Java example source code file (ServerSocket.java)
The ServerSocket.java Java example source code/*
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*
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*
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package java.net;
import java.io.FileDescriptor;
import java.io.IOException;
import java.nio.channels.ServerSocketChannel;
import java.security.AccessController;
import java.security.PrivilegedExceptionAction;
/**
* This class implements server sockets. A server socket waits for
* requests to come in over the network. It performs some operation
* based on that request, and then possibly returns a result to the requester.
* <p>
* The actual work of the server socket is performed by an instance
* of the {@code SocketImpl} class. An application can
* change the socket factory that creates the socket
* implementation to configure itself to create sockets
* appropriate to the local firewall.
*
* @author unascribed
* @see java.net.SocketImpl
* @see java.net.ServerSocket#setSocketFactory(java.net.SocketImplFactory)
* @see java.nio.channels.ServerSocketChannel
* @since JDK1.0
*/
public
class ServerSocket implements java.io.Closeable {
/**
* Various states of this socket.
*/
private boolean created = false;
private boolean bound = false;
private boolean closed = false;
private Object closeLock = new Object();
/**
* The implementation of this Socket.
*/
private SocketImpl impl;
/**
* Are we using an older SocketImpl?
*/
private boolean oldImpl = false;
/**
* Package-private constructor to create a ServerSocket associated with
* the given SocketImpl.
*/
ServerSocket(SocketImpl impl) {
this.impl = impl;
impl.setServerSocket(this);
}
/**
* Creates an unbound server socket.
*
* @exception IOException IO error when opening the socket.
* @revised 1.4
*/
public ServerSocket() throws IOException {
setImpl();
}
/**
* Creates a server socket, bound to the specified port. A port number
* of {@code 0} means that the port number is automatically
* allocated, typically from an ephemeral port range. This port
* number can then be retrieved by calling {@link #getLocalPort getLocalPort}.
* <p>
* The maximum queue length for incoming connection indications (a
* request to connect) is set to {@code 50}. If a connection
* indication arrives when the queue is full, the connection is refused.
* <p>
* If the application has specified a server socket factory, that
* factory's {@code createSocketImpl} method is called to create
* the actual socket implementation. Otherwise a "plain" socket is created.
* <p>
* If there is a security manager,
* its {@code checkListen} method is called
* with the {@code port} argument
* as its argument to ensure the operation is allowed.
* This could result in a SecurityException.
*
*
* @param port the port number, or {@code 0} to use a port
* number that is automatically allocated.
*
* @exception IOException if an I/O error occurs when opening the socket.
* @exception SecurityException
* if a security manager exists and its {@code checkListen}
* method doesn't allow the operation.
* @exception IllegalArgumentException if the port parameter is outside
* the specified range of valid port values, which is between
* 0 and 65535, inclusive.
*
* @see java.net.SocketImpl
* @see java.net.SocketImplFactory#createSocketImpl()
* @see java.net.ServerSocket#setSocketFactory(java.net.SocketImplFactory)
* @see SecurityManager#checkListen
*/
public ServerSocket(int port) throws IOException {
this(port, 50, null);
}
/**
* Creates a server socket and binds it to the specified local port
* number, with the specified backlog.
* A port number of {@code 0} means that the port number is
* automatically allocated, typically from an ephemeral port range.
* This port number can then be retrieved by calling
* {@link #getLocalPort getLocalPort}.
* <p>
* The maximum queue length for incoming connection indications (a
* request to connect) is set to the {@code backlog} parameter. If
* a connection indication arrives when the queue is full, the
* connection is refused.
* <p>
* If the application has specified a server socket factory, that
* factory's {@code createSocketImpl} method is called to create
* the actual socket implementation. Otherwise a "plain" socket is created.
* <p>
* If there is a security manager,
* its {@code checkListen} method is called
* with the {@code port} argument
* as its argument to ensure the operation is allowed.
* This could result in a SecurityException.
*
* The {@code backlog} argument is the requested maximum number of
* pending connections on the socket. Its exact semantics are implementation
* specific. In particular, an implementation may impose a maximum length
* or may choose to ignore the parameter altogther. The value provided
* should be greater than {@code 0}. If it is less than or equal to
* {@code 0}, then an implementation specific default will be used.
* <P>
*
* @param port the port number, or {@code 0} to use a port
* number that is automatically allocated.
* @param backlog requested maximum length of the queue of incoming
* connections.
*
* @exception IOException if an I/O error occurs when opening the socket.
* @exception SecurityException
* if a security manager exists and its {@code checkListen}
* method doesn't allow the operation.
* @exception IllegalArgumentException if the port parameter is outside
* the specified range of valid port values, which is between
* 0 and 65535, inclusive.
*
* @see java.net.SocketImpl
* @see java.net.SocketImplFactory#createSocketImpl()
* @see java.net.ServerSocket#setSocketFactory(java.net.SocketImplFactory)
* @see SecurityManager#checkListen
*/
public ServerSocket(int port, int backlog) throws IOException {
this(port, backlog, null);
}
/**
* Create a server with the specified port, listen backlog, and
* local IP address to bind to. The <i>bindAddr argument
* can be used on a multi-homed host for a ServerSocket that
* will only accept connect requests to one of its addresses.
* If <i>bindAddr is null, it will default accepting
* connections on any/all local addresses.
* The port must be between 0 and 65535, inclusive.
* A port number of {@code 0} means that the port number is
* automatically allocated, typically from an ephemeral port range.
* This port number can then be retrieved by calling
* {@link #getLocalPort getLocalPort}.
*
* <P>If there is a security manager, this method
* calls its {@code checkListen} method
* with the {@code port} argument
* as its argument to ensure the operation is allowed.
* This could result in a SecurityException.
*
* The {@code backlog} argument is the requested maximum number of
* pending connections on the socket. Its exact semantics are implementation
* specific. In particular, an implementation may impose a maximum length
* or may choose to ignore the parameter altogther. The value provided
* should be greater than {@code 0}. If it is less than or equal to
* {@code 0}, then an implementation specific default will be used.
* <P>
* @param port the port number, or {@code 0} to use a port
* number that is automatically allocated.
* @param backlog requested maximum length of the queue of incoming
* connections.
* @param bindAddr the local InetAddress the server will bind to
*
* @throws SecurityException if a security manager exists and
* its {@code checkListen} method doesn't allow the operation.
*
* @throws IOException if an I/O error occurs when opening the socket.
* @exception IllegalArgumentException if the port parameter is outside
* the specified range of valid port values, which is between
* 0 and 65535, inclusive.
*
* @see SocketOptions
* @see SocketImpl
* @see SecurityManager#checkListen
* @since JDK1.1
*/
public ServerSocket(int port, int backlog, InetAddress bindAddr) throws IOException {
setImpl();
if (port < 0 || port > 0xFFFF)
throw new IllegalArgumentException(
"Port value out of range: " + port);
if (backlog < 1)
backlog = 50;
try {
bind(new InetSocketAddress(bindAddr, port), backlog);
} catch(SecurityException e) {
close();
throw e;
} catch(IOException e) {
close();
throw e;
}
}
/**
* Get the {@code SocketImpl} attached to this socket, creating
* it if necessary.
*
* @return the {@code SocketImpl} attached to that ServerSocket.
* @throws SocketException if creation fails.
* @since 1.4
*/
SocketImpl getImpl() throws SocketException {
if (!created)
createImpl();
return impl;
}
private void checkOldImpl() {
if (impl == null)
return;
// SocketImpl.connect() is a protected method, therefore we need to use
// getDeclaredMethod, therefore we need permission to access the member
try {
AccessController.doPrivileged(
new PrivilegedExceptionAction<Void>() {
public Void run() throws NoSuchMethodException {
impl.getClass().getDeclaredMethod("connect",
SocketAddress.class,
int.class);
return null;
}
});
} catch (java.security.PrivilegedActionException e) {
oldImpl = true;
}
}
private void setImpl() {
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.setServerSocket(this);
}
/**
* Creates the socket implementation.
*
* @throws IOException if creation fails
* @since 1.4
*/
void createImpl() throws SocketException {
if (impl == null)
setImpl();
try {
impl.create(true);
created = true;
} catch (IOException e) {
throw new SocketException(e.getMessage());
}
}
/**
*
* Binds the {@code ServerSocket} to a specific address
* (IP address and port number).
* <p>
* If the address is {@code null}, then the system will pick up
* an ephemeral port and a valid local address to bind the socket.
* <p>
* @param endpoint The IP address and port number to bind to.
* @throws IOException if the bind operation fails, or if the socket
* is already bound.
* @throws SecurityException if a {@code SecurityManager} is present and
* its {@code checkListen} method doesn't allow the operation.
* @throws IllegalArgumentException if endpoint is a
* SocketAddress subclass not supported by this socket
* @since 1.4
*/
public void bind(SocketAddress endpoint) throws IOException {
bind(endpoint, 50);
}
/**
*
* Binds the {@code ServerSocket} to a specific address
* (IP address and port number).
* <p>
* If the address is {@code null}, then the system will pick up
* an ephemeral port and a valid local address to bind the socket.
* <P>
* The {@code backlog} argument is the requested maximum number of
* pending connections on the socket. Its exact semantics are implementation
* specific. In particular, an implementation may impose a maximum length
* or may choose to ignore the parameter altogther. The value provided
* should be greater than {@code 0}. If it is less than or equal to
* {@code 0}, then an implementation specific default will be used.
* @param endpoint The IP address and port number to bind to.
* @param backlog requested maximum length of the queue of
* incoming connections.
* @throws IOException if the bind operation fails, or if the socket
* is already bound.
* @throws SecurityException if a {@code SecurityManager} is present and
* its {@code checkListen} method doesn't allow the operation.
* @throws IllegalArgumentException if endpoint is a
* SocketAddress subclass not supported by this socket
* @since 1.4
*/
public void bind(SocketAddress endpoint, int backlog) throws IOException {
if (isClosed())
throw new SocketException("Socket is closed");
if (!oldImpl && isBound())
throw new SocketException("Already bound");
if (endpoint == null)
endpoint = new InetSocketAddress(0);
if (!(endpoint instanceof InetSocketAddress))
throw new IllegalArgumentException("Unsupported address type");
InetSocketAddress epoint = (InetSocketAddress) endpoint;
if (epoint.isUnresolved())
throw new SocketException("Unresolved address");
if (backlog < 1)
backlog = 50;
try {
SecurityManager security = System.getSecurityManager();
if (security != null)
security.checkListen(epoint.getPort());
getImpl().bind(epoint.getAddress(), epoint.getPort());
getImpl().listen(backlog);
bound = true;
} catch(SecurityException e) {
bound = false;
throw e;
} catch(IOException e) {
bound = false;
throw e;
}
}
/**
* Returns the local address of this server socket.
* <p>
* If the socket was bound prior to being {@link #close closed},
* then this method will continue to return the local address
* after the socket is closed.
* <p>
* If there is a security manager set, its {@code checkConnect} method is
* called with the local address and {@code -1} as its arguments to see
* if the operation is allowed. If the operation is not allowed,
* the {@link InetAddress#getLoopbackAddress loopback} address is returned.
*
* @return the address to which this socket is bound,
* or the loopback address if denied by the security manager,
* or {@code null} if the socket is unbound.
*
* @see SecurityManager#checkConnect
*/
public InetAddress getInetAddress() {
if (!isBound())
return null;
try {
InetAddress in = getImpl().getInetAddress();
SecurityManager sm = System.getSecurityManager();
if (sm != null)
sm.checkConnect(in.getHostAddress(), -1);
return in;
} catch (SecurityException e) {
return InetAddress.getLoopbackAddress();
} catch (SocketException e) {
// nothing
// If we're bound, the impl has been created
// so we shouldn't get here
}
return null;
}
/**
* Returns the port number on which this socket is listening.
* <p>
* If the socket was bound prior to being {@link #close closed},
* then this method will continue to return the port number
* after the socket is closed.
*
* @return the port number to which this socket is listening or
* -1 if the socket is not bound yet.
*/
public int getLocalPort() {
if (!isBound())
return -1;
try {
return getImpl().getLocalPort();
} catch (SocketException e) {
// nothing
// If we're bound, the impl has been created
// so we shouldn't get here
}
return -1;
}
/**
* Returns the address of the endpoint this socket is bound to.
* <p>
* If the socket was bound prior to being {@link #close closed},
* then this method will continue to return the address of the endpoint
* after the socket is closed.
* <p>
* If there is a security manager set, its {@code checkConnect} method is
* called with the local address and {@code -1} as its arguments to see
* if the operation is allowed. If the operation is not allowed,
* a {@code SocketAddress} representing the
* {@link InetAddress#getLoopbackAddress loopback} address and the local
* port to which the socket is bound is returned.
*
* @return a {@code SocketAddress} representing the local endpoint of
* this socket, or a {@code SocketAddress} representing the
* loopback address if denied by the security manager,
* or {@code null} if the socket is not bound yet.
*
* @see #getInetAddress()
* @see #getLocalPort()
* @see #bind(SocketAddress)
* @see SecurityManager#checkConnect
* @since 1.4
*/
public SocketAddress getLocalSocketAddress() {
if (!isBound())
return null;
return new InetSocketAddress(getInetAddress(), getLocalPort());
}
/**
* Listens for a connection to be made to this socket and accepts
* it. The method blocks until a connection is made.
*
* <p>A new Socket {@code s} is created and, if there
* is a security manager,
* the security manager's {@code checkAccept} method is called
* with {@code s.getInetAddress().getHostAddress()} and
* {@code s.getPort()}
* as its arguments to ensure the operation is allowed.
* This could result in a SecurityException.
*
* @exception IOException if an I/O error occurs when waiting for a
* connection.
* @exception SecurityException if a security manager exists and its
* {@code checkAccept} method doesn't allow the operation.
* @exception SocketTimeoutException if a timeout was previously set with setSoTimeout and
* the timeout has been reached.
* @exception java.nio.channels.IllegalBlockingModeException
* if this socket has an associated channel, the channel is in
* non-blocking mode, and there is no connection ready to be
* accepted
*
* @return the new Socket
* @see SecurityManager#checkAccept
* @revised 1.4
* @spec JSR-51
*/
public Socket accept() throws IOException {
if (isClosed())
throw new SocketException("Socket is closed");
if (!isBound())
throw new SocketException("Socket is not bound yet");
Socket s = new Socket((SocketImpl) null);
implAccept(s);
return s;
}
/**
* Subclasses of ServerSocket use this method to override accept()
* to return their own subclass of socket. So a FooServerSocket
* will typically hand this method an <i>empty FooSocket. On
* return from implAccept the FooSocket will be connected to a client.
*
* @param s the Socket
* @throws java.nio.channels.IllegalBlockingModeException
* if this socket has an associated channel,
* and the channel is in non-blocking mode
* @throws IOException if an I/O error occurs when waiting
* for a connection.
* @since JDK1.1
* @revised 1.4
* @spec JSR-51
*/
protected final void implAccept(Socket s) throws IOException {
SocketImpl si = null;
try {
if (s.impl == null)
s.setImpl();
else {
s.impl.reset();
}
si = s.impl;
s.impl = null;
si.address = new InetAddress();
si.fd = new FileDescriptor();
getImpl().accept(si);
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkAccept(si.getInetAddress().getHostAddress(),
si.getPort());
}
} catch (IOException e) {
if (si != null)
si.reset();
s.impl = si;
throw e;
} catch (SecurityException e) {
if (si != null)
si.reset();
s.impl = si;
throw e;
}
s.impl = si;
s.postAccept();
}
/**
* Closes this socket.
*
* Any thread currently blocked in {@link #accept()} will throw
* a {@link SocketException}.
*
* <p> If this socket has an associated channel then the channel is closed
* as well.
*
* @exception IOException if an I/O error occurs when closing the socket.
* @revised 1.4
* @spec JSR-51
*/
public void close() throws IOException {
synchronized(closeLock) {
if (isClosed())
return;
if (created)
impl.close();
closed = true;
}
}
/**
* Returns the unique {@link java.nio.channels.ServerSocketChannel} object
* associated with this socket, if any.
*
* <p> A server socket will have a channel if, and only if, the channel
* itself was created via the {@link
* java.nio.channels.ServerSocketChannel#open ServerSocketChannel.open}
* method.
*
* @return the server-socket channel associated with this socket,
* or {@code null} if this socket was not created
* for a channel
*
* @since 1.4
* @spec JSR-51
*/
public ServerSocketChannel getChannel() {
return null;
}
/**
* Returns the binding state of the ServerSocket.
*
* @return true if the ServerSocket successfully bound to an address
* @since 1.4
*/
public boolean isBound() {
// Before 1.3 ServerSockets were always bound during creation
return bound || oldImpl;
}
/**
* Returns the closed state of the ServerSocket.
*
* @return true if the socket has been closed
* @since 1.4
*/
public boolean isClosed() {
synchronized(closeLock) {
return closed;
}
}
/**
* Enable/disable {@link SocketOptions#SO_TIMEOUT SO_TIMEOUT} with the
* specified timeout, in milliseconds. With this option set to a non-zero
* timeout, a call to accept() for this ServerSocket
* will block for only this amount of time. If the timeout expires,
* a <B>java.net.SocketTimeoutException is raised, though the
* ServerSocket is still valid. The option <B>must be enabled
* prior to entering the blocking operation to have effect. The
* timeout must be {@code > 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 JDK1.1
* @see #getSoTimeout()
*/
public synchronized void setSoTimeout(int timeout) throws SocketException {
if (isClosed())
throw new SocketException("Socket is closed");
getImpl().setOption(SocketOptions.SO_TIMEOUT, new Integer(timeout));
}
/**
* Retrieve setting for {@link SocketOptions#SO_TIMEOUT SO_TIMEOUT}.
* 0 returns implies that the option is disabled (i.e., timeout of infinity).
* @return the {@link SocketOptions#SO_TIMEOUT SO_TIMEOUT} value
* @exception IOException if an I/O error occurs
* @since JDK1.1
* @see #setSoTimeout(int)
*/
public synchronized int getSoTimeout() throws IOException {
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;
}
}
/**
* Enable/disable the {@link SocketOptions#SO_REUSEADDR SO_REUSEADDR}
* socket option.
* <p>
* 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 {@code TIME_WAIT} state
* or {@code 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
* {@code SocketAddress} if there is a connection in the
* timeout state involving the socket address or port.
* <p>
* Enabling {@link SocketOptions#SO_REUSEADDR 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.
* <p>
* When a {@code ServerSocket} is created the initial setting
* of {@link SocketOptions#SO_REUSEADDR SO_REUSEADDR} is not defined.
* Applications can use {@link #getReuseAddress()} to determine the initial
* setting of {@link SocketOptions#SO_REUSEADDR SO_REUSEADDR}.
* <p>
* The behaviour when {@link SocketOptions#SO_REUSEADDR 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 {@link SocketOptions#SO_REUSEADDR SO_REUSEADDR}
* socket option, or the socket is closed.
* @since 1.4
* @see #getReuseAddress()
* @see #bind(SocketAddress)
* @see #isBound()
* @see #isClosed()
*/
public void setReuseAddress(boolean on) throws SocketException {
if (isClosed())
throw new SocketException("Socket is closed");
getImpl().setOption(SocketOptions.SO_REUSEADDR, Boolean.valueOf(on));
}
/**
* Tests if {@link SocketOptions#SO_REUSEADDR SO_REUSEADDR} is enabled.
*
* @return a {@code boolean} indicating whether or not
* {@link SocketOptions#SO_REUSEADDR 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)
*/
public boolean getReuseAddress() throws SocketException {
if (isClosed())
throw new SocketException("Socket is closed");
return ((Boolean) (getImpl().getOption(SocketOptions.SO_REUSEADDR))).booleanValue();
}
/**
* Returns the implementation address and implementation port of
* this socket as a {@code String}.
* <p>
* If there is a security manager set, its {@code checkConnect} method is
* called with the local address and {@code -1} as its arguments to see
* if the operation is allowed. If the operation is not allowed,
* an {@code InetAddress} representing the
* {@link InetAddress#getLoopbackAddress loopback} address is returned as
* the implementation address.
*
* @return a string representation of this socket.
*/
public String toString() {
if (!isBound())
return "ServerSocket[unbound]";
InetAddress in;
if (System.getSecurityManager() != null)
in = InetAddress.getLoopbackAddress();
else
in = impl.getInetAddress();
return "ServerSocket[addr=" + in +
",localport=" + impl.getLocalPort() + "]";
}
void setBound() {
bound = true;
}
void setCreated() {
created = true;
}
/**
* The factory for all server sockets.
*/
private static SocketImplFactory factory = null;
/**
* Sets the server socket implementation factory for the
* application. The factory can be specified only once.
* <p>
* When an application creates a new server socket, the socket
* implementation factory's {@code createSocketImpl} method is
* called to create the actual socket implementation.
* <p>
* Passing {@code null} to the method is a no-op unless the factory
* was already set.
* <p>
* If there is a security manager, this method first calls
* the security manager's {@code 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 has already been defined.
* @exception SecurityException if a security manager exists and its
* {@code checkSetFactory} method doesn't allow the operation.
* @see java.net.SocketImplFactory#createSocketImpl()
* @see SecurityManager#checkSetFactory
*/
public static synchronized void setSocketFactory(SocketImplFactory fac) throws IOException {
if (factory != null) {
throw new SocketException("factory already defined");
}
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkSetFactory();
}
factory = fac;
}
/**
* Sets a default proposed value for the
* {@link SocketOptions#SO_RCVBUF SO_RCVBUF} option for sockets
* accepted from this {@code ServerSocket}. The value actually set
* in the accepted socket must be determined by calling
* {@link Socket#getReceiveBufferSize()} after the socket
* is returned by {@link #accept()}.
* <p>
* The value of {@link SocketOptions#SO_RCVBUF SO_RCVBUF} is used both to
* set the size of the internal socket receive buffer, and to set the size
* of the TCP receive window that is advertized to the remote peer.
* <p>
* It is possible to change the value subsequently, by calling
* {@link Socket#setReceiveBufferSize(int)}. However, if the application
* wishes to allow a receive window larger than 64K bytes, as defined by RFC1323
* then the proposed value must be set in the ServerSocket <B>before
* it is bound to a local address. This implies, that the ServerSocket must be
* created with the no-argument constructor, then setReceiveBufferSize() must
* be called and lastly the ServerSocket is bound to an address by calling bind().
* <p>
* Failure to do this will not cause an error, and the buffer size may be set to the
* requested value but the TCP receive window in sockets accepted from
* this ServerSocket will be no larger than 64K bytes.
*
* @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 receive buffer
* size. This value must be greater than 0.
*
* @exception IllegalArgumentException if the
* value is 0 or is negative.
*
* @since 1.4
* @see #getReceiveBufferSize
*/
public synchronized void setReceiveBufferSize (int size) throws SocketException {
if (!(size > 0)) {
throw new IllegalArgumentException("negative receive size");
}
if (isClosed())
throw new SocketException("Socket is closed");
getImpl().setOption(SocketOptions.SO_RCVBUF, new Integer(size));
}
/**
* Gets the value of the {@link SocketOptions#SO_RCVBUF SO_RCVBUF} option
* for this {@code ServerSocket}, that is the proposed buffer size that
* will be used for Sockets accepted from this {@code ServerSocket}.
*
* <p>Note, the value actually set in the accepted socket is determined by
* calling {@link Socket#getReceiveBufferSize()}.
* @return the value of the {@link SocketOptions#SO_RCVBUF SO_RCVBUF}
* option for this {@code Socket}.
* @exception SocketException if there is an error
* in the underlying protocol, such as a TCP error.
* @see #setReceiveBufferSize(int)
* @since 1.4
*/
public synchronized int getReceiveBufferSize()
throws SocketException{
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;
}
/**
* Sets performance preferences for this ServerSocket.
*
* <p> 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.
*
* <p> 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. 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
* {@code (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 {@code (0, 1, 2)}.
*
* <p> Invoking this method after this socket has been bound
* will have no effect. This implies that in order to use this capability
* requires the socket to be created with the no-argument constructor.
*
* @param connectionTime
* An {@code int} expressing the relative importance of a short
* connection time
*
* @param latency
* An {@code int} expressing the relative importance of low
* latency
*
* @param bandwidth
* An {@code int} expressing the relative importance of high
* bandwidth
*
* @since 1.5
*/
public void setPerformancePreferences(int connectionTime,
int latency,
int bandwidth)
{
/* Not implemented yet */
}
}
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