Class Socket
- All Implemented Interfaces:
Closeable
,AutoCloseable
- Direct Known Subclasses:
SSLSocket
The actual work of the socket is performed by an instance of the
SocketImpl
class.
The Socket
class defines convenience
methods to set and get several socket options. This class also
defines the setOption
and getOption
methods to set
and query socket options.
A Socket
support the following options:
Additional (implementation specific) options may also be supported.
Option Name Description SO_SNDBUF
The size of the socket send buffer SO_RCVBUF
The size of the socket receive buffer SO_KEEPALIVE
Keep connection alive SO_REUSEADDR
Re-use address SO_LINGER
Linger on close if data is present (when configured in blocking mode only) TCP_NODELAY
Disable the Nagle algorithm
- Since:
- 1.0
- See Also:
-
Constructor Summary
ModifierConstructorDescriptionSocket()
Creates an unconnected Socket.Creates a stream socket and connects it to the specified port number on the named host.Deprecated, for removal: This API element is subject to removal in a future version.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.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, for removal: This API element is subject to removal in a future version.UseDatagramSocket
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.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. -
Method Summary
Modifier and TypeMethodDescriptionvoid
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.Returns the uniqueSocketChannel
object associated with this socket, if any.Returns the address to which the socket is connected.Returns an input stream for this socket.boolean
Tests ifSO_KEEPALIVE
is enabled.Gets the local address to which the socket is bound.int
Returns the local port number to which this socket is bound.Returns the address of the endpoint this socket is bound to.boolean
Tests ifSO_OOBINLINE
is enabled.<T> T
getOption
(SocketOption<T> name) Returns the value of a socket option.Returns an output stream for this socket.int
getPort()
Returns the remote port number to which this socket is connected.int
Gets the value of theSO_RCVBUF
option for thisSocket
, that is the buffer size used by the platform for input on thisSocket
.Returns the address of the endpoint this socket is connected to, ornull
if it is unconnected.boolean
Tests ifSO_REUSEADDR
is enabled.int
Get value of theSO_SNDBUF
option for thisSocket
, that is the buffer size used by the platform for output on thisSocket
.int
Returns setting forSO_LINGER
.int
Returns setting forSO_TIMEOUT
. 0 returns implies that the option is disabled (i.e., timeout of infinity).boolean
Tests ifTCP_NODELAY
is enabled.int
Gets traffic class or type-of-service in the IP header for packets sent from this Socketboolean
isBound()
Returns the binding state of the socket.boolean
isClosed()
Returns the closed state of the socket.boolean
Returns the connection state of the socket.boolean
Returns whether the read-half of the socket connection is closed.boolean
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/disableSO_KEEPALIVE
.void
setOOBInline
(boolean on) Enable/disableSO_OOBINLINE
(receipt of TCP urgent data) By default, this option is disabled and TCP urgent data received on a socket is silently discarded.<T> Socket
setOption
(SocketOption<T> name, T value) Sets the value of a socket option.void
setPerformancePreferences
(int connectionTime, int latency, int bandwidth) Sets performance preferences for this socket.void
setReceiveBufferSize
(int size) Sets theSO_RCVBUF
option to the specified value for thisSocket
.void
setReuseAddress
(boolean on) Enable/disable theSO_REUSEADDR
socket option.void
setSendBufferSize
(int size) Sets theSO_SNDBUF
option to the specified value for thisSocket
.static void
Deprecated.Use aSocketFactory
and subclassSocket
directly.void
setSoLinger
(boolean on, int linger) Enable/disableSO_LINGER
with the specified linger time in seconds.void
setSoTimeout
(int timeout) Enable/disableSO_TIMEOUT
with the specified timeout, in milliseconds.void
setTcpNoDelay
(boolean on) Enable/disableTCP_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
Places the input stream for this socket at "end of stream".void
Disables the output stream for this socket.Set
<SocketOption<?>> Returns a set of the socket options supported by this socket.toString()
Converts this socket to aString
.
-
Constructor Details
-
Socket
public Socket()Creates an unconnected Socket.If the application has specified a client socket implementation factory, that factory's createSocketImpl method is called to create the actual socket implementation. Otherwise a system-default socket implementation is created.
- Since:
- 1.1
-
Socket
Creates an unconnected socket, specifying the type of proxy, if any, that should be used regardless of any other settings.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.
- Parameters:
proxy
- aProxy
object specifying what kind of proxying should be used.- Throws:
IllegalArgumentException
- if the proxy is of an invalid type ornull
.- Since:
- 1.5
- See Also:
-
Socket
Creates an unconnected Socket with a user-specified SocketImpl.- Parameters:
impl
- an instance of a SocketImpl the subclass wishes to use on the Socket.- Throws:
SocketException
- if there is an error in the underlying protocol, such as a TCP error.- Since:
- 1.1
-
Socket
Creates a stream socket and connects it to the specified port number on the named host.If the specified host is
null
it is the equivalent of specifying the address asInetAddress.getByName
(null)
. In other words, it is equivalent to specifying an address of the loopback interface.If the application has specified a client socket implementation factory, that factory's createSocketImpl method is called to create the actual socket implementation. Otherwise a system-default socket implementation is created.
- Parameters:
host
- the host name, ornull
for the loopback address.port
- the port number.- Throws:
UnknownHostException
- if the IP address of the host could not be determined.IOException
- if an I/O error occurs when creating the socket.IllegalArgumentException
- if the port parameter is outside the specified range of valid port values, which is between 0 and 65535, inclusive.
-
Socket
Creates a stream socket and connects it to the specified port number at the specified IP address.If the application has specified a client socket implementation factory, that factory's createSocketImpl method is called to create the actual socket implementation. Otherwise a system-default socket implementation is created.
- Parameters:
address
- the IP address.port
- the port number.- Throws:
IOException
- if an I/O error occurs when creating the socket.IllegalArgumentException
- if the port parameter is outside the specified range of valid port values, which is between 0 and 65535, inclusive.NullPointerException
- ifaddress
is null.
-
Socket
Creates a socket and connects it to the specified remote host on the specified remote port. The Socket will also bind() to the local address and port supplied.If the specified host is
null
it is the equivalent of specifying the address asInetAddress.getByName
(null)
. In other words, it is equivalent to specifying an address of the loopback interface.A local port number of
zero
will let the system pick up a free port in thebind
operation.- Parameters:
host
- the name of the remote host, ornull
for the loopback address.port
- the remote portlocalAddr
- the local address the socket is bound to, ornull
for theanyLocal
address.localPort
- the local port the socket is bound to, orzero
for a system selected free port.- Throws:
IOException
- if an I/O error occurs when creating the socket.IllegalArgumentException
- if the port parameter or localPort parameter is outside the specified range of valid port values, which is between 0 and 65535, inclusive.- Since:
- 1.1
-
Socket
public Socket(InetAddress address, int port, InetAddress localAddr, int localPort) throws IOException Creates a socket and connects it to the specified remote address on the specified remote port. The Socket will also bind() to the local address and port supplied.If the specified local address is
null
it is the equivalent of specifying the address as the AnyLocal address (seeInetAddress.isAnyLocalAddress
()
).A local port number of
zero
will let the system pick up a free port in thebind
operation.- Parameters:
address
- the remote addressport
- the remote portlocalAddr
- the local address the socket is bound to, ornull
for theanyLocal
address.localPort
- the local port the socket is bound to orzero
for a system selected free port.- Throws:
IOException
- if an I/O error occurs when creating the socket.IllegalArgumentException
- if the port parameter or localPort parameter is outside the specified range of valid port values, which is between 0 and 65535, inclusive.NullPointerException
- ifaddress
is null.- Since:
- 1.1
-
Socket
@Deprecated(forRemoval=true, since="1.1") public Socket(String host, int port, boolean stream) throws IOException Deprecated, for removal: This API element is subject to removal in a future version.UseDatagramSocket
instead for UDP transport.Creates a stream socket and connects it to the specified port number on the named host.If the specified host is
null
it is the equivalent of specifying the address asInetAddress.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 isfalse
, it creates a datagram socket.If the application has specified a client socket implementation factory, that factory's createSocketImpl method is called to create the actual socket implementation. Otherwise a system-default socket implementation is created.
If a UDP socket is used, TCP/IP related socket options will not apply.
- Parameters:
host
- the host name, ornull
for the loopback address.port
- the port number.stream
- aboolean
indicating whether this is a stream socket or a datagram socket.- Throws:
IOException
- if an I/O error occurs when creating the socket.IllegalArgumentException
- if the port parameter is outside the specified range of valid port values, which is between 0 and 65535, inclusive.
-
Socket
@Deprecated(forRemoval=true, since="1.1") public Socket(InetAddress host, int port, boolean stream) throws IOException Deprecated, for removal: This API element is subject to removal in a future version.UseDatagramSocket
instead for UDP transport.Creates a socket and connects it to the specified port number at the specified IP address.If the stream argument is
true
, this creates a stream socket. If the stream argument isfalse
, it creates a datagram socket.If the application has specified a client socket implementation factory, that factory's createSocketImpl method is called to create the actual socket implementation. Otherwise a system-default socket implementation is created.
If UDP socket is used, TCP/IP related socket options will not apply.
- Parameters:
host
- the IP address.port
- the port number.stream
- iftrue
, create a stream socket; otherwise, create a datagram socket.- Throws:
IOException
- if an I/O error occurs when creating the socket.IllegalArgumentException
- if the port parameter is outside the specified range of valid port values, which is between 0 and 65535, inclusive.NullPointerException
- ifhost
is null.
-
-
Method Details
-
connect
Connects this socket to the server.If the endpoint is an unresolved
InetSocketAddress
, or the connection cannot be established, then the socket is closed, and anIOException
is thrown.This method is interruptible in the following circumstances:
- The socket is associated with
a
SocketChannel
. In that case, interrupting a thread establishing a connection will close the underlying channel and cause this method to throwClosedByInterruptException
with the interrupt status set. - The socket uses the system-default socket implementation and a
virtual thread is establishing a
connection. In that case, interrupting the virtual thread will
cause it to wakeup and close the socket. This method will then throw
SocketException
with the interrupt status set.
- Parameters:
endpoint
- theSocketAddress
- Throws:
IOException
- if an error occurs during the connection, the socket is already connected or the socket is closedUnknownHostException
- if the endpoint is an unresolvedInetSocketAddress
IllegalBlockingModeException
- if this socket has an associated channel, and the channel is in non-blocking modeIllegalArgumentException
- if endpoint is null or is a SocketAddress subclass not supported by this socket- Since:
- 1.4
- The socket is associated with
a
-
connect
Connects this socket to the server with a specified timeout value. A timeout of zero is interpreted as an infinite timeout. The connection will then block until established or an error occurs.If the endpoint is an unresolved
InetSocketAddress
, the connection cannot be established, or the timeout expires before the connection is established, then the socket is closed, and anIOException
is thrown.This method is interruptible in the following circumstances:
- The socket is associated with
a
SocketChannel
. In that case, interrupting a thread establishing a connection will close the underlying channel and cause this method to throwClosedByInterruptException
with the interrupt status set. - The socket uses the system-default socket implementation and a
virtual thread is establishing a
connection. In that case, interrupting the virtual thread will
cause it to wakeup and close the socket. This method will then throw
SocketException
with the interrupt status set.
- Parameters:
endpoint
- theSocketAddress
timeout
- the timeout value to be used in milliseconds.- Throws:
IOException
- if an error occurs during the connection, the socket is already connected or the socket is closedSocketTimeoutException
- if timeout expires before connectingUnknownHostException
- if the endpoint is an unresolvedInetSocketAddress
IllegalBlockingModeException
- if this socket has an associated channel, and the channel is in non-blocking modeIllegalArgumentException
- if endpoint is null or is a SocketAddress subclass not supported by this socket, or iftimeout
is negative- Since:
- 1.4
- The socket is associated with
a
-
bind
Binds the socket to a local address.If the address is
null
, then the system will pick up an ephemeral port and a valid local address to bind the socket.- Parameters:
bindpoint
- theSocketAddress
to bind to- Throws:
IOException
- if the bind operation fails, the socket is already bound or the socket is closed.IllegalArgumentException
- if bindpoint is a SocketAddress subclass not supported by this socket- Since:
- 1.4
- See Also:
-
getInetAddress
Returns the address to which the socket is connected.If the socket was connected prior to being
closed
, then this method will continue to return the connected address after the socket is closed.- Returns:
- the remote IP address to which this socket is connected,
or
null
if the socket is not connected.
-
getLocalAddress
Gets the local address to which the socket is bound.- Returns:
- the local address to which the socket is bound, or the wildcard address if the socket is closed or not bound yet.
- Since:
- 1.1
-
getPort
public int getPort()Returns the remote port number to which this socket is connected.If the socket was connected prior to being
closed
, then this method will continue to return the connected port number after the socket is closed.- Returns:
- the remote port number to which this socket is connected, or 0 if the socket is not connected yet.
-
getLocalPort
public int getLocalPort()Returns the local port number to which this socket is bound.If the socket was bound prior to being
closed
, then this method will continue to return the local port number after the socket is closed.- Returns:
- the local port number to which this socket is bound or -1 if the socket is not bound yet.
-
getRemoteSocketAddress
Returns the address of the endpoint this socket is connected to, ornull
if it is unconnected.If the socket was connected prior to being
closed
, then this method will continue to return the connected address after the socket is closed.- Returns:
- a
SocketAddress
representing the remote endpoint of this socket, ornull
if it is not connected yet. - Since:
- 1.4
- See Also:
-
getLocalSocketAddress
Returns the address of the endpoint this socket is bound to.If a socket bound to an endpoint represented by an
InetSocketAddress
isclosed
, then this method will continue to return anInetSocketAddress
after the socket is closed. In that case the returnedInetSocketAddress
's address is thewildcard
address and its port is the local port that it was bound to.- Returns:
- a
SocketAddress
representing the local endpoint of this socket, ornull
if the socket is not bound yet. - Since:
- 1.4
- See Also:
-
getChannel
Returns the uniqueSocketChannel
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
orServerSocketChannel.accept
methods.- Returns:
- the socket channel associated with this socket,
or
null
if this socket was not created for a channel - Since:
- 1.4
-
getInputStream
Returns an input stream for this socket.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 anIllegalBlockingModeException
.Reading from the input stream is interruptible in the following circumstances:
- The socket is associated with
a
SocketChannel
. In that case, interrupting a thread reading from the input stream will close the underlying channel and cause the read method to throwClosedByInterruptException
with the interrupt status set. - The socket uses the system-default socket implementation and a
virtual thread is reading from the
input stream. In that case, interrupting the virtual thread will
cause it to wakeup and close the socket. The read method will then
throw
SocketException
with the interrupt status set.
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 toread
will throw anIOException
.If there are no bytes buffered on the socket, and the socket has not been closed using
close
, thenavailable
will return0
.
Closing the returned
InputStream
will close the associated socket.- Returns:
- an input stream for reading bytes from this socket.
- Throws:
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 usingshutdownInput()
- The socket is associated with
a
-
getOutputStream
Returns an output stream for this socket.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 anIllegalBlockingModeException
.Writing to the output stream is interruptible in the following circumstances:
- The socket is associated with
a
SocketChannel
. In that case, interrupting a thread writing to the output stream will close the underlying channel and cause the write method to throwClosedByInterruptException
with the interrupt status set. - The socket uses the system-default socket implementation and a
virtual thread is writing to the
output stream. In that case, interrupting the virtual thread will
cause it to wakeup and close the socket. The write method will then
throw
SocketException
with the interrupt status set.
Closing the returned
OutputStream
will close the associated socket.- Returns:
- an output stream for writing bytes to this socket.
- Throws:
IOException
- if an I/O error occurs when creating the output stream, the socket is not connected or the socket is closed.
- The socket is associated with
a
-
setTcpNoDelay
Enable/disableTCP_NODELAY
(disable/enable Nagle's algorithm).- Parameters:
on
-true
to enableTCP_NODELAY
,false
to disable.- Throws:
SocketException
- if there is an error in the underlying protocol, such as a TCP error, or the socket is closed.- Since:
- 1.1
- See Also:
-
getTcpNoDelay
Tests ifTCP_NODELAY
is enabled.- Returns:
- a
boolean
indicating whether or notTCP_NODELAY
is enabled. - Throws:
SocketException
- if there is an error in the underlying protocol, such as a TCP error, or the socket is closed.- Since:
- 1.1
- See Also:
-
setSoLinger
Enable/disableSO_LINGER
with the specified linger time in seconds. The maximum timeout value is platform specific. The setting only affects socket close.- Parameters:
on
- whether or not to linger on.linger
- how long to linger for, if on is true.- Throws:
SocketException
- if there is an error in the underlying protocol, such as a TCP error, or the socket is closed.IllegalArgumentException
- if the linger value is negative.- Since:
- 1.1
- See Also:
-
getSoLinger
Returns setting forSO_LINGER
. -1 returns implies that the option is disabled. The setting only affects socket close.- Returns:
- the setting for
SO_LINGER
. - Throws:
SocketException
- if there is an error in the underlying protocol, such as a TCP error, or the socket is closed.- Since:
- 1.1
- See Also:
-
sendUrgentData
Send one byte of urgent data on the socket. The byte to be sent is the lowest eight bits of the data parameter. The urgent byte is sent after any preceding writes to the socket OutputStream and before any future writes to the OutputStream.- Parameters:
data
- The byte of data to send- Throws:
IOException
- if there is an error sending the data.- Since:
- 1.4
-
setOOBInline
Enable/disableSO_OOBINLINE
(receipt of TCP urgent data) By default, this option is disabled and TCP urgent data received on a socket is silently discarded. If the user wishes to receive urgent data, then this option must be enabled. When enabled, urgent data is received inline with normal 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.
- Parameters:
on
-true
to enableSO_OOBINLINE
,false
to disable.- Throws:
SocketException
- if there is an error in the underlying protocol, such as a TCP error, or the socket is closed.- Since:
- 1.4
- See Also:
-
getOOBInline
Tests ifSO_OOBINLINE
is enabled.- Returns:
- a
boolean
indicating whether or notSO_OOBINLINE
is enabled. - Throws:
SocketException
- if there is an error in the underlying protocol, such as a TCP error, or the socket is closed.- Since:
- 1.4
- See Also:
-
setSoTimeout
Enable/disableSO_TIMEOUT
with the specified timeout, in milliseconds. With this option set to a positive timeout value, a read() call on the InputStream associated with this Socket will block for only this amount of time. If the timeout expires, a java.net.SocketTimeoutException is raised, though the Socket is still valid. A timeout of zero is interpreted as an infinite timeout. The option must be enabled prior to entering the blocking operation to have effect.- Parameters:
timeout
- the specified timeout, in milliseconds.- Throws:
SocketException
- if there is an error in the underlying protocol, such as a TCP error, or the socket is closed.IllegalArgumentException
- iftimeout
is negative- Since:
- 1.1
- See Also:
-
getSoTimeout
Returns setting forSO_TIMEOUT
. 0 returns implies that the option is disabled (i.e., timeout of infinity).- Returns:
- the setting for
SO_TIMEOUT
- Throws:
SocketException
- if there is an error in the underlying protocol, such as a TCP error, or the socket is closed.- Since:
- 1.1
- See Also:
-
setSendBufferSize
Sets theSO_SNDBUF
option to the specified value for thisSocket
. TheSO_SNDBUF
option is used by the platform's networking code as a hint for the size to set the underlying network I/O buffers.Because
SO_SNDBUF
is a hint, applications that want to verify what size the buffers were set to should callgetSendBufferSize()
.- Parameters:
size
- the size to which to set the send buffer size. This value must be greater than 0.- Throws:
SocketException
- if there is an error in the underlying protocol, such as a TCP error, or the socket is closed.IllegalArgumentException
- if the value is 0 or is negative.- Since:
- 1.2
- See Also:
-
getSendBufferSize
Get value of theSO_SNDBUF
option for thisSocket
, that is the buffer size used by the platform for output on thisSocket
.- Returns:
- the value of the
SO_SNDBUF
option for thisSocket
. - Throws:
SocketException
- if there is an error in the underlying protocol, such as a TCP error, or the socket is closed.- Since:
- 1.2
- See Also:
-
setReceiveBufferSize
Sets theSO_RCVBUF
option to the specified value for thisSocket
. TheSO_RCVBUF
option is used by the platform's networking code as a hint for the size to set the underlying network I/O buffers.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 callgetReceiveBufferSize()
.The value of
SO_RCVBUF
is also used to set the TCP receive window that is advertised 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:- For sockets accepted from a ServerSocket, this must be done by calling
ServerSocket.setReceiveBufferSize(int)
before the ServerSocket is bound to a local address. - For client sockets, setReceiveBufferSize() must be called before connecting the socket to its remote peer.
- Parameters:
size
- the size to which to set the receive buffer size. This value must be greater than 0.- Throws:
IllegalArgumentException
- if the value is 0 or is negative.SocketException
- if there is an error in the underlying protocol, such as a TCP error, or the socket is closed.- Since:
- 1.2
- See Also:
- For sockets accepted from a ServerSocket, this must be done by calling
-
getReceiveBufferSize
Gets the value of theSO_RCVBUF
option for thisSocket
, that is the buffer size used by the platform for input on thisSocket
.- Returns:
- the value of the
SO_RCVBUF
option for thisSocket
. - Throws:
SocketException
- if there is an error in the underlying protocol, such as a TCP error, or the socket is closed.- Since:
- 1.2
- See Also:
-
setKeepAlive
Enable/disableSO_KEEPALIVE
.- Parameters:
on
- whether or not to have socket keep alive turned on.- Throws:
SocketException
- if there is an error in the underlying protocol, such as a TCP error, or the socket is closed.- Since:
- 1.3
- See Also:
-
getKeepAlive
Tests ifSO_KEEPALIVE
is enabled.- Returns:
- a
boolean
indicating whether or notSO_KEEPALIVE
is enabled. - Throws:
SocketException
- if there is an error in the underlying protocol, such as a TCP error, or the socket is closed.- Since:
- 1.3
- See Also:
-
setTrafficClass
Sets traffic class or type-of-service octet in the IP header for packets sent from this Socket. As the underlying network implementation may ignore this value applications should consider it a hint.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
integer
, the least significant 8 bits of which represent the value of the TOS octet in IP packets sent by the socket. RFC 1349 defines the TOS values as follows: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.- Parameters:
tc
- anint
value for the bitset.- Throws:
SocketException
- if there is an error setting the traffic class or type-of-service, or the socket is closed.- Since:
- 1.4
- See Also:
-
getTrafficClass
Gets traffic class or type-of-service in the IP header for packets sent from this SocketAs 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 thesetTrafficClass(int)
method on this Socket.- Returns:
- the traffic class or type-of-service already set
- Throws:
SocketException
- if there is an error obtaining the traffic class or type-of-service value, or the socket is closed.- Since:
- 1.4
- See Also:
-
setReuseAddress
Enable/disable theSO_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 or2MSL
wait state). For applications using a well known socket address or port it may not be possible to bind a socket to the requiredSocketAddress
if there is a connection in the timeout state involving the socket address or port.Enabling
SO_REUSEADDR
prior to binding the socket usingbind(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 ofSO_REUSEADDR
is disabled.The behaviour when
SO_REUSEADDR
is enabled or disabled after a socket is bound (SeeisBound()
) is not defined.- Parameters:
on
- whether to enable or disable the socket option- Throws:
SocketException
- if an error occurs enabling or disabling theSO_REUSEADDR
socket option, or the socket is closed.- Since:
- 1.4
- See Also:
-
getReuseAddress
Tests ifSO_REUSEADDR
is enabled.- Returns:
- a
boolean
indicating whether or notSO_REUSEADDR
is enabled. - Throws:
SocketException
- if there is an error in the underlying protocol, such as a TCP error, or the socket is closed.- Since:
- 1.4
- See Also:
-
close
Closes this socket.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) and several of the methods defined by this class will throw an exception if invoked on the closed socket. A new socket needs to be created.
Closing this socket will also close the socket's
InputStream
andOutputStream
.If this socket has an associated channel then the channel is closed as well.
- Specified by:
close
in interfaceAutoCloseable
- Specified by:
close
in interfaceCloseable
- Throws:
IOException
- if an I/O error occurs when closing this socket.- See Also:
-
shutdownInput
Places the input stream for this socket at "end of stream". Any data sent to the input stream side of the socket is acknowledged and then silently discarded.If you read from a socket input stream after invoking this method on the socket, the stream's
available
method will return 0, and itsread
methods will return-1
(end of stream).- Throws:
IOException
- if an I/O error occurs when shutting down this socket, the socket is not connected or the socket is closed.- Since:
- 1.3
- See Also:
-
shutdownOutput
Disables the output stream for this socket. For a TCP socket, any previously written data will be sent followed by TCP's normal connection termination sequence. If you write to a socket output stream after invoking shutdownOutput() on the socket, the stream will throw an IOException.- Throws:
IOException
- if an I/O error occurs when shutting down this socket, the socket is not connected or the socket is closed.- Since:
- 1.3
- See Also:
-
toString
-
isConnected
public boolean isConnected()Returns the connection state of the socket.Note: Closing a socket doesn't clear its connection state, which means this method will return
true
for a closed socket (seeisClosed()
) if it was successfully connected prior to being closed.- Returns:
- true if the socket was successfully connected to a server
- Since:
- 1.4
-
isBound
public boolean isBound()Returns the binding state of the socket.Note: Closing a socket doesn't clear its binding state, which means this method will return
true
for a closed socket (seeisClosed()
) if it was successfully bound prior to being closed.- Returns:
- true if the socket was successfully bound to an address
- Since:
- 1.4
- See Also:
-
isClosed
public boolean isClosed()Returns the closed state of the socket.- Returns:
- true if the socket has been closed
- Since:
- 1.4
- See Also:
-
isInputShutdown
public boolean isInputShutdown()Returns whether the read-half of the socket connection is closed.- Returns:
- true if the input of the socket has been shutdown
- Since:
- 1.4
- See Also:
-
isOutputShutdown
public boolean isOutputShutdown()Returns whether the write-half of the socket connection is closed.- Returns:
- true if the output of the socket has been shutdown
- Since:
- 1.4
- See Also:
-
setSocketImplFactory
@Deprecated(since="17") public static void setSocketImplFactory(SocketImplFactory fac) throws IOException Deprecated.Use aSocketFactory
and subclassSocket
directly.
This method provided a way in early JDK releases to replace the system wide implementation ofSocket
. It has been mostly obsolete since Java 1.4. If required, aSocket
can be created to use a custom implementation by extendingSocket
and using the protected constructor that takes an implementation as a parameter.Sets the client socket implementation factory for the application. The factory can be specified only once.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.- Parameters:
fac
- the desired factory.- Throws:
IOException
- if an I/O error occurs when setting the socket factory.SocketException
- if the factory is already defined.- See Also:
-
setPerformancePreferences
public void setPerformancePreferences(int connectionTime, int latency, int bandwidth) Sets performance preferences for this socket.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.
- Parameters:
connectionTime
- Anint
expressing the relative importance of a short connection timelatency
- Anint
expressing the relative importance of low latencybandwidth
- Anint
expressing the relative importance of high bandwidth- Since:
- 1.5
-
setOption
Sets the value of a socket option.- Type Parameters:
T
- The type of the socket option value- Parameters:
name
- The socket optionvalue
- The value of the socket option. A value ofnull
may be valid for some options.- Returns:
- this Socket
- Throws:
UnsupportedOperationException
- if the socket does not support the option.IllegalArgumentException
- if the value is not valid for the option.IOException
- if an I/O error occurs, or if the socket is closed.NullPointerException
- if name isnull
- Since:
- 9
-
getOption
Returns the value of a socket option.- Type Parameters:
T
- The type of the socket option value- Parameters:
name
- The socket option- Returns:
- The value of the socket option.
- Throws:
UnsupportedOperationException
- if the socket does not support the option.IOException
- if an I/O error occurs, or if the socket is closed.NullPointerException
- if name isnull
- Since:
- 9
-
supportedOptions
Returns a set of the socket options supported by this socket. This method will continue to return the set of options even after the socket has been closed.- Returns:
- A set of the socket options supported by this socket. This set may be empty if the socket's SocketImpl cannot be created.
- Since:
- 9
-
DatagramSocket
instead for UDP transport.