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Java™ Platform Standard Ed. 6 |
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java.lang.Object java.net.ServerSocket
public class ServerSocket
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.
SocketImpl
,
setSocketFactory(java.net.SocketImplFactory)
,
ServerSocketChannel
Constructor Summary | |
---|---|
ServerSocket()
Creates an unbound server socket. |
|
ServerSocket(int port)
Creates a server socket, bound to the 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 |
bind(SocketAddress endpoint)
Binds the ServerSocket to a specific address
(IP address and port number). |
void |
bind(SocketAddress endpoint,
int backlog)
Binds the ServerSocket to a specific address
(IP address and port number). |
void |
close()
Closes this socket. |
ServerSocketChannel |
getChannel()
Returns the unique ServerSocketChannel object
associated with this socket, if any. |
InetAddress |
getInetAddress()
Returns the local address of this server socket. |
int |
getLocalPort()
Returns the port on which this socket is listening. |
SocketAddress |
getLocalSocketAddress()
Returns the address of the endpoint this socket is bound to, or null if it is not bound yet. |
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. |
boolean |
getReuseAddress()
Tests if SO_REUSEADDR is enabled. |
int |
getSoTimeout()
Retrieve 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. |
boolean |
isBound()
Returns the binding state of the ServerSocket. |
boolean |
isClosed()
Returns the closed state of the ServerSocket. |
void |
setPerformancePreferences(int connectionTime,
int latency,
int bandwidth)
Sets performance preferences for this ServerSocket. |
void |
setReceiveBufferSize(int size)
Sets a default proposed value for the SO_RCVBUF option for sockets accepted from this ServerSocket. |
void |
setReuseAddress(boolean on)
Enable/disable the SO_REUSEADDR socket option. |
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 |
---|
public ServerSocket() throws IOException
IOException
- IO error when opening the socket.public ServerSocket(int port) throws IOException
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.
port
- the port number, or 0
to use any
free port.
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.SocketImpl
,
SocketImplFactory.createSocketImpl()
,
setSocketFactory(java.net.SocketImplFactory)
,
SecurityManager.checkListen(int)
public ServerSocket(int port, int backlog) throws IOException
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.
port
- the specified port, or 0
to use
any free port.backlog
- the maximum length of the queue.
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.SocketImpl
,
SocketImplFactory.createSocketImpl()
,
setSocketFactory(java.net.SocketImplFactory)
,
SecurityManager.checkListen(int)
public ServerSocket(int port, int backlog, InetAddress bindAddr) throws IOException
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.
port
- the local TCP portbacklog
- the listen backlogbindAddr
- the local InetAddress the server will bind to
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.SocketOptions
,
SocketImpl
,
SecurityManager.checkListen(int)
Method Detail |
---|
public void bind(SocketAddress endpoint) throws IOException
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.
endpoint
- The IP address & port number to bind to.
IOException
- if the bind operation fails, or if the socket
is already bound.
SecurityException
- if a SecurityManager
is present and
its checkListen
method doesn't allow the operation.
IllegalArgumentException
- if endpoint is a
SocketAddress subclass not supported by this socketpublic void bind(SocketAddress endpoint, int backlog) throws IOException
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.
endpoint
- The IP address & port number to bind to.backlog
- The listen backlog length.
IOException
- if the bind operation fails, or if the socket
is already bound.
SecurityException
- if a SecurityManager
is present and
its checkListen
method doesn't allow the operation.
IllegalArgumentException
- if endpoint is a
SocketAddress subclass not supported by this socketpublic InetAddress getInetAddress()
null
if the socket is unbound.public int getLocalPort()
public SocketAddress getLocalSocketAddress()
null
if it is not bound yet.
SocketAddress
representing the local endpoint of this
socket, or null
if it is not bound yet.getInetAddress()
,
getLocalPort()
,
bind(SocketAddress)
public Socket accept() throws IOException
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.
IOException
- if an I/O error occurs when waiting for a
connection.
SecurityException
- if a security manager exists and its
checkAccept
method doesn't allow the operation.
SocketTimeoutException
- if a timeout was previously set with setSoTimeout and
the timeout has been reached.
IllegalBlockingModeException
- if this socket has an associated channel, the channel is in
non-blocking mode, and there is no connection ready to be
acceptedSecurityManager.checkAccept(java.lang.String, int)
protected final void implAccept(Socket s) throws IOException
s
- the Socket
IllegalBlockingModeException
- if this socket has an associated channel,
and the channel is in non-blocking mode
IOException
- if an I/O error occurs when waiting
for a connection.public void close() throws IOException
accept()
will throw
a SocketException
.
If this socket has an associated channel then the channel is closed as well.
IOException
- if an I/O error occurs when closing the socket.public ServerSocketChannel getChannel()
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 ServerSocketChannel.open
method.
public boolean isBound()
public boolean isClosed()
public void setSoTimeout(int timeout) throws SocketException
timeout
- the specified timeout, in milliseconds
SocketException
- if there is an error in
the underlying protocol, such as a TCP error.getSoTimeout()
public int getSoTimeout() throws IOException
IOException
- if an I/O error occurssetSoTimeout(int)
public void setReuseAddress(boolean on) throws SocketException
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 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 getReuseAddress()
to determine the initial
setting of SO_REUSEADDR.
The behaviour when SO_REUSEADDR is enabled or
disabled after a socket is bound (See isBound()
)
is not defined.
on
- whether to enable or disable the socket option
SocketException
- if an error occurs enabling or
disabling the SO_RESUEADDR socket option,
or the socket is closed.getReuseAddress()
,
bind(SocketAddress)
,
isBound()
,
isClosed()
public boolean getReuseAddress() throws SocketException
boolean
indicating whether or not SO_REUSEADDR is enabled.
SocketException
- if there is an error
in the underlying protocol, such as a TCP error.setReuseAddress(boolean)
public String toString()
String
.
toString
in class Object
public static void setSocketFactory(SocketImplFactory fac) throws IOException
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.
fac
- the desired factory.
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.SocketImplFactory.createSocketImpl()
,
SecurityManager.checkSetFactory()
public void setReceiveBufferSize(int size) throws SocketException
Socket.getReceiveBufferSize()
after the socket
is returned by 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
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.
size
- the size to which to set the receive buffer
size. This value must be greater than 0.
SocketException
- if there is an error
in the underlying protocol, such as a TCP error.
IllegalArgumentException
- if the
value is 0 or is negative.getReceiveBufferSize()
public int getReceiveBufferSize() throws SocketException
Note, the value actually set in the accepted socket is determined by
calling Socket.getReceiveBufferSize()
.
SocketException
- if there is an error
in the underlying protocol, such as a TCP error.setReceiveBufferSize(int)
public void setPerformancePreferences(int connectionTime, int latency, int bandwidth)
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.
connectionTime
- An int expressing the relative importance of a short
connection timelatency
- An int expressing the relative importance of low
latencybandwidth
- An int expressing the relative importance of high
bandwidth
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Java™ Platform Standard Ed. 6 |
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