* The actual work of the server socket is performed by an instance
* of the 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;
/**
* 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 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}.
*
* The maximum queue length for incoming connection indications (a
* request to connect) is set to 50. If a connection
* indication arrives when the queue is full, the connection is refused.
*
* 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 checkListen method is called
* with the port argument
* as its argument to ensure the operation is allowed.
* This could result in a SecurityException.
*
*
* @param port the port number, or 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 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 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}.
*
* The maximum queue length for incoming connection indications (a
* request to connect) is set to the backlog parameter. If
* a connection indication arrives when the queue is full, the
* connection is refused.
*
* 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 checkListen method is called
* with the port argument
* as its argument to ensure the operation is allowed.
* This could result in a SecurityException.
*
*
The backlog argument must be a positive
* value greater than 0. If the value passed is equal or less
* than 0, then the default value will be assumed.
*
*
* @param port the port number, or 0 to use a port
* number that is automatically allocated.
* @param backlog the maximum length of the queue.
*
* @exception IOException if an I/O error occurs when opening the socket.
* @exception SecurityException
* if a security manager exists and its 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 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 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 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}.
*
*
If there is a security manager, this method
* calls its checkListen method
* with the port argument
* as its argument to ensure the operation is allowed.
* This could result in a SecurityException.
*
*
The backlog argument must be a positive
* value greater than 0. If the value passed is equal or less
* than 0, then the default value will be assumed.
*
* @param port the port number, or 0 to use a port
* number that is automatically allocated.
* @param backlog the listen backlog
* @param bindAddr the local InetAddress the server will bind to
*
* @throws SecurityException if a security manager exists and
* its 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 SocketImpl attached to this socket, creating
* it if necessary.
*
* @return the 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() {
public Object run() throws NoSuchMethodException {
Class[] cl = new Class[2];
cl[0] = SocketAddress.class;
cl[1] = Integer.TYPE;
impl.getClass().getDeclaredMethod("connect", cl);
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 ServerSocket to a specific address
* (IP address and port number).
*
* If the address is null, then the system will pick up
* an ephemeral port and a valid local address to bind the socket.
*
* @param endpoint The IP address & port number to bind to.
* @throws IOException if the bind operation fails, or if the socket
* is already bound.
* @throws SecurityException if a SecurityManager is present and
* its 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 ServerSocket to a specific address
* (IP address and port number).
*
* If the address is null, then the system will pick up
* an ephemeral port and a valid local address to bind the socket.
*
* The backlog argument must be a positive
* value greater than 0. If the value passed is equal or less
* than 0, then the default value will be assumed.
* @param endpoint The IP address & port number to bind to.
* @param backlog The listen backlog length.
* @throws IOException if the bind operation fails, or if the socket
* is already bound.
* @throws SecurityException if a SecurityManager is present and
* its 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.
*
* 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.
*
* @return the address to which this socket is bound,
* or null if the socket is unbound.
*/
public InetAddress getInetAddress() {
if (!isBound())
return null;
try {
return getImpl().getInetAddress();
} 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.
*
* 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, or
* null if it is not bound yet.
*
* 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.
*
* @return a SocketAddress representing the local endpoint of this
* socket, or null if it is not bound yet.
* @see #getInetAddress()
* @see #getLocalPort()
* @see #bind(SocketAddress)
* @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.
*
*
A new Socket s is created and, if there
* is a security manager,
* the security manager's checkAccept method is called
* with s.getInetAddress().getHostAddress() and
* 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
* 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 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}.
*
*
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. * *
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 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 succesfuly 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 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 java.net.SocketTimeoutException is raised, though the * ServerSocket 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 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 SO_TIMEOUT. 0 returns implies that the * option is disabled (i.e., timeout of infinity). * @return the 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 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 ServerSocket is created the initial setting * of SO_REUSEADDR is not defined. Applications can * use {@link #getReuseAddress()} to determine the initial * setting of SO_REUSEADDR. *
* 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 #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 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)
*/
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 String.
*
* @return a string representation of this socket.
*/
public String toString() {
if (!isBound())
return "ServerSocket[unbound]";
return "ServerSocket[addr=" + impl.getInetAddress() +
",port=" + impl.getPort() +
",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.
*
* When an application creates a new server 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 has already been 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
*/
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 SO_RCVBUF option for sockets
* accepted from this 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()}.
*
* The value of 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. *
* 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 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(). *
* 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 SO_RCVBUF option for this ServerSocket, * that is the proposed buffer size that will be used for Sockets accepted * from this ServerSocket. * *
Note, the value actually set in the accepted socket is determined by * calling {@link Socket#getReceiveBufferSize()}. * @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 1.4 */ 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. * *
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. 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 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 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 */ public void setPerformancePreferences(int connectionTime, int latency, int bandwidth) { /* Not implemented yet */ } }