger(boolean, int)

	if (isClosed())
	    throw new SocketException("Socket is closed");
	Object o = getImpl().getOption(SocketOptions.SO_LINGER);
	if (o instanceof Integer) {
	    return ((Integer) o).intValue();
	} else {
	    return -1;
	}
    
public synchronized intgetSoTimeout()
Returns setting for SO_TIMEOUT. 0 returns implies that the option is disabled (i.e., timeout of infinity).

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

	if (isClosed())
	    throw new SocketException("Socket is closed");
	Object o = getImpl().getOption(SocketOptions.SO_TIMEOUT);
	/* extra type safety */
	if (o instanceof Integer) {
	    return ((Integer) o).intValue();
	} else {
	    return 0;
	}
    
public booleangetTcpNoDelay()
Tests if TCP_NODELAY is enabled.

return
a boolean indicating whether or not TCP_NODELAY is enabled.
exception
SocketException if there is an error in the underlying protocol, such as a TCP error.
since
JDK1.1
see
#setTcpNoDelay(boolean)

	if (isClosed())
	    throw new SocketException("Socket is closed");
	return ((Boolean) getImpl().getOption(SocketOptions.TCP_NODELAY)).booleanValue();
    
public intgetTrafficClass()
Gets traffic class or type-of-service in the IP header for packets sent from this Socket

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 Socket.

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)

        return ((Integer) (getImpl().getOption(SocketOptions.IP_TOS))).intValue();
    
public booleanisBound()
Returns the binding state of the socket.

return
true if the socket successfuly bound to an address
since
1.4
see
#bind

	// Before 1.3 Sockets were always bound during creation
	return bound || oldImpl;
    
public booleanisClosed()
Returns the closed state of the socket.

return
true if the socket has been closed
since
1.4
see
#close

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

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

	// Before 1.3 Sockets were always connected during creation
	return connected || oldImpl;
    
public booleanisInputShutdown()
Returns whether the read-half of the socket connection is closed.

return
true if the input of the socket has been shutdown
since
1.4
see
#shutdownInput

	return shutIn;
    
public booleanisOutputShutdown()
Returns whether the write-half of the socket connection is closed.

return
true if the output of the socket has been shutdown
since
1.4
see
#shutdownOutput

	return shutOut;
    
final voidpostAccept()
set the flags after an accept() call.

 
	connected = true;
	created = true;
	bound = true;
    
public voidsendUrgentData(int data)
Send one byte of urgent data on the socket. The byte to be sent is the lowest eight bits of the data parameter. The urgent byte is sent after any preceding writes to the socket OutputStream and before any future writes to the OutputStream.

param
data The byte of data to send
exception
IOException if there is an error sending the data.
since
1.4

        if (!getImpl().supportsUrgentData ()) {
            throw new SocketException ("Urgent data not supported");
        }
        getImpl().sendUrgentData (data);
    
voidsetBound()

	bound = true;
    
voidsetConnected()

	connected = true;
    
voidsetCreated()

	created = true;
    
voidsetImpl()
Sets impl to the system-default type of SocketImpl.

since
1.4

	if (factory != null) {
	    impl = factory.createSocketImpl();
	    checkOldImpl();
	} else {
	    // No need to do a checkOldImpl() here, we know it's an up to date
	    // SocketImpl!
	    impl = new SocksSocketImpl();
	}
	if (impl != null)
	    impl.setSocket(this);
    
public voidsetKeepAlive(boolean on)
Enable/disable SO_KEEPALIVE.

param
on whether or not to have socket keep alive turned on.
exception
SocketException if there is an error in the underlying protocol, such as a TCP error.
since
1.3
see
#getKeepAlive()

	if (isClosed())
	    throw new SocketException("Socket is closed");
        getImpl().setOption(SocketOptions.SO_KEEPALIVE, Boolean.valueOf(on));
    
public voidsetOOBInline(boolean on)
Enable/disable OOBINLINE (receipt of TCP urgent data) By default, this option is disabled and TCP urgent data received on a socket is silently discarded. If the user wishes to receive urgent data, then this option must be enabled. When enabled, urgent data is received inline with normal data.

Note, only limited support is provided for handling incoming urgent data. In particular, no notification of incoming urgent data is provided and there is no capability to distinguish between normal data and urgent data unless provided by a higher level protocol.

param
on true to enable OOBINLINE, false to disable.
exception
SocketException if there is an error in the underlying protocol, such as a TCP error.
since
1.4
see
#getOOBInline()

	if (isClosed())
	    throw new SocketException("Socket is closed");
	getImpl().setOption(SocketOptions.SO_OOBINLINE, Boolean.valueOf(on));
    
public voidsetPerformancePreferences(int connectionTime, int latency, int bandwidth)
Sets performance preferences for this socket.

Sockets use the TCP/IP protocol by default. Some implementations may offer alternative protocols which have different performance characteristics than TCP/IP. This method allows the application to express its own preferences as to how these tradeoffs should be made when the implementation chooses from the available protocols.

Performance preferences are described by three integers whose values indicate the relative importance of short connection time, low latency, and high bandwidth. The absolute values of the integers are irrelevant; in order to choose a protocol the values are simply compared, with larger values indicating stronger preferences. Negative values represent a lower priority than positive values. If the application prefers short connection time over both low latency and high bandwidth, for example, then it could invoke this method with the values (1, 0, 0). If the application prefers high bandwidth above low latency, and low latency above short connection time, then it could invoke this method with the values (0, 1, 2).

Invoking this method after this socket has been connected will have no effect.

param
connectionTime An int expressing the relative importance of a short connection time
param
latency An int expressing the relative importance of low latency
param
bandwidth An int expressing the relative importance of high bandwidth
since
1.5

	/* Not implemented yet */
    
public synchronized voidsetReceiveBufferSize(int size)
Sets the SO_RCVBUF option to the specified value for this Socket. The SO_RCVBUF option is used by the platform's networking code as a hint for the size to set the underlying network I/O buffers.

Increasing the receive buffer size can increase the performance of network I/O for high-volume connection, while decreasing it can help reduce the backlog of incoming data.

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

The value of SO_RCVBUF is also used to set the TCP receive window that is advertized to the remote peer. Generally, the window size can be modified at any time when a socket is connected. However, if a receive window larger than 64K is required then this must be requested before the socket is connected to the remote peer. There are two cases to be aware of:

  1. For sockets accepted from a ServerSocket, this must be done by calling {@link ServerSocket#setReceiveBufferSize(int)} before the ServerSocket is bound to a local address.

  2. For client sockets, setReceiveBufferSize() must be called before connecting the socket to its remote peer.

param
size the size to which to set the receive buffer size. This value must be greater than 0.
exception
IllegalArgumentException if the value is 0 or is negative.
exception
SocketException if there is an error in the underlying protocol, such as a TCP error.
see
#getReceiveBufferSize()
see
ServerSocket#setReceiveBufferSize(int)
since
1.2

	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 voidsetReuseAddress(boolean on)
Enable/disable the SO_REUSEADDR socket option.

When a TCP connection is closed the connection may remain in a timeout state for a period of time after the connection is closed (typically known as the TIME_WAIT state or 2MSL wait state). For applications using a well known socket address or port it may not be possible to bind a socket to the required SocketAddress if there is a connection in the timeout state involving the socket address or port.

Enabling SO_REUSEADDR prior to binding the socket using {@link #bind(SocketAddress)} allows the socket to be bound even though a previous connection is in a timeout state.

When a Socket 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 socket option
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
#isClosed()
see
#isBound()

	if (isClosed())
	    throw new SocketException("Socket is closed");
        getImpl().setOption(SocketOptions.SO_REUSEADDR, Boolean.valueOf(on));
    
public synchronized voidsetSendBufferSize(int size)
Sets the SO_SNDBUF option to the specified value for this Socket. The SO_SNDBUF option is used by the platform's networking code as a hint for the size to set the underlying network I/O buffers.

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

exception
SocketException if there is an error in the underlying protocol, such as a TCP error.
param
size the size to which to set the send buffer size. This value must be greater than 0.
exception
IllegalArgumentException if the value is 0 or is negative.
see
#getSendBufferSize()
since
1.2

	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 voidsetSoLinger(boolean on, int linger)
Enable/disable SO_LINGER with the specified linger time in seconds. The maximum timeout value is platform specific. The setting only affects socket close.

param
on whether or not to linger on.
param
linger how long to linger for, if on is true.
exception
SocketException if there is an error in the underlying protocol, such as a TCP error.
exception
IllegalArgumentException if the linger value is negative.
since
JDK1.1
see
#getSoLinger()

	if (isClosed())
	    throw new SocketException("Socket is closed");
	if (!on) {
	    getImpl().setOption(SocketOptions.SO_LINGER, new Boolean(on));
	} else {
	    if (linger < 0) {
		throw new IllegalArgumentException("invalid value for SO_LINGER");
	    }
            if (linger > 65535)
                linger = 65535;
	    getImpl().setOption(SocketOptions.SO_LINGER, new Integer(linger));
	}
    
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 read() call on the InputStream associated with this Socket will block for only this amount of time. If the timeout expires, a java.net.SocketTimeoutException is raised, though the Socket 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.
exception
SocketException if there is an error in the underlying protocol, such as a TCP error.
since
JDK 1.1
see
#getSoTimeout()

	if (isClosed())
	    throw new SocketException("Socket is closed");
	if (timeout < 0)
	  throw new IllegalArgumentException("timeout can't be negative");

	getImpl().setOption(SocketOptions.SO_TIMEOUT, new Integer(timeout));
    
public static synchronized voidsetSocketImplFactory(java.net.SocketImplFactory fac)
Sets the client socket implementation factory for the application. The factory can be specified only once.

When an application creates a new client socket, the socket implementation factory's createSocketImpl method is called to create the actual 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 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.SocketImplFactory#createSocketImpl()
see
SecurityManager#checkSetFactory


                                                                                                                                                                                               
         
	 
    
	if (factory != null) {
	    throw new SocketException("factory already defined");
	}
	SecurityManager security = System.getSecurityManager();
	if (security != null) {
	    security.checkSetFactory();
	}
	factory = fac;
    
public voidsetTcpNoDelay(boolean on)
Enable/disable TCP_NODELAY (disable/enable Nagle's algorithm).

param
on true to enable TCP_NODELAY, false to disable.
exception
SocketException if there is an error in the underlying protocol, such as a TCP error.
since
JDK1.1
see
#getTcpNoDelay()

	if (isClosed())
	    throw new SocketException("Socket is closed");
	getImpl().setOption(SocketOptions.TCP_NODELAY, Boolean.valueOf(on));
    
public voidsetTrafficClass(int tc)
Sets traffic class or type-of-service octet in the IP header for packets sent from this Socket. 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.

As RFC 1122 section 4.2.4.2 indicates, a compliant TCP implementation should, but is not required to, let application change the TOS field during the lifetime of a connection. So whether the type-of-service field can be changed after the TCP connection has been established depends on the implementation in the underlying platform. Applications should not assume that they can change the TOS field after the connection.

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));
    
public voidshutdownInput()
Places the input stream for this socket at "end of stream". Any data sent to the input stream side of the socket is acknowledged and then silently discarded.

If you read from a socket input stream after invoking shutdownInput() on the socket, the stream will return EOF.

exception
IOException if an I/O error occurs when shutting down this socket.
since
1.3
see
java.net.Socket#shutdownOutput()
see
java.net.Socket#close()
see
java.net.Socket#setSoLinger(boolean, int)
see
#isInputShutdown

	if (isClosed())
	    throw new SocketException("Socket is closed");
	if (!isConnected())
	    throw new SocketException("Socket is not connected");
	if (isInputShutdown())
	    throw new SocketException("Socket input is already shutdown");
	getImpl().shutdownInput();
	shutIn = true;
    
public voidshutdownOutput()
Disables the output stream for this socket. For a TCP socket, any previously written data will be sent followed by TCP's normal connection termination sequence. If you write to a socket output stream after invoking shutdownOutput() on the socket, the stream will throw an IOException.

exception
IOException if an I/O error occurs when shutting down this socket.
since
1.3
see
java.net.Socket#shutdownInput()
see
java.net.Socket#close()
see
java.net.Socket#setSoLinger(boolean, int)
see
#isOutputShutdown

	if (isClosed())
	    throw new SocketException("Socket is closed");
	if (!isConnected())
	    throw new SocketException("Socket is not connected");
	if (isOutputShutdown())
	    throw new SocketException("Socket output is already shutdown");
	getImpl().shutdownOutput();
	shutOut = true;
    
public java.lang.StringtoString()
Converts this socket to a String.

return
a string representation of this socket.

	try {
	    if (isConnected())
		return "Socket[addr=" + getImpl().getInetAddress() +
		    ",port=" + getImpl().getPort() +
		    ",localport=" + getImpl().getLocalPort() + "]";
	} catch (SocketException e) {
	}
	return "Socket[unconnected]";