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Java™ Platform Standard Ed. 6 |
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java.lang.Object java.net.Socket
public class Socket
This class implements client sockets (also called just "sockets"). A socket is an endpoint for communication between two machines.
The actual work of the socket is performed by an instance of the
SocketImpl
class. An application, by changing
the socket factory that creates the socket implementation,
can configure itself to create sockets appropriate to the local
firewall.
setSocketImplFactory(java.net.SocketImplFactory)
,
SocketImpl
,
SocketChannel
Constructor Summary | |
---|---|
|
Socket()
Creates an unconnected socket, with the system-default type of SocketImpl. |
|
Socket(InetAddress address,
int port)
Creates a stream socket and connects it to the specified port number at the specified IP address. |
|
Socket(InetAddress host,
int port,
boolean stream)
Deprecated. Use DatagramSocket instead for UDP transport. |
|
Socket(InetAddress address,
int port,
InetAddress localAddr,
int localPort)
Creates a socket and connects it to the specified remote address on the specified remote port. |
|
Socket(Proxy proxy)
Creates an unconnected socket, specifying the type of proxy, if any, that should be used regardless of any other settings. |
protected |
Socket(SocketImpl impl)
Creates an unconnected Socket with a user-specified SocketImpl. |
|
Socket(String host,
int port)
Creates a stream socket and connects it to the specified port number on the named host. |
|
Socket(String host,
int port,
boolean stream)
Deprecated. Use DatagramSocket instead for UDP transport. |
|
Socket(String host,
int port,
InetAddress localAddr,
int localPort)
Creates a socket and connects it to the specified remote host on the specified remote port. |
Method Summary | |
---|---|
void |
bind(SocketAddress bindpoint)
Binds the socket to a local address. |
void |
close()
Closes this socket. |
void |
connect(SocketAddress endpoint)
Connects this socket to the server. |
void |
connect(SocketAddress endpoint,
int timeout)
Connects this socket to the server with a specified timeout value. |
SocketChannel |
getChannel()
Returns the unique SocketChannel
object associated with this socket, if any. |
InetAddress |
getInetAddress()
Returns the address to which the socket is connected. |
InputStream |
getInputStream()
Returns an input stream for this socket. |
boolean |
getKeepAlive()
Tests if SO_KEEPALIVE is enabled. |
InetAddress |
getLocalAddress()
Gets the local address to which the socket is bound. |
int |
getLocalPort()
Returns the local port to which this socket is bound. |
SocketAddress |
getLocalSocketAddress()
Returns the address of the endpoint this socket is bound to, or null if it is not bound yet. |
boolean |
getOOBInline()
Tests if OOBINLINE is enabled. |
OutputStream |
getOutputStream()
Returns an output stream for this socket. |
int |
getPort()
Returns the remote port to which this socket is connected. |
int |
getReceiveBufferSize()
Gets the value of the SO_RCVBUF option for this Socket, that is the buffer size used by the platform for input on this Socket. |
SocketAddress |
getRemoteSocketAddress()
Returns the address of the endpoint this socket is connected to, or null if it is unconnected. |
boolean |
getReuseAddress()
Tests if SO_REUSEADDR is enabled. |
int |
getSendBufferSize()
Get value of the SO_SNDBUF option for this Socket, that is the buffer size used by the platform for output on this Socket. |
int |
getSoLinger()
Returns setting for SO_LINGER. |
int |
getSoTimeout()
Returns setting for SO_TIMEOUT. |
boolean |
getTcpNoDelay()
Tests if TCP_NODELAY is enabled. |
int |
getTrafficClass()
Gets traffic class or type-of-service in the IP header for packets sent from this Socket |
boolean |
isBound()
Returns the binding state of the socket. |
boolean |
isClosed()
Returns the closed state of the socket. |
boolean |
isConnected()
Returns the connection state of the socket. |
boolean |
isInputShutdown()
Returns whether the read-half of the socket connection is closed. |
boolean |
isOutputShutdown()
Returns whether the write-half of the socket connection is closed. |
void |
sendUrgentData(int data)
Send one byte of urgent data on the socket. |
void |
setKeepAlive(boolean on)
Enable/disable SO_KEEPALIVE. |
void |
setOOBInline(boolean on)
Enable/disable OOBINLINE (receipt of TCP urgent data) By default, this option is disabled and TCP urgent data received on a socket is silently discarded. |
void |
setPerformancePreferences(int connectionTime,
int latency,
int bandwidth)
Sets performance preferences for this socket. |
void |
setReceiveBufferSize(int size)
Sets the SO_RCVBUF option to the specified value for this Socket. |
void |
setReuseAddress(boolean on)
Enable/disable the SO_REUSEADDR socket option. |
void |
setSendBufferSize(int size)
Sets the SO_SNDBUF option to the specified value for this Socket. |
static void |
setSocketImplFactory(SocketImplFactory fac)
Sets the client socket implementation factory for the application. |
void |
setSoLinger(boolean on,
int linger)
Enable/disable SO_LINGER with the specified linger time in seconds. |
void |
setSoTimeout(int timeout)
Enable/disable SO_TIMEOUT with the specified timeout, in milliseconds. |
void |
setTcpNoDelay(boolean on)
Enable/disable TCP_NODELAY (disable/enable Nagle's algorithm). |
void |
setTrafficClass(int tc)
Sets traffic class or type-of-service octet in the IP header for packets sent from this Socket. |
void |
shutdownInput()
Places the input stream for this socket at "end of stream". |
void |
shutdownOutput()
Disables the output stream for this socket. |
String |
toString()
Converts this socket to a String . |
Methods inherited from class java.lang.Object |
---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Constructor Detail |
---|
public Socket()
public Socket(Proxy proxy)
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.
Examples:
Socket s = new Socket(Proxy.NO_PROXY);
will create
a plain socket ignoring any other proxy configuration.Socket s = new Socket(new Proxy(Proxy.Type.SOCKS, new InetSocketAddress("socks.mydom.com", 1080)));
will create a socket connecting through the specified SOCKS proxy
server.
proxy
- a Proxy
object specifying what kind
of proxying should be used.
IllegalArgumentException
- if the proxy is of an invalid type
or null
.
SecurityException
- if a security manager is present and
permission to connect to the proxy is
denied.ProxySelector
,
Proxy
protected Socket(SocketImpl impl) throws SocketException
impl
- an instance of a SocketImpl
the subclass wishes to use on the Socket.
SocketException
- if there is an error in the underlying protocol,
such as a TCP error.public Socket(String host, int port) throws UnknownHostException, IOException
If the specified host is null it is the equivalent of
specifying the address as InetAddress.getByName
(null).
In other words, it is equivalent to specifying an address of the
loopback interface.
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
checkConnect
method is called
with the host address and port
as its arguments. This could result in a SecurityException.
host
- the host name, or null
for the loopback address.port
- the port number.
UnknownHostException
- if the IP address of
the host could not be determined.
IOException
- if an I/O error occurs when creating the socket.
SecurityException
- if a security manager exists and its
checkConnect
method doesn't allow the operation.setSocketImplFactory(java.net.SocketImplFactory)
,
SocketImpl
,
SocketImplFactory.createSocketImpl()
,
SecurityManager.checkConnect(java.lang.String, int)
public Socket(InetAddress address, int port) throws IOException
If the application has specified a 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
checkConnect
method is called
with the host address and port
as its arguments. This could result in a SecurityException.
address
- the IP address.port
- the port number.
IOException
- if an I/O error occurs when creating the socket.
SecurityException
- if a security manager exists and its
checkConnect
method doesn't allow the operation.setSocketImplFactory(java.net.SocketImplFactory)
,
SocketImpl
,
SocketImplFactory.createSocketImpl()
,
SecurityManager.checkConnect(java.lang.String, int)
public Socket(String host, int port, InetAddress localAddr, int localPort) throws IOException
If the specified host is null it is the equivalent of
specifying the address as InetAddress.getByName
(null).
In other words, it is equivalent to specifying an address of the
loopback interface.
If there is a security manager, its
checkConnect
method is called
with the host address and port
as its arguments. This could result in a SecurityException.
host
- the name of the remote host, or null
for the loopback address.port
- the remote portlocalAddr
- the local address the socket is bound tolocalPort
- the local port the socket is bound to
IOException
- if an I/O error occurs when creating the socket.
SecurityException
- if a security manager exists and its
checkConnect
method doesn't allow the operation.SecurityManager.checkConnect(java.lang.String, int)
public Socket(InetAddress address, int port, InetAddress localAddr, int localPort) throws IOException
If there is a security manager, its
checkConnect
method is called
with the host address and port
as its arguments. This could result in a SecurityException.
address
- the remote addressport
- the remote portlocalAddr
- the local address the socket is bound tolocalPort
- the local port the socket is bound to
IOException
- if an I/O error occurs when creating the socket.
SecurityException
- if a security manager exists and its
checkConnect
method doesn't allow the operation.SecurityManager.checkConnect(java.lang.String, int)
@Deprecated public Socket(String host, int port, boolean stream) throws IOException
If the specified host is null it is the equivalent of
specifying the address as InetAddress.getByName
(null).
In other words, it is equivalent to specifying an address of the
loopback interface.
If the stream argument is true
, this creates a
stream socket. If the stream argument is false
, it
creates a datagram socket.
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
checkConnect
method is called
with the host address and port
as its arguments. This could result in a SecurityException.
If a UDP socket is used, TCP/IP related socket options will not apply.
host
- the host name, or null
for the loopback address.port
- the port number.stream
- a boolean
indicating whether this is
a stream socket or a datagram socket.
IOException
- if an I/O error occurs when creating the socket.
SecurityException
- if a security manager exists and its
checkConnect
method doesn't allow the operation.setSocketImplFactory(java.net.SocketImplFactory)
,
SocketImpl
,
SocketImplFactory.createSocketImpl()
,
SecurityManager.checkConnect(java.lang.String, int)
@Deprecated public Socket(InetAddress host, int port, boolean stream) throws IOException
If the stream argument is true
, this creates a
stream socket. If the stream argument is false
, it
creates a datagram socket.
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
checkConnect
method is called
with host.getHostAddress()
and port
as its arguments. This could result in a SecurityException.
If UDP socket is used, TCP/IP related socket options will not apply.
host
- the IP address.port
- the port number.stream
- if true
, create a stream socket;
otherwise, create a datagram socket.
IOException
- if an I/O error occurs when creating the socket.
SecurityException
- if a security manager exists and its
checkConnect
method doesn't allow the operation.setSocketImplFactory(java.net.SocketImplFactory)
,
SocketImpl
,
SocketImplFactory.createSocketImpl()
,
SecurityManager.checkConnect(java.lang.String, int)
Method Detail |
---|
public void connect(SocketAddress endpoint) throws IOException
endpoint
- the SocketAddress
IOException
- if an error occurs during the connection
IllegalBlockingModeException
- if this socket has an associated channel,
and the channel is in non-blocking mode
IllegalArgumentException
- if endpoint is null or is a
SocketAddress subclass not supported by this socketpublic void connect(SocketAddress endpoint, int timeout) throws IOException
endpoint
- the SocketAddress
timeout
- the timeout value to be used in milliseconds.
IOException
- if an error occurs during the connection
SocketTimeoutException
- if timeout expires before connecting
IllegalBlockingModeException
- if this socket has an associated channel,
and the channel is in non-blocking mode
IllegalArgumentException
- if endpoint is null or is a
SocketAddress subclass not supported by this socketpublic void bind(SocketAddress bindpoint) 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.
bindpoint
- the SocketAddress
to bind to
IOException
- if the bind operation fails, or if the socket
is already bound.
IllegalArgumentException
- if bindpoint is a
SocketAddress subclass not supported by this socketisBound()
public InetAddress getInetAddress()
null
if the socket is not connected.public InetAddress getLocalAddress()
InetAddress.anyLocalAddress()
if the socket is not bound yet.public int getPort()
public int getLocalPort()
public SocketAddress getRemoteSocketAddress()
null
if it is unconnected.
SocketAddress
reprensenting the remote endpoint of this
socket, or null
if it is not connected yet.getInetAddress()
,
getPort()
,
connect(SocketAddress, int)
,
connect(SocketAddress)
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.getLocalAddress()
,
getLocalPort()
,
bind(SocketAddress)
public SocketChannel getChannel()
SocketChannel
object associated with this socket, if any.
A socket will have a channel if, and only if, the channel itself was
created via the SocketChannel.open
or ServerSocketChannel.accept
methods.
public InputStream getInputStream() throws IOException
If this socket has an associated channel then the resulting input
stream delegates all of its operations to the channel. If the channel
is in non-blocking mode then the input stream's read operations
will throw an IllegalBlockingModeException
.
Under abnormal conditions the underlying connection may be broken by the remote host or the network software (for example a connection reset in the case of TCP connections). When a broken connection is detected by the network software the following applies to the returned input stream :-
The network software may discard bytes that are buffered
by the socket. Bytes that aren't discarded by the network
software can be read using read
.
If there are no bytes buffered on the socket, or all
buffered bytes have been consumed by
read
, then all subsequent
calls to read
will throw an
IOException
.
If there are no bytes buffered on the socket, and the
socket has not been closed using close
, then
available
will
return 0
.
Closing the returned InputStream
will close the associated socket.
IOException
- if an I/O error occurs when creating the
input stream, the socket is closed, the socket is
not connected, or the socket input has been shutdown
using shutdownInput()
public OutputStream getOutputStream() throws IOException
If this socket has an associated channel then the resulting output
stream delegates all of its operations to the channel. If the channel
is in non-blocking mode then the output stream's write
operations will throw an IllegalBlockingModeException
.
Closing the returned OutputStream
will close the associated socket.
IOException
- if an I/O error occurs when creating the
output stream or if the socket is not connected.public void setTcpNoDelay(boolean on) throws SocketException
on
- true
to enable TCP_NODELAY,
false
to disable.
SocketException
- if there is an error
in the underlying protocol, such as a TCP error.getTcpNoDelay()
public boolean getTcpNoDelay() throws SocketException
boolean
indicating whether or not TCP_NODELAY is enabled.
SocketException
- if there is an error
in the underlying protocol, such as a TCP error.setTcpNoDelay(boolean)
public void setSoLinger(boolean on, int linger) throws SocketException
on
- whether or not to linger on.linger
- how long to linger for, if on is true.
SocketException
- if there is an error
in the underlying protocol, such as a TCP error.
IllegalArgumentException
- if the linger value is negative.getSoLinger()
public int getSoLinger() throws SocketException
SocketException
- if there is an error
in the underlying protocol, such as a TCP error.setSoLinger(boolean, int)
public void sendUrgentData(int data) throws IOException
data
- The byte of data to send
IOException
- if there is an error
sending the data.public void setOOBInline(boolean on) throws SocketException
Note, only limited support is provided for handling incoming urgent data. In particular, no notification of incoming urgent data is provided and there is no capability to distinguish between normal data and urgent data unless provided by a higher level protocol.
on
- true
to enable OOBINLINE,
false
to disable.
SocketException
- if there is an error
in the underlying protocol, such as a TCP error.getOOBInline()
public boolean getOOBInline() throws SocketException
boolean
indicating whether or not OOBINLINE is enabled.
SocketException
- if there is an error
in the underlying protocol, such as a TCP error.setOOBInline(boolean)
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 SocketException
SocketException
- if there is an error
in the underlying protocol, such as a TCP error.setSoTimeout(int)
public void setSendBufferSize(int size) throws SocketException
Because SO_SNDBUF is a hint, applications that want to
verify what size the buffers were set to should call
getSendBufferSize()
.
size
- the size to which to set the send 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.getSendBufferSize()
public int getSendBufferSize() throws SocketException
SocketException
- if there is an error
in the underlying protocol, such as a TCP error.setSendBufferSize(int)
public void setReceiveBufferSize(int size) throws SocketException
Increasing the receive buffer size can increase the performance of network I/O for high-volume connection, while decreasing it can help reduce the backlog of incoming data.
Because SO_RCVBUF is a hint, applications that want to
verify what size the buffers were set to should call
getReceiveBufferSize()
.
The value of SO_RCVBUF is also used to set the TCP receive window that is advertized to the remote peer. Generally, the window size can be modified at any time when a socket is connected. However, if a receive window larger than 64K is required then this must be requested before the socket is connected to the remote peer. There are two cases to be aware of:
ServerSocket.setReceiveBufferSize(int)
before the ServerSocket
is bound to a local address.
size
- the size to which to set the receive buffer
size. This value must be greater than 0.
IllegalArgumentException
- if the value is 0 or is
negative.
SocketException
- if there is an error
in the underlying protocol, such as a TCP error.getReceiveBufferSize()
,
ServerSocket.setReceiveBufferSize(int)
public int getReceiveBufferSize() throws SocketException
SocketException
- if there is an error
in the underlying protocol, such as a TCP error.setReceiveBufferSize(int)
public void setKeepAlive(boolean on) throws SocketException
on
- whether or not to have socket keep alive turned on.
SocketException
- if there is an error
in the underlying protocol, such as a TCP error.getKeepAlive()
public boolean getKeepAlive() throws SocketException
boolean
indicating whether or not SO_KEEPALIVE is enabled.
SocketException
- if there is an error
in the underlying protocol, such as a TCP error.setKeepAlive(boolean)
public void setTrafficClass(int tc) throws SocketException
The tc must be in the range 0 <= tc <=
255
or an IllegalArgumentException will be thrown.
Notes:
For Internet Protocol v4 the value consists of an octet with precedence and TOS fields as detailed in RFC 1349. The TOS field is bitset created by bitwise-or'ing values such the following :-
IPTOS_LOWCOST (0x02)
IPTOS_RELIABILITY (0x04)
IPTOS_THROUGHPUT (0x08)
IPTOS_LOWDELAY (0x10)
Setting bits in the precedence field may result in a SocketException indicating that the operation is not permitted.
As RFC 1122 section 4.2.4.2 indicates, a compliant TCP implementation should, but is not required to, let application change the TOS field during the lifetime of a connection. So whether the type-of-service field can be changed after the TCP connection has been established depends on the implementation in the underlying platform. Applications should not assume that they can change the TOS field after the connection.
For Internet Protocol v6 tc
is the value that
would be placed into the sin6_flowinfo field of the IP header.
tc
- an int
value for the bitset.
SocketException
- if there is an error setting the
traffic class or type-of-servicegetTrafficClass()
public int getTrafficClass() throws SocketException
As the underlying network implementation may ignore the
traffic class or type-of-service set using setTrafficClass(int)
this method may return a different value than was previously
set using the setTrafficClass(int)
method on this Socket.
SocketException
- if there is an error obtaining the
traffic class or type-of-service value.setTrafficClass(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 Socket is created the initial setting of SO_REUSEADDR is disabled.
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)
,
isClosed()
,
isBound()
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 void close() throws IOException
Any thread currently blocked in an I/O operation upon this socket
will throw a SocketException
.
Once a socket has been closed, it is not available for further networking use (i.e. can't be reconnected or rebound). A new socket needs to be created.
Closing this socket will also close the socket's
InputStream
and
OutputStream
.
If this socket has an associated channel then the channel is closed as well.
IOException
- if an I/O error occurs when closing this socket.isClosed()
public void shutdownInput() throws IOException
If you read from a socket input stream after invoking shutdownInput() on the socket, the stream will return EOF.
IOException
- if an I/O error occurs when shutting down this
socket.shutdownOutput()
,
close()
,
setSoLinger(boolean, int)
,
isInputShutdown()
public void shutdownOutput() throws IOException
IOException
- if an I/O error occurs when shutting down this
socket.shutdownInput()
,
close()
,
setSoLinger(boolean, int)
,
isOutputShutdown()
public String toString()
String
.
toString
in class Object
public boolean isConnected()
public boolean isBound()
bind(java.net.SocketAddress)
public boolean isClosed()
close()
public boolean isInputShutdown()
shutdownInput()
public boolean isOutputShutdown()
shutdownOutput()
public static void setSocketImplFactory(SocketImplFactory fac) throws IOException
When an application creates a new client 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 is already defined.
SecurityException
- if a security manager exists and its
checkSetFactory
method doesn't allow the operation.SocketImplFactory.createSocketImpl()
,
SecurityManager.checkSetFactory()
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. Negative values represent a lower priority than positive values. 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 connected will have no effect.
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
|
Java™ Platform Standard Ed. 6 |
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