- java.lang.Object
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- java.net.Socket
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- All Implemented Interfaces:
Closeable,AutoCloseable
- Direct Known Subclasses:
SSLSocket
public class Socket extends Object implements Closeable
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
SocketImplclass. An application, by changing the socket factory that creates the socket implementation, can configure itself to create sockets appropriate to the local firewall.- Since:
- 1.0
- See Also:
setSocketImplFactory(java.net.SocketImplFactory),SocketImpl,SocketChannel
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Constructor Summary
Constructors Modifier Constructor Description Socket()Creates an unconnected socket, with the system-default type of 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.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.protectedSocket(SocketImpl impl)Creates an unconnected Socket with a user-specified SocketImpl.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description voidbind(SocketAddress bindpoint)Binds the socket to a local address.voidclose()Closes this socket.voidconnect(SocketAddress endpoint)Connects this socket to the server.voidconnect(SocketAddress endpoint, int timeout)Connects this socket to the server with a specified timeout value.SocketChannelgetChannel()Returns the uniqueSocketChannelobject associated with this socket, if any.InetAddressgetInetAddress()Returns the address to which the socket is connected.InputStreamgetInputStream()Returns an input stream for this socket.booleangetKeepAlive()Tests ifSO_KEEPALIVEis enabled.InetAddressgetLocalAddress()Gets the local address to which the socket is bound.intgetLocalPort()Returns the local port number to which this socket is bound.SocketAddressgetLocalSocketAddress()Returns the address of the endpoint this socket is bound to.booleangetOOBInline()Tests ifSO_OOBINLINEis enabled.<T> TgetOption(SocketOption<T> name)Returns the value of a socket option.OutputStreamgetOutputStream()Returns an output stream for this socket.intgetPort()Returns the remote port number to which this socket is connected.intgetReceiveBufferSize()Gets the value of theSO_RCVBUFoption for thisSocket, that is the buffer size used by the platform for input on thisSocket.SocketAddressgetRemoteSocketAddress()Returns the address of the endpoint this socket is connected to, ornullif it is unconnected.booleangetReuseAddress()Tests ifSO_REUSEADDRis enabled.intgetSendBufferSize()Get value of theSO_SNDBUFoption for thisSocket, that is the buffer size used by the platform for output on thisSocket.intgetSoLinger()Returns setting forSO_LINGER.intgetSoTimeout()Returns setting forSO_TIMEOUT. 0 returns implies that the option is disabled (i.e., timeout of infinity).booleangetTcpNoDelay()Tests ifTCP_NODELAYis enabled.intgetTrafficClass()Gets traffic class or type-of-service in the IP header for packets sent from this SocketbooleanisBound()Returns the binding state of the socket.booleanisClosed()Returns the closed state of the socket.booleanisConnected()Returns the connection state of the socket.booleanisInputShutdown()Returns whether the read-half of the socket connection is closed.booleanisOutputShutdown()Returns whether the write-half of the socket connection is closed.voidsendUrgentData(int data)Send one byte of urgent data on the socket.voidsetKeepAlive(boolean on)Enable/disableSO_KEEPALIVE.voidsetOOBInline(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> SocketsetOption(SocketOption<T> name, T value)Sets the value of a socket option.voidsetPerformancePreferences(int connectionTime, int latency, int bandwidth)Sets performance preferences for this socket.voidsetReceiveBufferSize(int size)Sets theSO_RCVBUFoption to the specified value for thisSocket.voidsetReuseAddress(boolean on)Enable/disable theSO_REUSEADDRsocket option.voidsetSendBufferSize(int size)Sets theSO_SNDBUFoption to the specified value for thisSocket.static voidsetSocketImplFactory(SocketImplFactory fac)Sets the client socket implementation factory for the application.voidsetSoLinger(boolean on, int linger)Enable/disableSO_LINGERwith the specified linger time in seconds.voidsetSoTimeout(int timeout)Enable/disableSO_TIMEOUTwith the specified timeout, in milliseconds.voidsetTcpNoDelay(boolean on)Enable/disableTCP_NODELAY(disable/enable Nagle's algorithm).voidsetTrafficClass(int tc)Sets traffic class or type-of-service octet in the IP header for packets sent from this Socket.voidshutdownInput()Places the input stream for this socket at "end of stream".voidshutdownOutput()Disables the output stream for this socket.Set<SocketOption<?>>supportedOptions()Returns a set of the socket options supported by this socket.StringtoString()Converts this socket to aString.
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Constructor Detail
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Socket
public Socket()
Creates an unconnected socket, with the system-default type of SocketImpl.- Since:
- 1.1
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Socket
public Socket(Proxy proxy)
Creates an unconnected socket, specifying the type of proxy, if any, that should be used regardless of any other settings.If there is a security manager, its
checkConnectmethod 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.
- Parameters:
proxy- aProxyobject specifying what kind of proxying should be used.- Throws:
IllegalArgumentException- if the proxy is of an invalid type ornull.SecurityException- if a security manager is present and permission to connect to the proxy is denied.- Since:
- 1.5
- See Also:
ProxySelector,Proxy
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Socket
protected Socket(SocketImpl impl) throws SocketException
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.SecurityException- ifimplis non-null and a security manager is set and itscheckPermissionmethod doesn't allowNetPermission("setSocketImpl").- Since:
- 1.1
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Socket
public Socket(String host, int port) throws UnknownHostException, IOException
Creates a stream socket and connects it to the specified port number on the named host.If the specified host is
nullit 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 server socket factory, that factory's
createSocketImplmethod is called to create the actual socket implementation. Otherwise a "plain" socket is created.If there is a security manager, its
checkConnectmethod is called with the host address andportas its arguments. This could result in a SecurityException.- Parameters:
host- the host name, ornullfor 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.SecurityException- if a security manager exists and itscheckConnectmethod doesn't allow the operation.IllegalArgumentException- if the port parameter is outside the specified range of valid port values, which is between 0 and 65535, inclusive.- See Also:
setSocketImplFactory(java.net.SocketImplFactory),SocketImpl,SocketImplFactory.createSocketImpl(),SecurityManager.checkConnect(java.lang.String, int)
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Socket
public Socket(InetAddress address, int port) throws IOException
Creates a stream socket and connects it to the specified port number at the specified IP address.If the application has specified a socket factory, that factory's
createSocketImplmethod is called to create the actual socket implementation. Otherwise a "plain" socket is created.If there is a security manager, its
checkConnectmethod is called with the host address andportas its arguments. This could result in a SecurityException.- Parameters:
address- the IP address.port- the port number.- Throws:
IOException- if an I/O error occurs when creating the socket.SecurityException- if a security manager exists and itscheckConnectmethod doesn't allow the operation.IllegalArgumentException- if the port parameter is outside the specified range of valid port values, which is between 0 and 65535, inclusive.NullPointerException- ifaddressis null.- See Also:
setSocketImplFactory(java.net.SocketImplFactory),SocketImpl,SocketImplFactory.createSocketImpl(),SecurityManager.checkConnect(java.lang.String, int)
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Socket
public Socket(String host, int port, InetAddress localAddr, int localPort) throws IOException
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
nullit 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
zerowill let the system pick up a free port in thebindoperation.If there is a security manager, its
checkConnectmethod is called with the host address andportas its arguments. This could result in a SecurityException.- Parameters:
host- the name of the remote host, ornullfor the loopback address.port- the remote portlocalAddr- the local address the socket is bound to, ornullfor theanyLocaladdress.localPort- the local port the socket is bound to, orzerofor a system selected free port.- Throws:
IOException- if an I/O error occurs when creating the socket.SecurityException- if a security manager exists and itscheckConnectmethod doesn't allow the connection to the destination, or if itscheckListenmethod doesn't allow the bind to the local port.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
- See Also:
SecurityManager.checkConnect(java.lang.String, int)
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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
nullit is the equivalent of specifying the address as the AnyLocal address (seeInetAddress.isAnyLocalAddress()).A local port number of
zerowill let the system pick up a free port in thebindoperation.If there is a security manager, its
checkConnectmethod is called with the host address andportas its arguments. This could result in a SecurityException.- Parameters:
address- the remote addressport- the remote portlocalAddr- the local address the socket is bound to, ornullfor theanyLocaladdress.localPort- the local port the socket is bound to orzerofor a system selected free port.- Throws:
IOException- if an I/O error occurs when creating the socket.SecurityException- if a security manager exists and itscheckConnectmethod doesn't allow the connection to the destination, or if itscheckListenmethod doesn't allow the bind to the local port.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- ifaddressis null.- Since:
- 1.1
- See Also:
SecurityManager.checkConnect(java.lang.String, int)
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Socket
@Deprecated public Socket(String host, int port, boolean stream) throws IOException
Deprecated.Use DatagramSocket 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
nullit 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 server socket factory, that factory's
createSocketImplmethod is called to create the actual socket implementation. Otherwise a "plain" socket is created.If there is a security manager, its
checkConnectmethod is called with the host address andportas its arguments. This could result in a SecurityException.If a UDP socket is used, TCP/IP related socket options will not apply.
- Parameters:
host- the host name, ornullfor the loopback address.port- the port number.stream- abooleanindicating whether this is a stream socket or a datagram socket.- Throws:
IOException- if an I/O error occurs when creating the socket.SecurityException- if a security manager exists and itscheckConnectmethod doesn't allow the operation.IllegalArgumentException- if the port parameter is outside the specified range of valid port values, which is between 0 and 65535, inclusive.- See Also:
setSocketImplFactory(java.net.SocketImplFactory),SocketImpl,SocketImplFactory.createSocketImpl(),SecurityManager.checkConnect(java.lang.String, int)
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Socket
@Deprecated public Socket(InetAddress host, int port, boolean stream) throws IOException
Deprecated.Use DatagramSocket 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 server socket factory, that factory's
createSocketImplmethod is called to create the actual socket implementation. Otherwise a "plain" socket is created.If there is a security manager, its
checkConnectmethod is called withhost.getHostAddress()andportas its arguments. This could result in a SecurityException.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.SecurityException- if a security manager exists and itscheckConnectmethod doesn't allow the operation.IllegalArgumentException- if the port parameter is outside the specified range of valid port values, which is between 0 and 65535, inclusive.NullPointerException- ifhostis null.- See Also:
setSocketImplFactory(java.net.SocketImplFactory),SocketImpl,SocketImplFactory.createSocketImpl(),SecurityManager.checkConnect(java.lang.String, int)
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Method Detail
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connect
public void connect(SocketAddress endpoint) throws IOException
Connects this socket to the server.- Parameters:
endpoint- theSocketAddress- Throws:
IOException- if an error occurs during the connectionIllegalBlockingModeException- 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
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connect
public void connect(SocketAddress endpoint, int timeout) throws IOException
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.- Parameters:
endpoint- theSocketAddresstimeout- the timeout value to be used in milliseconds.- Throws:
IOException- if an error occurs during the connectionSocketTimeoutException- if timeout expires before connectingIllegalBlockingModeException- 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
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bind
public void bind(SocketAddress bindpoint) throws IOException
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- theSocketAddressto bind to- Throws:
IOException- if the bind operation fails, or if the socket is already bound.IllegalArgumentException- if bindpoint is a SocketAddress subclass not supported by this socketSecurityException- if a security manager exists and itscheckListenmethod doesn't allow the bind to the local port.- Since:
- 1.4
- See Also:
isBound()
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getInetAddress
public InetAddress 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
nullif the socket is not connected.
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getLocalAddress
public InetAddress getLocalAddress()
Gets the local address to which the socket is bound.If there is a security manager set, its
checkConnectmethod is called with the local address and-1as its arguments to see if the operation is allowed. If the operation is not allowed, theloopbackaddress is returned.- Returns:
- the local address to which the socket is bound, the loopback address if denied by the security manager, or the wildcard address if the socket is closed or not bound yet.
- Since:
- 1.1
- See Also:
SecurityManager.checkConnect(java.lang.String, int)
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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.
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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.
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getRemoteSocketAddress
public SocketAddress getRemoteSocketAddress()
Returns the address of the endpoint this socket is connected to, ornullif 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
SocketAddressrepresenting the remote endpoint of this socket, ornullif it is not connected yet. - Since:
- 1.4
- See Also:
getInetAddress(),getPort(),connect(SocketAddress, int),connect(SocketAddress)
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getLocalSocketAddress
public SocketAddress getLocalSocketAddress()
Returns the address of the endpoint this socket is bound to.If a socket bound to an endpoint represented by an
InetSocketAddressisclosed, then this method will continue to return anInetSocketAddressafter the socket is closed. In that case the returnedInetSocketAddress's address is thewildcardaddress and its port is the local port that it was bound to.If there is a security manager set, its
checkConnectmethod is called with the local address and-1as its arguments to see if the operation is allowed. If the operation is not allowed, aSocketAddressrepresenting theloopbackaddress and the local port to which this socket is bound is returned.- Returns:
- a
SocketAddressrepresenting the local endpoint of this socket, or aSocketAddressrepresenting the loopback address if denied by the security manager, ornullif the socket is not bound yet. - Since:
- 1.4
- See Also:
getLocalAddress(),getLocalPort(),bind(SocketAddress),SecurityManager.checkConnect(java.lang.String, int)
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getChannel
public SocketChannel getChannel()
Returns the uniqueSocketChannelobject associated with this socket, if any.A socket will have a channel if, and only if, the channel itself was created via the
SocketChannel.openorServerSocketChannel.acceptmethods.- Returns:
- the socket channel associated with this socket,
or
nullif this socket was not created for a channel - Since:
- 1.4
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getInputStream
public InputStream getInputStream() throws IOException
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
readoperations will throw anIllegalBlockingModeException.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 toreadwill throw anIOException.If there are no bytes buffered on the socket, and the socket has not been closed using
close, thenavailablewill return0.
Closing the returned
InputStreamwill 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()
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getOutputStream
public OutputStream getOutputStream() throws IOException
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
writeoperations will throw anIllegalBlockingModeException.Closing the returned
OutputStreamwill 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 or if the socket is not connected.
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setTcpNoDelay
public void setTcpNoDelay(boolean on) throws SocketExceptionEnable/disableTCP_NODELAY(disable/enable Nagle's algorithm).- Parameters:
on-trueto enable TCP_NODELAY,falseto disable.- Throws:
SocketException- if there is an error in the underlying protocol, such as a TCP error.- Since:
- 1.1
- See Also:
getTcpNoDelay()
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getTcpNoDelay
public boolean getTcpNoDelay() throws SocketExceptionTests ifTCP_NODELAYis enabled.- Returns:
- a
booleanindicating whether or notTCP_NODELAYis enabled. - Throws:
SocketException- if there is an error in the underlying protocol, such as a TCP error.- Since:
- 1.1
- See Also:
setTcpNoDelay(boolean)
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setSoLinger
public void setSoLinger(boolean on, int linger) throws SocketExceptionEnable/disableSO_LINGERwith 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.IllegalArgumentException- if the linger value is negative.- Since:
- 1.1
- See Also:
getSoLinger()
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getSoLinger
public int getSoLinger() throws SocketExceptionReturns 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.- Since:
- 1.1
- See Also:
setSoLinger(boolean, int)
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sendUrgentData
public void sendUrgentData(int data) throws IOExceptionSend 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
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setOOBInline
public void setOOBInline(boolean on) throws SocketExceptionEnable/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-trueto enableSO_OOBINLINE,falseto disable.- Throws:
SocketException- if there is an error in the underlying protocol, such as a TCP error.- Since:
- 1.4
- See Also:
getOOBInline()
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getOOBInline
public boolean getOOBInline() throws SocketExceptionTests ifSO_OOBINLINEis enabled.- Returns:
- a
booleanindicating whether or notSO_OOBINLINEis enabled. - Throws:
SocketException- if there is an error in the underlying protocol, such as a TCP error.- Since:
- 1.4
- See Also:
setOOBInline(boolean)
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setSoTimeout
public void setSoTimeout(int timeout) throws SocketExceptionEnable/disableSO_TIMEOUTwith the specified timeout, in milliseconds. With this option set to a non-zero timeout, 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. 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.- Since:
- 1.1
- See Also:
getSoTimeout()
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getSoTimeout
public int getSoTimeout() throws SocketExceptionReturns 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.- Since:
- 1.1
- See Also:
setSoTimeout(int)
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setSendBufferSize
public void setSendBufferSize(int size) throws SocketExceptionSets theSO_SNDBUFoption to the specified value for thisSocket. TheSO_SNDBUFoption is used by the platform's networking code as a hint for the size to set the underlying network I/O buffers.Because
SO_SNDBUFis 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.IllegalArgumentException- if the value is 0 or is negative.- Since:
- 1.2
- See Also:
getSendBufferSize()
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getSendBufferSize
public int getSendBufferSize() throws SocketExceptionGet value of theSO_SNDBUFoption for thisSocket, that is the buffer size used by the platform for output on thisSocket.- Returns:
- the value of the
SO_SNDBUFoption for thisSocket. - Throws:
SocketException- if there is an error in the underlying protocol, such as a TCP error.- Since:
- 1.2
- See Also:
setSendBufferSize(int)
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setReceiveBufferSize
public void setReceiveBufferSize(int size) throws SocketExceptionSets theSO_RCVBUFoption to the specified value for thisSocket. TheSO_RCVBUFoption 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_RCVBUFis a hint, applications that want to verify what size the buffers were set to should callgetReceiveBufferSize().The value of
SO_RCVBUFis 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:- 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.- Since:
- 1.2
- See Also:
getReceiveBufferSize(),ServerSocket.setReceiveBufferSize(int)
- For sockets accepted from a ServerSocket, this must be done by calling
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getReceiveBufferSize
public int getReceiveBufferSize() throws SocketExceptionGets the value of theSO_RCVBUFoption for thisSocket, that is the buffer size used by the platform for input on thisSocket.- Returns:
- the value of the
SO_RCVBUFoption for thisSocket. - Throws:
SocketException- if there is an error in the underlying protocol, such as a TCP error.- Since:
- 1.2
- See Also:
setReceiveBufferSize(int)
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setKeepAlive
public void setKeepAlive(boolean on) throws SocketExceptionEnable/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.- Since:
- 1.3
- See Also:
getKeepAlive()
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getKeepAlive
public boolean getKeepAlive() throws SocketExceptionTests ifSO_KEEPALIVEis enabled.- Returns:
- a
booleanindicating whether or notSO_KEEPALIVEis enabled. - Throws:
SocketException- if there is an error in the underlying protocol, such as a TCP error.- Since:
- 1.3
- See Also:
setKeepAlive(boolean)
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setTrafficClass
public void setTrafficClass(int tc) throws SocketExceptionSets 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 <= 255or 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
tcis the value that would be placed into the sin6_flowinfo field of the IP header.- Parameters:
tc- anintvalue for the bitset.- Throws:
SocketException- if there is an error setting the traffic class or type-of-service- Since:
- 1.4
- See Also:
getTrafficClass(),SocketOptions.IP_TOS
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getTrafficClass
public int getTrafficClass() throws SocketExceptionGets 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.- Since:
- 1.4
- See Also:
setTrafficClass(int),SocketOptions.IP_TOS
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setReuseAddress
public void setReuseAddress(boolean on) throws SocketExceptionEnable/disable theSO_REUSEADDRsocket 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_WAITstate or2MSLwait state). For applications using a well known socket address or port it may not be possible to bind a socket to the requiredSocketAddressif there is a connection in the timeout state involving the socket address or port.Enabling
SO_REUSEADDRprior to binding the socket usingbind(SocketAddress)allows the socket to be bound even though a previous connection is in a timeout state.When a
Socketis created the initial setting ofSO_REUSEADDRis disabled.The behaviour when
SO_REUSEADDRis 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_REUSEADDRsocket option, or the socket is closed.- Since:
- 1.4
- See Also:
getReuseAddress(),bind(SocketAddress),isClosed(),isBound()
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getReuseAddress
public boolean getReuseAddress() throws SocketExceptionTests ifSO_REUSEADDRis enabled.- Returns:
- a
booleanindicating whether or notSO_REUSEADDRis enabled. - Throws:
SocketException- if there is an error in the underlying protocol, such as a TCP error.- Since:
- 1.4
- See Also:
setReuseAddress(boolean)
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close
public void close() throws IOExceptionCloses 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). A new socket needs to be created.
Closing this socket will also close the socket's
InputStreamandOutputStream.If this socket has an associated channel then the channel is closed as well.
- Specified by:
closein interfaceAutoCloseable- Specified by:
closein interfaceCloseable- Throws:
IOException- if an I/O error occurs when closing this socket.- See Also:
isClosed()
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shutdownInput
public void shutdownInput() throws IOExceptionPlaces 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
availablemethod will return 0, and itsreadmethods will return-1(end of stream).- Throws:
IOException- if an I/O error occurs when shutting down this socket.- Since:
- 1.3
- See Also:
shutdownOutput(),close(),setSoLinger(boolean, int),isInputShutdown()
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shutdownOutput
public void shutdownOutput() throws IOExceptionDisables 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.- Since:
- 1.3
- See Also:
shutdownInput(),close(),setSoLinger(boolean, int),isOutputShutdown()
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toString
public String toString()
Converts this socket to aString.
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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
truefor a closed socket (seeisClosed()) if it was successfuly connected prior to being closed.- Returns:
- true if the socket was successfuly connected to a server
- Since:
- 1.4
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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
truefor a closed socket (seeisClosed()) if it was successfuly bound prior to being closed.- Returns:
- true if the socket was successfuly bound to an address
- Since:
- 1.4
- See Also:
bind(java.net.SocketAddress)
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isClosed
public boolean isClosed()
Returns the closed state of the socket.- Returns:
- true if the socket has been closed
- Since:
- 1.4
- See Also:
close()
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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:
shutdownInput()
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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:
shutdownOutput()
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setSocketImplFactory
public static void setSocketImplFactory(SocketImplFactory fac) throws IOException
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
createSocketImplmethod is called to create the actual socket implementation.Passing
nullto 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
checkSetFactorymethod 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 is already defined.SecurityException- if a security manager exists and itscheckSetFactorymethod doesn't allow the operation.- See Also:
SocketImplFactory.createSocketImpl(),SecurityManager.checkSetFactory()
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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- Anintexpressing the relative importance of a short connection timelatency- Anintexpressing the relative importance of low latencybandwidth- Anintexpressing the relative importance of high bandwidth- Since:
- 1.5
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setOption
public <T> Socket setOption(SocketOption<T> name, T value) throws IOException
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 ofnullmay 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 isnullSecurityException- if a security manager is set and if the socket option requires a security permission and if the caller does not have the required permission.StandardSocketOptionsdo not require any security permission.- Since:
- 9
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getOption
public <T> T getOption(SocketOption<T> name) throws IOException
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 isnullSecurityException- if a security manager is set and if the socket option requires a security permission and if the caller does not have the required permission.StandardSocketOptionsdo not require any security permission.- Since:
- 9
-
supportedOptions
public Set<SocketOption<?>> 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
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