* The methods and constants which specify options in this interface are * for implementation only. If you're not subclassing SocketImpl or * DatagramSocketImpl, you won't use these directly. There are * type-safe methods to get/set each of these options in Socket, ServerSocket, * DatagramSocket and MulticastSocket. *
* @author David Brown
*/
public interface SocketOptions {
/**
* Enable/disable the option specified by optID. If the option
* is to be enabled, and it takes an option-specific "value", this is
* passed in value. The actual type of value is option-specific,
* and it is an error to pass something that isn't of the expected type:
*
* 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
*
* If the requested option is binary, it can be set using this method by
* a java.lang.Boolean:
*
* s.setOption(TCP_NODELAY, new Boolean(true));
* // OK - enables TCP_NODELAY, a binary option
*
*
* s.setOption(TCP_NODELAY, new Boolean(false));
* // OK - disables TCP_NODELAY
* s.setOption(SO_LINGER, new Boolean(false));
* // OK - disables SO_LINGER
*
*
* SocketImpl s;
* ...
* Boolean noDelay = (Boolean)(s.getOption(TCP_NODELAY));
* if (noDelay.booleanValue()) {
* // true if TCP_NODELAY is enabled...
* ...
* }
*
* * 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): *
* 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);
* }
*
*
* @param optID an int identifying the option to fetch
* @return the value of the option
* @throws SocketException if the socket is closed
* @throws SocketException if 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.
** Valid for TCP only: SocketImpl. *
* @see Socket#setTcpNoDelay * @see Socket#getTcpNoDelay */ 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. *
* This option must be specified in the constructor. *
* Valid for: SocketImpl, DatagramSocketImpl *
* @see Socket#getLocalAddress * @see DatagramSocket#getLocalAddress */ 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. *
* Valid for: DatagramSocketImpl */ 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 */ 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. *
* Valid for Multicast: DatagramSocketImpl *
* @see MulticastSocket#setInterface(InetAddress) * @see MulticastSocket#getInterface() */ 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 */ 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 */ 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 */ public final static int IP_TOS = 0x3; /** * Specify a linger-on-close timeout. This option disables/enables * immediate return from a close() of a TCP Socket. Enabling * this option with a non-zero Integer timeout means that a * close() will block pending the transmission and acknowledgement * of all data written to the peer, at which point the socket is closed * gracefully. Upon reaching the linger timeout, the socket is * closed 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. *
* Valid only for TCP: SocketImpl * * @see Socket#setSoLinger * @see Socket#getSoLinger */ public final static int SO_LINGER = 0x0080; /** Set a timeout on blocking Socket operations: *
* ServerSocket.accept();
* SocketInputStream.read();
* DatagramSocket.receive();
*
*
* 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, * java.io.InterruptedIOException is raised. The Socket is * not closed in this case. * *
Valid for all sockets: SocketImpl, DatagramSocketImpl * * @see Socket#setSoTimeout * @see ServerSocket#setSoTimeout * @see DatagramSocket#setSoTimeout */ 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 */ 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 */ 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 */ 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 */ public final static int SO_OOBINLINE = 0x1003; }