is new.
java.lang.Objectjava.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.
| 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
() 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. |
| 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
public ServerSocket(int port) throws
IOException
(Proxyproxy)
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 there is a security manager, its checkConnect method is called with the proxy host address and port number as its arguments. This could result in a SecurityException.
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.
Examples:
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.
- 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)
(int port)throws IOException
socket and binds it
local port number, with the specified backlog.
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.
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.
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.
specified port,
backlog - the maximum length of the queue.
public ServerSocket(int port, int backlog,
InetAddress
(int port, int backlog) throwsIOExceptionbindAddr) 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.
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 local TCP port
backlog - the listen backlog
bindAddr - the local InetAddress the server will bind to
SecurityException
- if a security manager exists and its checkListen method doesn't allow the operation.
Since:
JDK1.1
SocketOptions
SocketImpl
Method Detail
|
|---|
bind
publicvoid
bind
ServerSocket(
SocketAddress
(int port, int backlog,InetAddressendpoint)
bindAddr)throws IOException
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.
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.
endpoint - The IP address & port number to bind to.
IOException
- if the bind operation fails, or if the socket is already bound.
SecurityManager is present
IllegalArgumentException
- if endpoint is a SocketAddress subclass not supported by this socket
1.4
|
|---|
public void bind(SocketAddressendpoint, int backlog)
endpoint)throws IOException
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.
backlog - The listen backlog length.
getInetAddress
public
InetAddress
public voidgetInetAddress
bind()
(SocketAddressendpoint, int backlog) throwsIOException
Returns the local address of this server socket.
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.
Returns:
the address to which this socket is bound, or null if the socket is unbound.
getLocalPort
public int
publicInetAddressgetLocalPort
getInetAddress()
Returns the port on which this socket is listening.
port number
listening
-1
not bound yet.
getLocalSocketAddress
public
SocketAddress
public intgetLocalSocketAddress
getLocalPort()
Returns the address of the endpoint this socket is bound to, or null if it is not bound yet.
a SocketAddress representing the local endpoint of this socket, or null if it is not bound yet.
Since:
1.4
See Also:
getInetAddress()
,
getLocalPort()
,
bind(SocketAddress)
accept
publicSocket
SocketAddressaccept
getLocalSocketAddress() 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.
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.
SocketTimeoutException
- if a timeout was previously set with setSoTimeout and the timeout has been reached.
IllegalBlockingModeException
- if this socket has an associated channel, and the channel is in non-blocking mode.
SecurityManager.checkAccept(java.lang.String, int)
implAccept
protected final void
publicSocketimplAccept
accept(
Socket
() throwsIOExceptions) 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.
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.
Parameters:
s -
the
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.
Since:
JDK1.1
close
public void
protected final voidclose
implAccept() throws
IOException
(Sockets) throwsIOException
Closes this socket. Any thread currently blocked in
accept()
will throw a
SocketException
.
If this socket has an associated channel then the channel is closed as well.
- if an I/O error occurs when closing the socket.
getChannel
public
ServerSocketChannel
public voidgetChannel
close()
() throwsIOException
Returns the unique
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.
If this socket has an associated channel then the channel is closed as well.
Returns:
the server-socket channel associated with this socket, or
null
if this socket was not created for a channel
Since:
1.4
isBound
public boolean
publicServerSocketChannelisBound
getChannel()
Returns the binding state of the ServerSocket.
A server socket will have a channel if, and only if, the channel itself was created via the
ServerSocketChannel.open
method.
true if the ServerSocket succesfuly bound to an address
isClosed
public booleanisClosed
isBound()
closed
true if the socket has been closed
setSoTimeout
publicvoid
booleansetSoTimeout
isClosed(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.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.
Parameters:
timeout - the specified timeout, in milliseconds
Throws:
SocketException
- if there is an error in the underlying protocol, such as a TCP error.
JDK1.1
See Also:
getSoTimeout()
getSoTimeout
publicint
voidgetSoTimeout
setSoTimeout() throws
IOException
(int timeout) throwsSocketException
Retrive setting for SO_TIMEOUT. 0 returns implies that the option is disabled (i.e., timeout of infinity).
Returns:
the SO_TIMEOUT value
IOException
- if an I/O error occurs
setSoTimeout(int)
setReuseAddress
publicvoid
intsetReuseAddress
getSoTimeout(boolean on) throws
SocketException
() throwsIOException
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
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.
Parameters:
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.
1.4
getReuseAddress()
,
bind(SocketAddress)
,
isBound()
,
isClosed()
getReuseAddress
publicboolean
voidgetReuseAddress
setReuseAddress()
(boolean on)throws SocketException
Tests if SO_REUSEADDR is enabled.
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.
Returns:
a boolean indicating whether or not SO_REUSEADDR is enabled.
- if there is an error in the underlying protocol, such as a TCP error.
setReuseAddress(boolean)
toString
public
String
public booleantoString
getReuseAddress()
() throwsSocketException
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
publicStringsetSocketFactory
toString(
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.
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.
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()
setReceiveBufferSize
publicstaticvoidsetReceiveBufferSize
setSocketFactory(int size) throws
SocketException
(SocketImplFactoryfac) throwsIOException
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
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().
When an application creates a new server socket, the socket implementation factory's createSocketImpl method is called to create the actual socket implementation.
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.
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.
size - the size to which to set the receive buffer size. This value must be greater than 0.
- if there is an error in the underlying protocol, such as a TCP error.
IllegalArgumentException
- if the value is 0 or is negative.
Since:
1.4
getReceiveBufferSize()
getReceiveBufferSize
publicint
voidgetReceiveBufferSize
setReceiveBufferSize()
(int size)throws SocketException
Gets the
of
, 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
Socket.getReceiveBufferSize()
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.
Returns:
the value of the SO_RCVBUF option for this
Socket
.
setReceiveBufferSize(int)
setPerformancePreferences
publicvoid
intsetPerformancePreferences
getReceiveBufferSize(int connectionTime, int latency, int bandwidth)
() throwsSocketException
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
Gets the value of the SO_RCVBUF option for this
(1, 0, 0)
ServerSocket
. 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
, that is the proposed buffer size that will be used for Sockets accepted from this
(0, 1, 2)
ServerSocket
.
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.
Note, the value actually set in the accepted socket is determined by calling
Socket.getReceiveBufferSize()
.
Parameters:
connectionTime - An
int
expressing the relative importance of a short connection time
latency - An
int
expressing the relative importance of low latency
bandwidth - An
int
expressing the relative importance of high bandwidth
1.5