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)SocketImpljava.nio.channels.SocketChannel
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.java.lang.IllegalArgumentException if the proxy is of an invalid type
or null.java.lang.SecurityException if a security manager is present and
permission to connect to the proxy is
denied.ProxySelectorProxy
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.
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.java.io.IOException if an I/O error occurs when creating the socket.java.lang.SecurityException if a security manager exists and its
checkConnect method doesn't allow the operation.setSocketImplFactory(java.net.SocketImplFactory)SocketImplSocketImplFactory.createSocketImpl()java.lang.SecurityManager.checkConnect(java.lang.String,int)
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.java.io.IOException if an I/O error occurs when creating the socket.java.lang.SecurityException if a security manager exists and its
checkConnect method doesn't allow the operation.setSocketImplFactory(java.net.SocketImplFactory)SocketImplSocketImplFactory.createSocketImpl()java.lang.SecurityManager.checkConnect(java.lang.String,int)
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 tojava.io.IOException if an I/O error occurs when creating the socket.java.lang.SecurityException if a security manager exists and its
checkConnect method doesn't allow the operation.java.lang.SecurityManager.checkConnect(java.lang.String,int)
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 tojava.io.IOException if an I/O error occurs when creating the socket.java.lang.SecurityException if a security manager exists and its
checkConnect method doesn't allow the operation.java.lang.SecurityManager.checkConnect(java.lang.String,int)
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.java.io.IOException if an I/O error occurs when creating the socket.java.lang.SecurityException if a security manager exists and its
checkConnect method doesn't allow the operation.setSocketImplFactory(java.net.SocketImplFactory)SocketImplSocketImplFactory.createSocketImpl()java.lang.SecurityManager.checkConnect(java.lang.String,int)
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.java.io.IOException if an I/O error occurs when creating the socket.java.lang.SecurityException if a security manager exists and its
checkConnect method doesn't allow the operation.setSocketImplFactory(java.net.SocketImplFactory)SocketImplSocketImplFactory.createSocketImpl()java.lang.SecurityManager.checkConnect(java.lang.String,int)stream a boolean value : true for a TCP socket,
false for UDP.java.io.IOException if creation failsSocketImpl attached to this socket, creating
it if necessary.
SocketImpl attached to that ServerSocket.SocketException if creation failsendpoint the SocketAddressjava.io.IOException if an error occurs during the connectionjava.nio.channels.IllegalBlockingModeException
if this socket has an associated channel,
and the channel is in non-blocking modejava.lang.IllegalArgumentException if endpoint is null or is a
SocketAddress subclass not supported by this socketendpoint the SocketAddresstimeout the timeout value to be used in milliseconds.java.io.IOException if an error occurs during the connectionSocketTimeoutException if timeout expires before connectingjava.nio.channels.IllegalBlockingModeException
if this socket has an associated channel,
and the channel is in non-blocking modejava.lang.IllegalArgumentException if endpoint is null or is a
SocketAddress subclass not supported by this socket
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 tojava.io.IOException if the bind operation fails, or if the socket
is already bound.java.lang.IllegalArgumentException if bindpoint is a
SocketAddress subclass not supported by this socketisBound()null if it is unconnected.
SocketAddress reprensenting the remote endpoint of this
socket, or null if it is not connected yet.getInetAddress()getPort()connect(java.net.SocketAddress,int)connect(java.net.SocketAddress)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(java.net.SocketAddress)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 java.nio.channels.ServerSocketChannel.accept()
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 java.nio.channels.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.
java.io.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() 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 java.nio.channels.IllegalBlockingModeException
Closing the returned OutputStream
will close the associated socket.
java.io.IOException if an I/O error occurs when creating the
output stream or if the socket is not connected.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()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)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.java.lang.IllegalArgumentException if the linger value is negative.getSoLinger()SocketException if there is an error
in the underlying protocol, such as a TCP error.setSoLinger(boolean,int)data The byte of data to sendjava.io.IOException if there is an error
sending the data.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()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)timeout the specified timeout, in milliseconds.SocketException if there is an error
in the underlying protocol, such as a TCP error.getSoTimeout()SocketException if there is an error
in the underlying protocol, such as a TCP error.setSoTimeout(int)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.java.lang.IllegalArgumentException if the
value is 0 or is negative.getSendBufferSize()SocketException if there is an error
in the underlying protocol, such as a TCP error.setSendBufferSize(int)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)size the size to which to set the receive buffer
size. This value must be greater than 0.java.lang.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)SocketException if there is an error
in the underlying protocol, such as a TCP error.setReceiveBufferSize(int)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()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) 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()
As the underlying network implementation may ignore the
traffic class or type-of-service set using setTrafficClass(int)setTrafficClass(int)
SocketException if there is an error obtaining the
traffic class or type-of-service value.setTrafficClass(int)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(java.net.SocketAddress)
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()
on whether to enable or disable the socket optionSocketException if an error occurs enabling or
disabling the SO_RESUEADDR socket option,
or the socket is closed.getReuseAddress()bind(java.net.SocketAddress)isClosed()isBound()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)
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.
java.io.IOException if an I/O error occurs when closing this socket.isClosed()If you read from a socket input stream after invoking shutdownInput() on the socket, the stream will return EOF.
java.io.IOException if an I/O error occurs when shutting down this
socket.shutdownOutput()close()setSoLinger(boolean,int)isInputShutdown()java.io.IOException if an I/O error occurs when shutting down this
socket.shutdownInput()close()setSoLinger(boolean,int)isOutputShutdown()bind(java.net.SocketAddress)close()shutdownInput()shutdownOutput()
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.java.io.IOException if an I/O error occurs when setting the
socket factory.SocketException if the factory is already defined.java.lang.SecurityException if a security manager exists and its
checkSetFactory method doesn't allow the operation.SocketImplFactory.createSocketImpl()java.lang.SecurityManager.checkSetFactory()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