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Chapter 15 The java.net Package |
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ServerSocket
Name
ServerSocketSynopsis
- Class Name:
-
java.net.ServerSocket
- Superclass:
-
java.lang.Object
- Immediate Subclasses:
-
None
- Interfaces Implemented:
-
None
- Availability:
-
JDK 1.0 or later
Description
The ServerSocket class represents a socket that listens for connection requests from clients on a specified port. When a connection is requested, a Socket object is created to handle the communication.
The low-level network access in ServerSocket is provided by a subclass of the abstract class SocketImpl. An application can change the server socket factory that creates the SocketImpl subclass by supplying a SocketImplFactory using the setSocketFactory() method. This feature allows an application to create sockets that are appropriate for the local network configuration and accommodate such things as firewalls.
Class Summary
public class java.net.ServerSocket extends java.lang.Object {
// Constructors
public ServerSocket(int port);
public ServerSocket(int port, int backlog);
public ServerSocket(int port, int backlog,
InetAddress bindAddr); // New in 1.1
// Class Methods
public static synchronized void setSocketFactory(SocketImplFactory fac);
// Instance Methods
public Socket accept();
public void close();
public InetAddress getInetAddress();
public int getLocalPort();
public synchronized int getSoTimeout() // New in 1.1
public synchronized void setSoTimeout(int timeout); // New in 1.1
public String toString();
// Protected Instance Methods
protected final void implAccept(Socket s); // New in 1.1
}
Constructors
ServerSocket
public ServerSocket(int port) throws IOException
- Parameters
-
- port
-
A port number, or 0 for any available port.
- port
- Throws
-
- IOException
-
If any kind of I/O error occurs.
- SecurityException
-
If the application is not allowed to listen on the given port.
- IOException
- Description
-
This method creates a server socket that listens for a connection on the given port. A default of 50 pending connections can be queued by the ServerSocket. Calling accept() removes a pending connections from the queue. If the queue is full, additional connection requests are refused.
If an application has specified a server socket factory, the createSocketImpl() method of that factory is called to create the actual socket implementation. Otherwise, the constructor creates a plain socket.
public ServerSocket(int port, int backlog) throws IOException
- Parameters
-
- port
-
A port number, or 0 for any available port.
- backlog
-
The maximum length of the pending connections queue.
- port
- Throws
-
- IOException
-
If any kind of I/O error occurs.
- SecurityException
-
If the application is not allowed to listen on the given port.
- IOException
- Description
-
This method creates a server socket that listens for a connection on the given port. The backlog parameter specifies how many pending connections can be queued by the ServerSocket. Calling accept() removes a pending connection from the queue. If the queue is full, additional connection requests are refused.
If an application has specified a server socket factory, the createSocketImpl() method of that factory is called to create the actual socket implementation. Otherwise, the constructor creates a plain socket.
public ServerSocket(int port, int backlog, InetAddress bindAddr) throws IOException
public ServerSocket(int port, int backlog, InetAddress bindAddr) throws IOException
- Availability
-
New as of JDK 1.1
- Parameters
-
- port
-
A port number, or 0 for any available port.
- backlog
-
The maximum length of the pending connections queue.
- bindAddr
-
A local address.
- port
- Throws
-
- IOException
-
If any kind of I/O error occurs.
- SecurityException
-
If the application is not allowed to listen on the given port.
- IOException
- Description
-
This method creates a server socket that listens for a connection on the given port of bindAddr. On machines with multiple addresses, bindAddr specifies the address on which this ServerSocket listens. The backlog parameter specifies how many pending connections can be queued by the ServerSocket. Calling accept() removes pending connections from the queue. If the queue is full, additional connection requests are refused.
If an application has specified a server socket factory, the createSocketImpl() method of that factory is called to create the actual socket implementation. Otherwise, the constructor creates a plain socket.
Class Methods
setSocketFactory
public static synchronized void setSocketFactory( SocketImplFactory fac) throws IOException
public static synchronized void setSocketFactory( SocketImplFactory fac) throws IOException
- Parameters
-
- fac
-
An object that implements SocketImplFactory.
- fac
- Throws
-
- IOException
-
If the factory has already been defined.
- SecurityException
-
If the application does not have permission to set the factory.
- IOException
- Description
-
This method is used to set the SocketImplFactory. This factory object produces instances of subclasses of SocketImpl that do the low-level work of server sockets. When a ServerSocket constructor is called, the createSocketImpl() method of the factory is called to create the server socket implementation.
Instance Methods
accept
public Socket accept() throws IOException
- Returns
-
A Socket object for the connection.
- Throws
-
- IOException
-
If any kind of I/O error occurs.
- SecurityException
-
If the application is not allowed to accept the connection.
- IOException
- Description
-
This method accepts a connection and returns a Socket object to handle communication. If there are pending connections, the method accepts a pending connection from the queue and returns immediately. Otherwise, the method may block until a connection is requested. If a time-out value has been specified using the setSoTimeout() method, accept() may time out and throw an InterruptedIOException if no connection is requested in the time-out period.
close
public void close() throws IOException
- Throws
-
- IOException
-
If any kind of I/O error occurs.
- IOException
- Description
-
This method closes this server socket, releasing any system resources it holds.
getInetAddress
public InetAddress getInetAddress()
- Returns
-
The IP address to which this ServerSocket is listening.
- Description
-
Generally, this method returns the address of the local host. However, a ServerSocket can be constructed with an alternate address using ServerSocket(int, int, InetAddress). The method returns null if the socket is not yet connected.
getLocalPort
public int getLocalPort()
- Returns
-
The port number to which this ServerSocket is listening.
- Description
-
This method returns the port number to which this object is connected.
getSoTimeout
public synchronized int getSoTimeout() throws IOException
- Availability
-
New as of JDK 1.1
- Returns
-
The receive timeout value for the socket.
- Throws
-
- IOException
-
If any kind of I/O error occurs.
- IOException
- Description
-
This method returns the receive time-out value for this socket. A value of zero indicates that accept() waits indefinitely for an incoming packet, while a non-zero value indicates the number of milliseconds it waits.
setSoTimeout
public synchronized void setSoTimeout(int timeout) throws SocketException
public synchronized void setSoTimeout(int timeout) throws SocketException
- Availability
-
New as of JDK 1.1
- Parameters
-
- timeout
-
The new time-out value, in milliseconds, for this socket.
- timeout
- Throws
-
- SocketException
-
If any kind of socket error occurs.
- SocketException
- Description
-
This method is used to set the time-out value that is used for accept(). A nonzero value is the length of time, in milliseconds, the ServerSocket should wait for a connection. A value of zero indicates that the ServerSocket should wait indefinitely. If a time-out value is needed, this method must be called before accept().
toString
public String toString()
- Returns
-
The string representation of this ServerSocket.
- Overrides
-
Object.toString()
- Description
-
This method returns a String that contains the address and port of this ServerSocket.
Protected Instance Methods
implAccept
protected final void implAccept(Socket s) throws IOException
- Availability
-
New as of JDK 1.1
- Parameters
-
- s
-
The Socket object to be connected.
- s
- Throws
-
- IOException
-
If any kind of I/O error occurs.
- SecurityException
-
If the application is not allowed to accept the connection.
- IOException
- Description
-
This method is a helper method for accept(). It can be overridden in subclasses of ServerSocket to support new subclasses of Socket.
Inherited Methods
|
Method |
Inherited From |
Method |
Inherited From |
|---|---|---|---|
|
clone() |
Object |
equals(Object) |
Object |
|
finalize() |
Object |
getClass() |
Object |
|
hashCode() |
Object |
notify() |
Object |
|
notifyAll() |
Object |
wait() |
Object |
|
wait(long) |
Object |
wait(long, int) |
Object |
See Also
InetAddress, IOException, SecurityException, Socket, SocketException, SocketImpl, SocketImplFactory
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| ProtocolException |  |
Socket |
