The SocketOptions.java Java example source code
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package java.net;
import java.lang.annotation.Native;
/**
* Interface of methods to get/set socket options. This interface is
* implemented by: <B>SocketImpl and DatagramSocketImpl.
* Subclasses of these should override the methods
* of this interface in order to support their own options.
* <P>
* The methods and constants which specify options in this interface are
* for implementation only. If you're not subclassing SocketImpl or
* DatagramSocketImpl, <B>you won't use these directly. There are
* type-safe methods to get/set each of these options in Socket, ServerSocket,
* DatagramSocket and MulticastSocket.
* <P>
* @author David Brown
*/
public interface SocketOptions {
/**
* Enable/disable the option specified by <I>optID. If the option
* is to be enabled, and it takes an option-specific "value", this is
* passed in <I>value. The actual type of value is option-specific,
* and it is an error to pass something that isn't of the expected type:
* <BR>
* SocketImpl s;
* ...
* s.setOption(SO_LINGER, new Integer(10));
* // OK - set SO_LINGER w/ timeout of 10 sec.
* s.setOption(SO_LINGER, new Double(10));
* // ERROR - expects java.lang.Integer
*</PRE>
* If the requested option is binary, it can be set using this method by
* a java.lang.Boolean:
* <BR>
* s.setOption(TCP_NODELAY, new Boolean(true));
* // OK - enables TCP_NODELAY, a binary option
* </PRE>
* <BR>
* Any option can be disabled using this method with a Boolean(false):
* <BR>
* s.setOption(TCP_NODELAY, new Boolean(false));
* // OK - disables TCP_NODELAY
* s.setOption(SO_LINGER, new Boolean(false));
* // OK - disables SO_LINGER
* </PRE>
* <BR>
* For an option that has a notion of on and off, and requires
* a non-boolean parameter, setting its value to anything other than
* <I>Boolean(false) implicitly enables it.
* <BR>
* Throws SocketException if the option is unrecognized,
* the socket is closed, or some low-level error occurred
* <BR>
* @param optID identifies the option
* @param value the parameter of the socket option
* @throws SocketException if the option is unrecognized,
* the socket is closed, or some low-level error occurred
* @see #getOption(int)
*/
public void
setOption(int optID, Object value) throws SocketException;
/**
* Fetch the value of an option.
* Binary options will return java.lang.Boolean(true)
* if enabled, java.lang.Boolean(false) if disabled, e.g.:
* <BR>
* SocketImpl s;
* ...
* Boolean noDelay = (Boolean)(s.getOption(TCP_NODELAY));
* if (noDelay.booleanValue()) {
* // true if TCP_NODELAY is enabled...
* ...
* }
* </PRE>
* <P>
* For options that take a particular type as a parameter,
* getOption(int) will return the parameter's value, else
* it will return java.lang.Boolean(false):
* <PRE>
* Object o = s.getOption(SO_LINGER);
* if (o instanceof Integer) {
* System.out.print("Linger time is " + ((Integer)o).intValue());
* } else {
* // the true type of o is java.lang.Boolean(false);
* }
* </PRE>
*
* @param optID an {@code int} identifying the option to fetch
* @return the value of the option
* @throws SocketException if the socket is closed
* @throws SocketException if <I>optID is unknown along the
* protocol stack (including the SocketImpl)
* @see #setOption(int, java.lang.Object)
*/
public Object getOption(int optID) throws SocketException;
/**
* The java-supported BSD-style options.
*/
/**
* Disable Nagle's algorithm for this connection. Written data
* to the network is not buffered pending acknowledgement of
* previously written data.
*<P>
* Valid for TCP only: SocketImpl.
*
* @see Socket#setTcpNoDelay
* @see Socket#getTcpNoDelay
*/
@Native public final static int TCP_NODELAY = 0x0001;
/**
* Fetch the local address binding of a socket (this option cannot
* be "set" only "gotten", since sockets are bound at creation time,
* and so the locally bound address cannot be changed). The default local
* address of a socket is INADDR_ANY, meaning any local address on a
* multi-homed host. A multi-homed host can use this option to accept
* connections to only one of its addresses (in the case of a
* ServerSocket or DatagramSocket), or to specify its return address
* to the peer (for a Socket or DatagramSocket). The parameter of
* this option is an InetAddress.
* <P>
* This option <B>must be specified in the constructor.
* <P>
* Valid for: SocketImpl, DatagramSocketImpl
*
* @see Socket#getLocalAddress
* @see DatagramSocket#getLocalAddress
*/
@Native public final static int SO_BINDADDR = 0x000F;
/** Sets SO_REUSEADDR for a socket. This is used only for MulticastSockets
* in java, and it is set by default for MulticastSockets.
* <P>
* Valid for: DatagramSocketImpl
*/
@Native public final static int SO_REUSEADDR = 0x04;
/**
* Sets SO_BROADCAST for a socket. This option enables and disables
* the ability of the process to send broadcast messages. It is supported
* for only datagram sockets and only on networks that support
* the concept of a broadcast message (e.g. Ethernet, token ring, etc.),
* and it is set by default for DatagramSockets.
* @since 1.4
*/
@Native public final static int SO_BROADCAST = 0x0020;
/** Set which outgoing interface on which to send multicast packets.
* Useful on hosts with multiple network interfaces, where applications
* want to use other than the system default. Takes/returns an InetAddress.
* <P>
* Valid for Multicast: DatagramSocketImpl
*
* @see MulticastSocket#setInterface(InetAddress)
* @see MulticastSocket#getInterface()
*/
@Native public final static int IP_MULTICAST_IF = 0x10;
/** Same as above. This option is introduced so that the behaviour
* with IP_MULTICAST_IF will be kept the same as before, while
* this new option can support setting outgoing interfaces with either
* IPv4 and IPv6 addresses.
*
* NOTE: make sure there is no conflict with this
* @see MulticastSocket#setNetworkInterface(NetworkInterface)
* @see MulticastSocket#getNetworkInterface()
* @since 1.4
*/
@Native public final static int IP_MULTICAST_IF2 = 0x1f;
/**
* This option enables or disables local loopback of multicast datagrams.
* This option is enabled by default for Multicast Sockets.
* @since 1.4
*/
@Native public final static int IP_MULTICAST_LOOP = 0x12;
/**
* This option sets the type-of-service or traffic class field
* in the IP header for a TCP or UDP socket.
* @since 1.4
*/
@Native public final static int IP_TOS = 0x3;
/**
* Specify a linger-on-close timeout. This option disables/enables
* immediate return from a <B>close() of a TCP Socket. Enabling
* this option with a non-zero Integer <I>timeout means that a
* <B>close() will block pending the transmission and acknowledgement
* of all data written to the peer, at which point the socket is closed
* <I>gracefully. Upon reaching the linger timeout, the socket is
* closed <I>forcefully, with a TCP RST. Enabling the option with a
* timeout of zero does a forceful close immediately. If the specified
* timeout value exceeds 65,535 it will be reduced to 65,535.
* <P>
* Valid only for TCP: SocketImpl
*
* @see Socket#setSoLinger
* @see Socket#getSoLinger
*/
@Native public final static int SO_LINGER = 0x0080;
/** Set a timeout on blocking Socket operations:
* <PRE>
* ServerSocket.accept();
* SocketInputStream.read();
* DatagramSocket.receive();
* </PRE>
*
* <P> The option must be set prior to entering a blocking
* operation to take effect. If the timeout expires and the
* operation would continue to block,
* <B>java.io.InterruptedIOException is raised. The Socket is
* not closed in this case.
*
* <P> Valid for all sockets: SocketImpl, DatagramSocketImpl
*
* @see Socket#setSoTimeout
* @see ServerSocket#setSoTimeout
* @see DatagramSocket#setSoTimeout
*/
@Native public final static int SO_TIMEOUT = 0x1006;
/**
* Set a hint the size of the underlying buffers used by the
* platform for outgoing network I/O. When used in set, this is a
* suggestion to the kernel from the application about the size of
* buffers to use for the data to be sent over the socket. When
* used in get, this must return the size of the buffer actually
* used by the platform when sending out data on this socket.
*
* Valid for all sockets: SocketImpl, DatagramSocketImpl
*
* @see Socket#setSendBufferSize
* @see Socket#getSendBufferSize
* @see DatagramSocket#setSendBufferSize
* @see DatagramSocket#getSendBufferSize
*/
@Native public final static int SO_SNDBUF = 0x1001;
/**
* Set a hint the size of the underlying buffers used by the
* platform for incoming network I/O. When used in set, this is a
* suggestion to the kernel from the application about the size of
* buffers to use for the data to be received over the
* socket. When used in get, this must return the size of the
* buffer actually used by the platform when receiving in data on
* this socket.
*
* Valid for all sockets: SocketImpl, DatagramSocketImpl
*
* @see Socket#setReceiveBufferSize
* @see Socket#getReceiveBufferSize
* @see DatagramSocket#setReceiveBufferSize
* @see DatagramSocket#getReceiveBufferSize
*/
@Native public final static int SO_RCVBUF = 0x1002;
/**
* When the keepalive option is set for a TCP socket and no data
* has been exchanged across the socket in either direction for
* 2 hours (NOTE: the actual value is implementation dependent),
* TCP automatically sends a keepalive probe to the peer. This probe is a
* TCP segment to which the peer must respond.
* One of three responses is expected:
* 1. The peer responds with the expected ACK. The application is not
* notified (since everything is OK). TCP will send another probe
* following another 2 hours of inactivity.
* 2. The peer responds with an RST, which tells the local TCP that
* the peer host has crashed and rebooted. The socket is closed.
* 3. There is no response from the peer. The socket is closed.
*
* The purpose of this option is to detect if the peer host crashes.
*
* Valid only for TCP socket: SocketImpl
*
* @see Socket#setKeepAlive
* @see Socket#getKeepAlive
*/
@Native public final static int SO_KEEPALIVE = 0x0008;
/**
* When the OOBINLINE option is set, any TCP urgent data received on
* the socket will be received through the socket input stream.
* When the option is disabled (which is the default) urgent data
* is silently discarded.
*
* @see Socket#setOOBInline
* @see Socket#getOOBInline
*/
@Native public final static int SO_OOBINLINE = 0x1003;
}
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