File	Doc	Category	Size	Date	Package
ServerSocket.java	API Doc	Java SE 5 API	28921	Fri Aug 26 14:57:08 BST 2005	java.net

ServerSocket

• java.lang.Object

Fields Summary
private boolean	created Various states of this socket.
private boolean	bound
private boolean	closed
private Object	closeLock
private SocketImpl	impl The implementation of this Socket.
private boolean	oldImpl Are we using an older SocketImpl?
private static SocketImplFactory	factory The factory for all server sockets.

Constructors Summary
public ServerSocket() Creates an unbound server socket. exception IOException IO error when opening the socket. revised 1.4 setImpl();
public ServerSocket(int port) Creates a server socket, bound to the specified port. A port of 0 creates a socket on any free port. 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 any free port. 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. see java.net.SocketImpl see java.net.SocketImplFactory#createSocketImpl() see java.net.ServerSocket#setSocketFactory(java.net.SocketImplFactory) see SecurityManager#checkListen this(port, 50, null);
public ServerSocket(int port, int backlog) Creates a server socket and binds it to the specified local port number, with the specified backlog. A port number of 0 creates a socket on any free port. 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 if equal or less than 0, then the default value will be assumed. param port the specified port, or 0 to use any free port. 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. see java.net.SocketImpl see java.net.SocketImplFactory#createSocketImpl() see java.net.ServerSocket#setSocketFactory(java.net.SocketImplFactory) see SecurityManager#checkListen this(port, backlog, null);
public ServerSocket(int port, int backlog, InetAddress bindAddr) 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. 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 if equal or less than 0, then the default value will be assumed. param port the local TCP port 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. see SocketOptions see SocketImpl see SecurityManager#checkListen since JDK1.1 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; }

Methods Summary
public java.net.Socket	accept() 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 checkListen 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 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;
public void	bind(java.net.SocketAddress endpoint, int backlog) 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 if 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 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; }
public void	bind(java.net.SocketAddress endpoint) 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 bind(endpoint, 50);
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; }
public void	close() 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 synchronized(closeLock) { if (isClosed()) return; if (created) impl.close(); closed = true; }
void	createImpl() Creates the socket implementation. throws IOException if creation fails since 1.4 if (impl == null) setImpl(); try { impl.create(true); created = true; } catch (IOException e) { throw new SocketException(e.getMessage()); }
public java.nio.channels.ServerSocketChannel	getChannel() 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 return null;
java.net.SocketImpl	getImpl() 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(); return impl;
public java.net.InetAddress	getInetAddress() Returns the local address of this server socket. return the address to which this socket is bound, or null if the socket is unbound. if (!isBound()) return null; try { return getImpl().getInetAddress(); } catch (SocketException e) { // nothing // If we're bound, the the impl has been created // so we shouldn't get here } return null;
public int	getLocalPort() Returns the port on which this socket is listening. return the port number to which this socket is listening or -1 if the socket is not bound yet. if (!isBound()) return -1; try { return getImpl().getLocalPort(); } catch (SocketException e) { // nothing // If we're bound, the the impl has been created // so we shouldn't get here } return -1;
public java.net.SocketAddress	getLocalSocketAddress() 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 #getInetAddress() see #getLocalPort() see #bind(SocketAddress) since 1.4 if (!isBound()) return null; return new InetSocketAddress(getInetAddress(), getLocalPort());
public synchronized int	getReceiveBufferSize() 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 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 boolean	getReuseAddress() 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 int	getSoTimeout() Retrive 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) 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; }
protected final void	implAccept(java.net.Socket 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 SocketImpl si = null; try { if (s.impl == null) s.setImpl(); 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();
public boolean	isBound() Returns the binding state of the ServerSocket. return true if the ServerSocket succesfuly bound to an address since 1.4 // Before 1.3 ServerSockets were always bound during creation return bound || oldImpl;
public boolean	isClosed() Returns the closed state of the ServerSocket. return true if the socket has been closed since 1.4 synchronized(closeLock) { return closed; }
void	setBound() bound = true;
void	setCreated() created = 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);
public void	setPerformancePreferences(int connectionTime, int latency, int bandwidth) 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 /* Not implemented yet */
public synchronized void	setReceiveBufferSize(int size) 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 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));
public void	setReuseAddress(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 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() if (isClosed()) throw new SocketException("Socket is closed"); getImpl().setOption(SocketOptions.SO_REUSEADDR, Boolean.valueOf(on));
public synchronized void	setSoTimeout(int timeout) 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() if (isClosed()) throw new SocketException("Socket is closed"); getImpl().setOption(SocketOptions.SO_TIMEOUT, new Integer(timeout));
public static synchronized void	setSocketFactory(java.net.SocketImplFactory fac) 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 if (factory != null) { throw new SocketException("factory already defined"); } SecurityManager security = System.getSecurityManager(); if (security != null) { security.checkSetFactory(); } factory = fac;
public java.lang.String	toString() Returns the implementation address and implementation port of this socket as a String. return a string representation of this socket. if (!isBound()) return "ServerSocket[unbound]"; return "ServerSocket[addr=" + impl.getInetAddress() + ",port=" + impl.getPort() + ",localport=" + impl.getLocalPort() + "]";