java.net
Class ServerSocket

java.lang.Object
  |
  +--java.net.ServerSocket

public class ServerSocket

extends Object

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.

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.

Since:

JDK1.0

See Also:

SocketImpl, setSocketFactory(java.net.SocketImplFactory)

Constructor Summary

ServerSocket(int port)
Creates a server socket on a specified port.

ServerSocket(int port, int backlog)
Creates a server socket and binds it to the specified local port number, with the specified backlog.

ServerSocket(int port, int backlog, InetAddress bindAddr)
Create a server with the specified port, listen backlog, and local IP address to bind to.

Method Summary

Socket	accept() Listens for a connection to be made to this socket and accepts it.
void	close() Closes this socket.
InetAddress	getInetAddress() Returns the local address of this server socket.
int	getLocalPort() Returns the port on which this socket is listening.
int	getSoTimeout() Retrive setting for SO_TIMEOUT.
protected void	implAccept(Socket s) Subclasses of ServerSocket use this method to override accept() to return their own subclass of socket.
static void	setSocketFactory(SocketImplFactory fac) Sets the server socket implementation factory for the application.
void	setSoTimeout(int timeout) Enable/disable SO_TIMEOUT with the specified timeout, in milliseconds.
String	toString() Returns the implementation address and implementation port of this socket as a String.

Methods inherited from class java.lang.Object

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

Constructor Detail

ServerSocket

public ServerSocket(int port)
             throws IOException

Creates a server socket on a 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.

Parameters:

port - the port number, or 0 to use any free port.

Throws:

IOException - if an I/O error occurs when opening the socket.

SecurityException - if a security manager exists and its checkListen method doesn't allow the operation.

See Also:

SocketImpl, SocketImplFactory.createSocketImpl(), setSocketFactory(java.net.SocketImplFactory), SecurityManager.checkListen(int)

ServerSocket

public ServerSocket(int port,
                    int backlog)
             throws IOException

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.

Parameters:

port - the specified port, or 0 to use any free port.

backlog - the maximum length of the queue.

Throws:

IOException - if an I/O error occurs when opening the socket.

SecurityException - if a security manager exists and its checkListen method doesn't allow the operation.

See Also:

SocketImpl, SocketImplFactory.createSocketImpl(), setSocketFactory(java.net.SocketImplFactory), SecurityManager.checkListen(int)

ServerSocket

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

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.

Parameters:

port - the local TCP port

backlog - the listen backlog

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.

IOException - if an I/O error occurs when opening the socket.

Since:

JDK1.1

See Also:

SocketOptions, SocketImpl, SecurityManager.checkListen(int)

Method Detail

getInetAddress

public InetAddress getInetAddress()

Returns the local address of this server socket.

Returns:

the address to which this socket is connected, or null if the socket is not yet connected.

getLocalPort

public int getLocalPort()

Returns the port on which this socket is listening.

Returns:

the port number to which this socket is listening.

accept

public Socket accept()
              throws IOException

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.

Returns:

the new Socket

Throws:

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

SecurityException - if a security manager exists and its checkListen method doesn't allow the operation.

See Also:

SecurityManager.checkAccept(java.lang.String, int)

implAccept

protected final void implAccept(Socket s)
                         throws IOException

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.

Parameters:

s - the Socket

Throws:

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

Since:

JDK1.1

close

public void close()
           throws IOException

Closes this socket.

Throws:

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

setSoTimeout

public void setSoTimeout(int timeout)
                  throws SocketException

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.io.InterruptedIOException 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.

Parameters:

timeout - the specified timeout, in milliseconds

Throws:

SocketException - if there is an error in the underlying protocol, such as a TCP error.

Since:

JDK1.1

See Also:

getSoTimeout()

getSoTimeout

public int getSoTimeout()
                 throws IOException

Retrive setting for SO_TIMEOUT. 0 returns implies that the option is disabled (i.e., timeout of infinity).

Returns:

the SO_TIMEOUT value

Throws:

IOException - if an I/O error occurs

Since:

JDK1.1

See Also:

setSoTimeout(int)

toString

public String toString()

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

Overrides:

toString in class Object

Returns:

a string representation of this socket.

setSocketFactory

public static void setSocketFactory(SocketImplFactory fac)
                             throws IOException

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.

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.

Parameters:

fac - the desired factory.

Throws:

IOException - if an I/O error occurs when setting the socket factory.

SocketException - if the factory has already been defined.

SecurityException - if a security manager exists and its checkSetFactory method doesn't allow the operation.

See Also:

SocketImplFactory.createSocketImpl(), SecurityManager.checkSetFactory()