1 /* 2 * Copyright (c) 1996, 2006, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.net; 27 28 /** 29 * Interface of methods to get/set socket options. This interface is 30 * implemented by: <B>SocketImpl</B> and <B>DatagramSocketImpl</B>. 31 * Subclasses of these should override the methods 32 * of this interface in order to support their own options. 33 * <P> 34 * The methods and constants which specify options in this interface are 35 * for implementation only. If you're not subclassing SocketImpl or 36 * DatagramSocketImpl, <B>you won't use these directly.</B> There are 37 * type-safe methods to get/set each of these options in Socket, ServerSocket, 38 * DatagramSocket and MulticastSocket. 39 * <P> 40 * @author David Brown 41 */ 42 43 44 public interface SocketOptions { 45 46 /** 47 * Enable/disable the option specified by <I>optID</I>. If the option 48 * is to be enabled, and it takes an option-specific "value", this is 49 * passed in <I>value</I>. The actual type of value is option-specific, 50 * and it is an error to pass something that isn't of the expected type: 51 * <BR><PRE> 52 * SocketImpl s; 53 * ... 54 * s.setOption(SO_LINGER, new Integer(10)); 55 * // OK - set SO_LINGER w/ timeout of 10 sec. 56 * s.setOption(SO_LINGER, new Double(10)); 57 * // ERROR - expects java.lang.Integer 58 *</PRE> 59 * If the requested option is binary, it can be set using this method by 60 * a java.lang.Boolean: 61 * <BR><PRE> 62 * s.setOption(TCP_NODELAY, new Boolean(true)); 63 * // OK - enables TCP_NODELAY, a binary option 64 * </PRE> 65 * <BR> 66 * Any option can be disabled using this method with a Boolean(false): 67 * <BR><PRE> 68 * s.setOption(TCP_NODELAY, new Boolean(false)); 69 * // OK - disables TCP_NODELAY 70 * s.setOption(SO_LINGER, new Boolean(false)); 71 * // OK - disables SO_LINGER 72 * </PRE> 73 * <BR> 74 * For an option that has a notion of on and off, and requires 75 * a non-boolean parameter, setting its value to anything other than 76 * <I>Boolean(false)</I> implicitly enables it. 77 * <BR> 78 * Throws SocketException if the option is unrecognized, 79 * the socket is closed, or some low-level error occurred 80 * <BR> 81 * @param optID identifies the option 82 * @param value the parameter of the socket option 83 * @throws SocketException if the option is unrecognized, 84 * the socket is closed, or some low-level error occurred 85 * @see #getOption(int) 86 */ 87 public void setOption(int optID, Object value)88 setOption(int optID, Object value) throws SocketException; 89 90 /** 91 * Fetch the value of an option. 92 * Binary options will return java.lang.Boolean(true) 93 * if enabled, java.lang.Boolean(false) if disabled, e.g.: 94 * <BR><PRE> 95 * SocketImpl s; 96 * ... 97 * Boolean noDelay = (Boolean)(s.getOption(TCP_NODELAY)); 98 * if (noDelay.booleanValue()) { 99 * // true if TCP_NODELAY is enabled... 100 * ... 101 * } 102 * </PRE> 103 * <P> 104 * For options that take a particular type as a parameter, 105 * getOption(int) will return the parameter's value, else 106 * it will return java.lang.Boolean(false): 107 * <PRE> 108 * Object o = s.getOption(SO_LINGER); 109 * if (o instanceof Integer) { 110 * System.out.print("Linger time is " + ((Integer)o).intValue()); 111 * } else { 112 * // the true type of o is java.lang.Boolean(false); 113 * } 114 * </PRE> 115 * 116 * @param optID an <code>int</code> identifying the option to fetch 117 * @return the value of the option 118 * @throws SocketException if the socket is closed 119 * @throws SocketException if <I>optID</I> is unknown along the 120 * protocol stack (including the SocketImpl) 121 * @see #setOption(int, java.lang.Object) 122 */ getOption(int optID)123 public Object getOption(int optID) throws SocketException; 124 125 /** 126 * The java-supported BSD-style options. 127 */ 128 129 /** 130 * Disable Nagle's algorithm for this connection. Written data 131 * to the network is not buffered pending acknowledgement of 132 * previously written data. 133 *<P> 134 * Valid for TCP only: SocketImpl. 135 * <P> 136 * @see Socket#setTcpNoDelay 137 * @see Socket#getTcpNoDelay 138 */ 139 140 public final static int TCP_NODELAY = 0x0001; 141 142 /** 143 * Fetch the local address binding of a socket (this option cannot 144 * be "set" only "gotten", since sockets are bound at creation time, 145 * and so the locally bound address cannot be changed). The default local 146 * address of a socket is INADDR_ANY, meaning any local address on a 147 * multi-homed host. A multi-homed host can use this option to accept 148 * connections to only one of its addresses (in the case of a 149 * ServerSocket or DatagramSocket), or to specify its return address 150 * to the peer (for a Socket or DatagramSocket). The parameter of 151 * this option is an InetAddress. 152 * <P> 153 * This option <B>must</B> be specified in the constructor. 154 * <P> 155 * Valid for: SocketImpl, DatagramSocketImpl 156 * <P> 157 * @see Socket#getLocalAddress 158 * @see DatagramSocket#getLocalAddress 159 */ 160 161 public final static int SO_BINDADDR = 0x000F; 162 163 /** Sets SO_REUSEADDR for a socket. This is used only for MulticastSockets 164 * in java, and it is set by default for MulticastSockets. 165 * <P> 166 * Valid for: DatagramSocketImpl 167 */ 168 169 public final static int SO_REUSEADDR = 0x04; 170 171 /** 172 * Sets SO_BROADCAST for a socket. This option enables and disables 173 * the ability of the process to send broadcast messages. It is supported 174 * for only datagram sockets and only on networks that support 175 * the concept of a broadcast message (e.g. Ethernet, token ring, etc.), 176 * and it is set by default for DatagramSockets. 177 * @since 1.4 178 */ 179 180 public final static int SO_BROADCAST = 0x0020; 181 182 /** Set which outgoing interface on which to send multicast packets. 183 * Useful on hosts with multiple network interfaces, where applications 184 * want to use other than the system default. Takes/returns an InetAddress. 185 * <P> 186 * Valid for Multicast: DatagramSocketImpl 187 * <P> 188 * @see MulticastSocket#setInterface(InetAddress) 189 * @see MulticastSocket#getInterface() 190 */ 191 192 public final static int IP_MULTICAST_IF = 0x10; 193 194 /** Same as above. This option is introduced so that the behaviour 195 * with IP_MULTICAST_IF will be kept the same as before, while 196 * this new option can support setting outgoing interfaces with either 197 * IPv4 and IPv6 addresses. 198 * 199 * NOTE: make sure there is no conflict with this 200 * @see MulticastSocket#setNetworkInterface(NetworkInterface) 201 * @see MulticastSocket#getNetworkInterface() 202 * @since 1.4 203 */ 204 public final static int IP_MULTICAST_IF2 = 0x1f; 205 206 /** 207 * This option enables or disables local loopback of multicast datagrams. 208 * This option is enabled by default for Multicast Sockets. 209 * @since 1.4 210 */ 211 212 public final static int IP_MULTICAST_LOOP = 0x12; 213 214 /** 215 * This option sets the type-of-service or traffic class field 216 * in the IP header for a TCP or UDP socket. 217 * @since 1.4 218 */ 219 220 public final static int IP_TOS = 0x3; 221 222 /** 223 * Specify a linger-on-close timeout. This option disables/enables 224 * immediate return from a <B>close()</B> of a TCP Socket. Enabling 225 * this option with a non-zero Integer <I>timeout</I> means that a 226 * <B>close()</B> will block pending the transmission and acknowledgement 227 * of all data written to the peer, at which point the socket is closed 228 * <I>gracefully</I>. Upon reaching the linger timeout, the socket is 229 * closed <I>forcefully</I>, with a TCP RST. Enabling the option with a 230 * timeout of zero does a forceful close immediately. If the specified 231 * timeout value exceeds 65,535 it will be reduced to 65,535. 232 * <P> 233 * Valid only for TCP: SocketImpl 234 * 235 * @see Socket#setSoLinger 236 * @see Socket#getSoLinger 237 */ 238 public final static int SO_LINGER = 0x0080; 239 240 /** Set a timeout on blocking Socket operations: 241 * <PRE> 242 * ServerSocket.accept(); 243 * SocketInputStream.read(); 244 * DatagramSocket.receive(); 245 * </PRE> 246 * 247 * <P> The option must be set prior to entering a blocking 248 * operation to take effect. If the timeout expires and the 249 * operation would continue to block, 250 * <B>java.io.InterruptedIOException</B> is raised. The Socket is 251 * not closed in this case. 252 * 253 * <P> Valid for all sockets: SocketImpl, DatagramSocketImpl 254 * 255 * @see Socket#setSoTimeout 256 * @see ServerSocket#setSoTimeout 257 * @see DatagramSocket#setSoTimeout 258 */ 259 public final static int SO_TIMEOUT = 0x1006; 260 261 /** 262 * Set a hint the size of the underlying buffers used by the 263 * platform for outgoing network I/O. When used in set, this is a 264 * suggestion to the kernel from the application about the size of 265 * buffers to use for the data to be sent over the socket. When 266 * used in get, this must return the size of the buffer actually 267 * used by the platform when sending out data on this socket. 268 * 269 * Valid for all sockets: SocketImpl, DatagramSocketImpl 270 * 271 * @see Socket#setSendBufferSize 272 * @see Socket#getSendBufferSize 273 * @see DatagramSocket#setSendBufferSize 274 * @see DatagramSocket#getSendBufferSize 275 */ 276 public final static int SO_SNDBUF = 0x1001; 277 278 /** 279 * Set a hint the size of the underlying buffers used by the 280 * platform for incoming network I/O. When used in set, this is a 281 * suggestion to the kernel from the application about the size of 282 * buffers to use for the data to be received over the 283 * socket. When used in get, this must return the size of the 284 * buffer actually used by the platform when receiving in data on 285 * this socket. 286 * 287 * Valid for all sockets: SocketImpl, DatagramSocketImpl 288 * 289 * @see Socket#setReceiveBufferSize 290 * @see Socket#getReceiveBufferSize 291 * @see DatagramSocket#setReceiveBufferSize 292 * @see DatagramSocket#getReceiveBufferSize 293 */ 294 public final static int SO_RCVBUF = 0x1002; 295 296 /** 297 * When the keepalive option is set for a TCP socket and no data 298 * has been exchanged across the socket in either direction for 299 * 2 hours (NOTE: the actual value is implementation dependent), 300 * TCP automatically sends a keepalive probe to the peer. This probe is a 301 * TCP segment to which the peer must respond. 302 * One of three responses is expected: 303 * 1. The peer responds with the expected ACK. The application is not 304 * notified (since everything is OK). TCP will send another probe 305 * following another 2 hours of inactivity. 306 * 2. The peer responds with an RST, which tells the local TCP that 307 * the peer host has crashed and rebooted. The socket is closed. 308 * 3. There is no response from the peer. The socket is closed. 309 * 310 * The purpose of this option is to detect if the peer host crashes. 311 * 312 * Valid only for TCP socket: SocketImpl 313 * 314 * @see Socket#setKeepAlive 315 * @see Socket#getKeepAlive 316 */ 317 public final static int SO_KEEPALIVE = 0x0008; 318 319 /** 320 * When the OOBINLINE option is set, any TCP urgent data received on 321 * the socket will be received through the socket input stream. 322 * When the option is disabled (which is the default) urgent data 323 * is silently discarded. 324 * 325 * @see Socket#setOOBInline 326 * @see Socket#getOOBInline 327 */ 328 public final static int SO_OOBINLINE = 0x1003; 329 } 330