org.sapia.ubik.net.mplex

Class MultiplexServerSocket

java.lang.Object

java.net.ServerSocket

org.sapia.ubik.net.mplex.MultiplexServerSocket

All Implemented Interfaces:

Closeable, AutoCloseable, Runnable

public class MultiplexServerSocket
extends ServerSocket
implements Runnable

This class is the main server socket that multiplexes the traditionnal ServerSocket. That means that it listens on the port of the server socket and it provides a mechanism to register different handlers for these new incoming socket connections. These handlers are called socket connectors and they can be used to process multiple types of data streams over the same socket.

For instance, using this MultiplexServerSocket you could handle serialized Java objects and HTTP requests using two different connectors (two distinct handling logic), same host/port. This is achieved through a read-ahead on the incoming stream of data from a new client socket connection. When a new incoming connection is requested by a client, all the registered StreamSelectors are used to determine which socket connector will handle the new connection.

The internals of this MultiplexServerSocket are simple: an instance of this class works on an asynchronous process were new socket connections are first accepted, and then selected. These two steps are described as follows:

1. acceptor: This first step involves the low-level logic of virtual machine that resides under the Java I/O package. When a client connects to the server, a new MultiplexSocket is created on the server-side; the acceptor adds that new connection/socket to the internal pending queue.
2. selector: The selector listens on the queue of accepted connections and performs the logic of going through all the candidate socket connectors to determine which one of them handles the new socket connection; if none of the registered connectors is.

To perform this process, the MultiplexServerSocket contains two distinct pools of threads that are configurable using the setAcceptorDaemonThread(int) and setSelectorDaemonThread(int) methods.

The primary goal of this class is to keep the "standard" (non-NIO) programming model of the JDK regarding socket handling. Whether you use this server socket directly or you use a socket connector, the logic is still the same for the client that receives new incoming connections: it calls an accept() method that blocks until a new connection is made. For integration with actual running systems, an adapter is available to make a socket connector look like a server socket. We used that strategy with the open-source Simple HTTP server and it worked transparently and fluidly.

Author:

Jean-Cedric Desrochers

See Also:

MultiplexSocket, MultiplexSocketConnector, ServerSocketAdapter, StreamSelector

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	MultiplexServerSocket.SelectorTask This class is responsible of the selection logic of the multiplex.

Field Summary

Fields

Modifier and Type	Field and Description
static short	DEFAULT_ACCEPTOR_DAEMON_THREAD The default number of acceptor daemon thread used to accept connections.
static short	DEFAULT_READ_AHEAD_BUFFER_SIZE The default number of bytes read ahead fom incoming socket connections.
static short	DEFAULT_SELECTOR_DAEMON_THREAD The default number of selector daemon thread used to accept connections.

Constructor Summary

Constructors

Constructor and Description
MultiplexServerSocket() Creates a new MultiplexServerSocket instance.
MultiplexServerSocket(int port) Creates a new MultiplexServerSocket instance.
MultiplexServerSocket(int port, int backlog) Creates a new MultiplexServerSocket instance.
MultiplexServerSocket(int port, int backlog, InetAddress bindAddr) Creates a new MultiplexServerSocket instance.

Method Summary

Methods

Modifier and Type	Method and Description
Socket	accept() Listens for a connection to be made to this socket and accepts it.
void	close() Closes this multiplex server socket.
MultiplexSocketConnector	createSocketConnector(StreamSelector aSelector) This factory method creates a socket connector through which a client will be able to receive incoming socket connections.
int	getAcceptorDaemonThread() Returns the number of daemon threads used to accept incoming connections.
int	getReadAheadBufferSize() Returns the size of the buffer used to pre-read the incoming bytes of the accepted connection.
int	getSelectorDaemonThread() Returns the number of daemon threads used to select an connector for incoming connections.
void	removeSocketConnector(MultiplexSocketConnector aConnector) Removes the socket connector passed in from the list of available connectors associated with this server socket.
void	run() Implements the Runnable interface and it performs the asynchronous acceptor logic of the multiplex.
void	setAcceptorDaemonThread(int maxThread) Changes the number of daemon threads used to accept incoming connections.
void	setReadAheadBufferSize(int aSize) Changes the size of the read ahead buffer size.
void	setSelectorDaemonThread(int maxThread) Changes the number of daemon threads used to select connectors for incoming connections.
void	setSoTimeout(int timeout)
String	toString() Returns the implementation address and implementation port of this socket as a String.

Methods inherited from class java.net.ServerSocket

bind, bind, getChannel, getInetAddress, getLocalPort, getLocalSocketAddress, getReceiveBufferSize, getReuseAddress, getSoTimeout, implAccept, isBound, isClosed, setPerformancePreferences, setReceiveBufferSize, setReuseAddress, setSocketFactory

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

DEFAULT_READ_AHEAD_BUFFER_SIZE

public static final short DEFAULT_READ_AHEAD_BUFFER_SIZE

The default number of bytes read ahead fom incoming socket connections.

See Also:

Constant Field Values

DEFAULT_ACCEPTOR_DAEMON_THREAD

public static final short DEFAULT_ACCEPTOR_DAEMON_THREAD

The default number of acceptor daemon thread used to accept connections.

See Also:

Constant Field Values

DEFAULT_SELECTOR_DAEMON_THREAD

public static final short DEFAULT_SELECTOR_DAEMON_THREAD

The default number of selector daemon thread used to accept connections.

See Also:

Constant Field Values

Constructor Detail

MultiplexServerSocket

public MultiplexServerSocket()
                      throws IOException

Creates a new MultiplexServerSocket instance. The server socket is unbound

Throws:

IOException - If an error occurs opening the socket.

MultiplexServerSocket

public MultiplexServerSocket(int port)
                      throws IOException

Creates a new MultiplexServerSocket instance. The new server will be bound on the speficied port, or to a free port if the value passed in is 0 (zero). 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.

Parameters:

port - The port number to bind the server or 0 to use any port.

Throws:

IOException - If an error occurs when opening the socket.

MultiplexServerSocket

public MultiplexServerSocket(int port,
                     int backlog)
                      throws IOException

Creates a new MultiplexServerSocket instance. The new server will be bound on the speficied port, or to a free port if the value passed in is 0 (zero). 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.

Parameters:

port - The port number to bind the server or 0 oi use any port.

backlog - The maximum length of the queue.

Throws:

IOException - If an error occurs when opening the socket.

MultiplexServerSocket

public MultiplexServerSocket(int port,
                     int backlog,
                     InetAddress bindAddr)
                      throws IOException

Creates a new MultiplexServerSocket instance. The new server will be bound on the speficied port, or to a free port if the value passed in is 0 (zero). The server will use the local IP address represented by the bindAddr passed in. 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.

Parameters:

port - The port number to bind the server or 0 oi use any port.

backlog - The maximum length of the queue.

bindAddr - The local TCP address the server will bind to. If null the server will accept connections on any/all local addresses.

Throws:

IOException - If an error occurs when opening the socket.

Method Detail

setSoTimeout

public void setSoTimeout(int timeout)
                  throws SocketException

Overrides:

setSoTimeout in class ServerSocket

Throws:

SocketException

getReadAheadBufferSize

public int getReadAheadBufferSize()

Returns the size of the buffer used to pre-read the incoming bytes of the accepted connection.

Returns:

The size of the read ahead buffer size.

setReadAheadBufferSize

public void setReadAheadBufferSize(int aSize)

Changes the size of the read ahead buffer size. This method can only be called before starting the server (ie. the initial call to the method accept().

Parameters:

aSize - The new size.

Throws:

IllegalStateException - If the server is already running.

getAcceptorDaemonThread

public int getAcceptorDaemonThread()

Returns the number of daemon threads used to accept incoming connections.

Returns:

The number of daemon threads used to accept incoming connections.

getSelectorDaemonThread

public int getSelectorDaemonThread()

Returns the number of daemon threads used to select an connector for incoming connections.

Returns:

The number of daemon threads used to select an connector for incoming connections.

setAcceptorDaemonThread

public void setAcceptorDaemonThread(int maxThread)

Changes the number of daemon threads used to accept incoming connections.

Parameters:

maxThread - The new numbe of running daemon.

Throws:

IllegalStateException - If the server is already running.

setSelectorDaemonThread

public void setSelectorDaemonThread(int maxThread)

Changes the number of daemon threads used to select connectors for incoming connections.

Parameters:

maxThread - The new numbe of running daemon.

Throws:

IllegalStateException - If the server is already running.

createSocketConnector

public MultiplexSocketConnector createSocketConnector(StreamSelector aSelector)

This factory method creates a socket connector through which a client will be able to receive incoming socket connections. The stream selector passed in will be used by this multiplex server socket to determine if an incoming socket connection must be handled by the created socket connector.

Parameters:

aSelector - The stream selector to assign to the created socket connector.

Returns:

The created socket connector.

Throws:

IllegalStateException - If this server socket is closed.

removeSocketConnector

public void removeSocketConnector(MultiplexSocketConnector aConnector)

Removes the socket connector passed in from the list of available connectors associated with this server socket. After this method the multiplex server socket will no longer send new incoming socket connection to the socket connector.

Parameters:

aConnector - The socket connector to remove from this server socket.

accept

public Socket accept()
              throws IOException

Listens for a connection to be made to this socket and accepts it. The default connector of this server socket will be used to act as the main port of entry for clients directly using the server socket instead of the default socket connector. The method blocks until a connection is made.

Overrides:

accept in class ServerSocket

Returns:

The new Socket

Throws:

IOException - If an I/O error occurs when waiting for a connection.

SocketTimeoutException - if a timeout was previously set with setSoTimeout and the timeout has been reached.

close

public void close()
           throws IOException

Closes this multiplex server socket. If socket connectors are associated to this server scket then they are closed as well.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Overrides:

close in class ServerSocket

Throws:

IOException - If an I/O error occurs when closing the socket.

toString

public String toString()

Returns the implementation address and implementation port of this socket as a String.

Overrides:

toString in class ServerSocket

Returns:

A string representation of this socket.

run

public void run()

Implements the Runnable interface and it performs the asynchronous acceptor logic of the multiplex. Used by the acceptor threads, it listens on the underlying server socket and dispacthes all the incoming socket connections to the queue of accepted socket connection. The client socket connections put in that queue are then processed asynchronously by the selector threads.

Specified by:

run in interface Runnable