/* * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package sun.nio.ch; import java.io.FileDescriptor; import java.io.IOException; import java.net.*; import java.nio.ByteBuffer; import java.nio.channels.*; import java.nio.channels.spi.*; import java.util.*; import sun.net.NetHooks; import sun.net.ExtendedOptionsImpl; /** * An implementation of SocketChannels */ class SocketChannelImpl extends SocketChannel implements SelChImpl { // Used to make native read and write calls private static NativeDispatcher nd; // Our file descriptor object private final FileDescriptor fd; // fd value needed for dev/poll. This value will remain valid // even after the value in the file descriptor object has been set to -1 private final int fdVal; // IDs of native threads doing reads and writes, for signalling private volatile long readerThread = 0; private volatile long writerThread = 0; // Lock held by current reading or connecting thread private final Object readLock = new Object(); // Lock held by current writing or connecting thread private final Object writeLock = new Object(); // Lock held by any thread that modifies the state fields declared below // DO NOT invoke a blocking I/O operation while holding this lock! private final Object stateLock = new Object(); // -- The following fields are protected by stateLock // set true when exclusive binding is on and SO_REUSEADDR is emulated private boolean isReuseAddress; // State, increases monotonically private static final int ST_UNINITIALIZED = -1; private static final int ST_UNCONNECTED = 0; private static final int ST_PENDING = 1; private static final int ST_CONNECTED = 2; private static final int ST_KILLPENDING = 3; private static final int ST_KILLED = 4; private int state = ST_UNINITIALIZED; // Binding private InetSocketAddress localAddress; private InetSocketAddress remoteAddress; // Input/Output open private boolean isInputOpen = true; private boolean isOutputOpen = true; private boolean readyToConnect = false; // Socket adaptor, created on demand private Socket socket; // -- End of fields protected by stateLock // Constructor for normal connecting sockets // SocketChannelImpl(SelectorProvider sp) throws IOException { super(sp); this.fd = Net.socket(true); this.fdVal = IOUtil.fdVal(fd); this.state = ST_UNCONNECTED; } SocketChannelImpl(SelectorProvider sp, FileDescriptor fd, boolean bound) throws IOException { super(sp); this.fd = fd; this.fdVal = IOUtil.fdVal(fd); this.state = ST_UNCONNECTED; if (bound) this.localAddress = Net.localAddress(fd); } // Constructor for sockets obtained from server sockets // SocketChannelImpl(SelectorProvider sp, FileDescriptor fd, InetSocketAddress remote) throws IOException { super(sp); this.fd = fd; this.fdVal = IOUtil.fdVal(fd); this.state = ST_CONNECTED; this.localAddress = Net.localAddress(fd); this.remoteAddress = remote; } public Socket socket() { synchronized (stateLock) { if (socket == null) socket = SocketAdaptor.create(this); return socket; } } @Override public SocketAddress getLocalAddress() throws IOException { synchronized (stateLock) { if (!isOpen()) throw new ClosedChannelException(); return Net.getRevealedLocalAddress(localAddress); } } @Override public SocketAddress getRemoteAddress() throws IOException { synchronized (stateLock) { if (!isOpen()) throw new ClosedChannelException(); return remoteAddress; } } @Override public SocketChannel setOption(SocketOption name, T value) throws IOException { if (name == null) throw new NullPointerException(); if (!supportedOptions().contains(name)) throw new UnsupportedOperationException("'" + name + "' not supported"); synchronized (stateLock) { if (!isOpen()) throw new ClosedChannelException(); if (name == StandardSocketOptions.IP_TOS) { ProtocolFamily family = Net.isIPv6Available() ? StandardProtocolFamily.INET6 : StandardProtocolFamily.INET; Net.setSocketOption(fd, family, name, value); return this; } if (name == StandardSocketOptions.SO_REUSEADDR && Net.useExclusiveBind()) { // SO_REUSEADDR emulated when using exclusive bind isReuseAddress = (Boolean)value; return this; } // no options that require special handling Net.setSocketOption(fd, Net.UNSPEC, name, value); return this; } } @Override @SuppressWarnings("unchecked") public T getOption(SocketOption name) throws IOException { if (name == null) throw new NullPointerException(); if (!supportedOptions().contains(name)) throw new UnsupportedOperationException("'" + name + "' not supported"); synchronized (stateLock) { if (!isOpen()) throw new ClosedChannelException(); if (name == StandardSocketOptions.SO_REUSEADDR && Net.useExclusiveBind()) { // SO_REUSEADDR emulated when using exclusive bind return (T)Boolean.valueOf(isReuseAddress); } // special handling for IP_TOS: always return 0 when IPv6 if (name == StandardSocketOptions.IP_TOS) { ProtocolFamily family = Net.isIPv6Available() ? StandardProtocolFamily.INET6 : StandardProtocolFamily.INET; return (T) Net.getSocketOption(fd, family, name); } // no options that require special handling return (T) Net.getSocketOption(fd, Net.UNSPEC, name); } } private static class DefaultOptionsHolder { static final Set> defaultOptions = defaultOptions(); private static Set> defaultOptions() { HashSet> set = new HashSet>(8); set.add(StandardSocketOptions.SO_SNDBUF); set.add(StandardSocketOptions.SO_RCVBUF); set.add(StandardSocketOptions.SO_KEEPALIVE); set.add(StandardSocketOptions.SO_REUSEADDR); set.add(StandardSocketOptions.SO_LINGER); set.add(StandardSocketOptions.TCP_NODELAY); // additional options required by socket adaptor set.add(StandardSocketOptions.IP_TOS); set.add(ExtendedSocketOption.SO_OOBINLINE); if (ExtendedOptionsImpl.flowSupported()) { set.add(jdk.net.ExtendedSocketOptions.SO_FLOW_SLA); } return Collections.unmodifiableSet(set); } } @Override public final Set> supportedOptions() { return DefaultOptionsHolder.defaultOptions; } private boolean ensureReadOpen() throws ClosedChannelException { synchronized (stateLock) { if (!isOpen()) throw new ClosedChannelException(); if (!isConnected()) throw new NotYetConnectedException(); if (!isInputOpen) return false; else return true; } } private void ensureWriteOpen() throws ClosedChannelException { synchronized (stateLock) { if (!isOpen()) throw new ClosedChannelException(); if (!isOutputOpen) throw new ClosedChannelException(); if (!isConnected()) throw new NotYetConnectedException(); } } private void readerCleanup() throws IOException { synchronized (stateLock) { readerThread = 0; if (state == ST_KILLPENDING) kill(); } } private void writerCleanup() throws IOException { synchronized (stateLock) { writerThread = 0; if (state == ST_KILLPENDING) kill(); } } public int read(ByteBuffer buf) throws IOException { if (buf == null) throw new NullPointerException(); synchronized (readLock) { if (!ensureReadOpen()) return -1; int n = 0; try { // Set up the interruption machinery; see // AbstractInterruptibleChannel for details // begin(); synchronized (stateLock) { if (!isOpen()) { // Either the current thread is already interrupted, so // begin() closed the channel, or another thread closed the // channel since we checked it a few bytecodes ago. In // either case the value returned here is irrelevant since // the invocation of end() in the finally block will throw // an appropriate exception. // return 0; } // Save this thread so that it can be signalled on those // platforms that require it // readerThread = NativeThread.current(); } // Between the previous test of isOpen() and the return of the // IOUtil.read invocation below, this channel might be closed // or this thread might be interrupted. We rely upon the // implicit synchronization point in the kernel read() call to // make sure that the right thing happens. In either case the // implCloseSelectableChannel method is ultimately invoked in // some other thread, so there are three possibilities: // // - implCloseSelectableChannel() invokes nd.preClose() // before this thread invokes read(), in which case the // read returns immediately with either EOF or an error, // the latter of which will cause an IOException to be // thrown. // // - implCloseSelectableChannel() invokes nd.preClose() after // this thread is blocked in read(). On some operating // systems (e.g., Solaris and Windows) this causes the read // to return immediately with either EOF or an error // indication. // // - implCloseSelectableChannel() invokes nd.preClose() after // this thread is blocked in read() but the operating // system (e.g., Linux) doesn't support preemptive close, // so implCloseSelectableChannel() proceeds to signal this // thread, thereby causing the read to return immediately // with IOStatus.INTERRUPTED. // // In all three cases the invocation of end() in the finally // clause will notice that the channel has been closed and // throw an appropriate exception (AsynchronousCloseException // or ClosedByInterruptException) if necessary. // // *There is A fourth possibility. implCloseSelectableChannel() // invokes nd.preClose(), signals reader/writer thred and quickly // moves on to nd.close() in kill(), which does a real close. // Then a third thread accepts a new connection, opens file or // whatever that causes the released "fd" to be recycled. All // above happens just between our last isOpen() check and the // next kernel read reached, with the recycled "fd". The solution // is to postpone the real kill() if there is a reader or/and // writer thread(s) over there "waiting", leave the cleanup/kill // to the reader or writer thread. (the preClose() still happens // so the connection gets cut off as usual). // // For socket channels there is the additional wrinkle that // asynchronous shutdown works much like asynchronous close, // except that the channel is shutdown rather than completely // closed. This is analogous to the first two cases above, // except that the shutdown operation plays the role of // nd.preClose(). for (;;) { n = IOUtil.read(fd, buf, -1, nd); if ((n == IOStatus.INTERRUPTED) && isOpen()) { // The system call was interrupted but the channel // is still open, so retry continue; } return IOStatus.normalize(n); } } finally { readerCleanup(); // Clear reader thread // The end method, which is defined in our superclass // AbstractInterruptibleChannel, resets the interruption // machinery. If its argument is true then it returns // normally; otherwise it checks the interrupt and open state // of this channel and throws an appropriate exception if // necessary. // // So, if we actually managed to do any I/O in the above try // block then we pass true to the end method. We also pass // true if the channel was in non-blocking mode when the I/O // operation was initiated but no data could be transferred; // this prevents spurious exceptions from being thrown in the // rare event that a channel is closed or a thread is // interrupted at the exact moment that a non-blocking I/O // request is made. // end(n > 0 || (n == IOStatus.UNAVAILABLE)); // Extra case for socket channels: Asynchronous shutdown // synchronized (stateLock) { if ((n <= 0) && (!isInputOpen)) return IOStatus.EOF; } assert IOStatus.check(n); } } } public long read(ByteBuffer[] dsts, int offset, int length) throws IOException { if ((offset < 0) || (length < 0) || (offset > dsts.length - length)) throw new IndexOutOfBoundsException(); synchronized (readLock) { if (!ensureReadOpen()) return -1; long n = 0; try { begin(); synchronized (stateLock) { if (!isOpen()) return 0; readerThread = NativeThread.current(); } for (;;) { n = IOUtil.read(fd, dsts, offset, length, nd); if ((n == IOStatus.INTERRUPTED) && isOpen()) continue; return IOStatus.normalize(n); } } finally { readerCleanup(); end(n > 0 || (n == IOStatus.UNAVAILABLE)); synchronized (stateLock) { if ((n <= 0) && (!isInputOpen)) return IOStatus.EOF; } assert IOStatus.check(n); } } } public int write(ByteBuffer buf) throws IOException { if (buf == null) throw new NullPointerException(); synchronized (writeLock) { ensureWriteOpen(); int n = 0; try { begin(); synchronized (stateLock) { if (!isOpen()) return 0; writerThread = NativeThread.current(); } for (;;) { n = IOUtil.write(fd, buf, -1, nd); if ((n == IOStatus.INTERRUPTED) && isOpen()) continue; return IOStatus.normalize(n); } } finally { writerCleanup(); end(n > 0 || (n == IOStatus.UNAVAILABLE)); synchronized (stateLock) { if ((n <= 0) && (!isOutputOpen)) throw new AsynchronousCloseException(); } assert IOStatus.check(n); } } } public long write(ByteBuffer[] srcs, int offset, int length) throws IOException { if ((offset < 0) || (length < 0) || (offset > srcs.length - length)) throw new IndexOutOfBoundsException(); synchronized (writeLock) { ensureWriteOpen(); long n = 0; try { begin(); synchronized (stateLock) { if (!isOpen()) return 0; writerThread = NativeThread.current(); } for (;;) { n = IOUtil.write(fd, srcs, offset, length, nd); if ((n == IOStatus.INTERRUPTED) && isOpen()) continue; return IOStatus.normalize(n); } } finally { writerCleanup(); end((n > 0) || (n == IOStatus.UNAVAILABLE)); synchronized (stateLock) { if ((n <= 0) && (!isOutputOpen)) throw new AsynchronousCloseException(); } assert IOStatus.check(n); } } } // package-private int sendOutOfBandData(byte b) throws IOException { synchronized (writeLock) { ensureWriteOpen(); int n = 0; try { begin(); synchronized (stateLock) { if (!isOpen()) return 0; writerThread = NativeThread.current(); } for (;;) { n = sendOutOfBandData(fd, b); if ((n == IOStatus.INTERRUPTED) && isOpen()) continue; return IOStatus.normalize(n); } } finally { writerCleanup(); end((n > 0) || (n == IOStatus.UNAVAILABLE)); synchronized (stateLock) { if ((n <= 0) && (!isOutputOpen)) throw new AsynchronousCloseException(); } assert IOStatus.check(n); } } } protected void implConfigureBlocking(boolean block) throws IOException { IOUtil.configureBlocking(fd, block); } public InetSocketAddress localAddress() { synchronized (stateLock) { return localAddress; } } public SocketAddress remoteAddress() { synchronized (stateLock) { return remoteAddress; } } @Override public SocketChannel bind(SocketAddress local) throws IOException { synchronized (readLock) { synchronized (writeLock) { synchronized (stateLock) { if (!isOpen()) throw new ClosedChannelException(); if (state == ST_PENDING) throw new ConnectionPendingException(); if (localAddress != null) throw new AlreadyBoundException(); InetSocketAddress isa = (local == null) ? new InetSocketAddress(0) : Net.checkAddress(local); SecurityManager sm = System.getSecurityManager(); if (sm != null) { sm.checkListen(isa.getPort()); } NetHooks.beforeTcpBind(fd, isa.getAddress(), isa.getPort()); Net.bind(fd, isa.getAddress(), isa.getPort()); localAddress = Net.localAddress(fd); } } } return this; } public boolean isConnected() { synchronized (stateLock) { return (state == ST_CONNECTED); } } public boolean isConnectionPending() { synchronized (stateLock) { return (state == ST_PENDING); } } void ensureOpenAndUnconnected() throws IOException { // package-private synchronized (stateLock) { if (!isOpen()) throw new ClosedChannelException(); if (state == ST_CONNECTED) throw new AlreadyConnectedException(); if (state == ST_PENDING) throw new ConnectionPendingException(); } } public boolean connect(SocketAddress sa) throws IOException { int localPort = 0; synchronized (readLock) { synchronized (writeLock) { ensureOpenAndUnconnected(); InetSocketAddress isa = Net.checkAddress(sa); SecurityManager sm = System.getSecurityManager(); if (sm != null) sm.checkConnect(isa.getAddress().getHostAddress(), isa.getPort()); synchronized (blockingLock()) { int n = 0; try { try { begin(); synchronized (stateLock) { if (!isOpen()) { return false; } // notify hook only if unbound if (localAddress == null) { NetHooks.beforeTcpConnect(fd, isa.getAddress(), isa.getPort()); } readerThread = NativeThread.current(); } for (;;) { InetAddress ia = isa.getAddress(); if (ia.isAnyLocalAddress()) ia = InetAddress.getLocalHost(); n = Net.connect(fd, ia, isa.getPort()); if ( (n == IOStatus.INTERRUPTED) && isOpen()) continue; break; } } finally { readerCleanup(); end((n > 0) || (n == IOStatus.UNAVAILABLE)); assert IOStatus.check(n); } } catch (IOException x) { // If an exception was thrown, close the channel after // invoking end() so as to avoid bogus // AsynchronousCloseExceptions close(); throw x; } synchronized (stateLock) { remoteAddress = isa; if (n > 0) { // Connection succeeded; disallow further // invocation state = ST_CONNECTED; if (isOpen()) localAddress = Net.localAddress(fd); return true; } // If nonblocking and no exception then connection // pending; disallow another invocation if (!isBlocking()) state = ST_PENDING; else assert false; } } return false; } } } public boolean finishConnect() throws IOException { synchronized (readLock) { synchronized (writeLock) { synchronized (stateLock) { if (!isOpen()) throw new ClosedChannelException(); if (state == ST_CONNECTED) return true; if (state != ST_PENDING) throw new NoConnectionPendingException(); } int n = 0; try { try { begin(); synchronized (blockingLock()) { synchronized (stateLock) { if (!isOpen()) { return false; } readerThread = NativeThread.current(); } if (!isBlocking()) { for (;;) { n = checkConnect(fd, false, readyToConnect); if ( (n == IOStatus.INTERRUPTED) && isOpen()) continue; break; } } else { for (;;) { n = checkConnect(fd, true, readyToConnect); if (n == 0) { // Loop in case of // spurious notifications continue; } if ( (n == IOStatus.INTERRUPTED) && isOpen()) continue; break; } } } } finally { synchronized (stateLock) { readerThread = 0; if (state == ST_KILLPENDING) { kill(); // poll()/getsockopt() does not report // error (throws exception, with n = 0) // on Linux platform after dup2 and // signal-wakeup. Force n to 0 so the // end() can throw appropriate exception n = 0; } } end((n > 0) || (n == IOStatus.UNAVAILABLE)); assert IOStatus.check(n); } } catch (IOException x) { // If an exception was thrown, close the channel after // invoking end() so as to avoid bogus // AsynchronousCloseExceptions close(); throw x; } if (n > 0) { synchronized (stateLock) { state = ST_CONNECTED; if (isOpen()) localAddress = Net.localAddress(fd); } return true; } return false; } } } @Override public SocketChannel shutdownInput() throws IOException { synchronized (stateLock) { if (!isOpen()) throw new ClosedChannelException(); if (!isConnected()) throw new NotYetConnectedException(); if (isInputOpen) { Net.shutdown(fd, Net.SHUT_RD); if (readerThread != 0) NativeThread.signal(readerThread); isInputOpen = false; } return this; } } @Override public SocketChannel shutdownOutput() throws IOException { synchronized (stateLock) { if (!isOpen()) throw new ClosedChannelException(); if (!isConnected()) throw new NotYetConnectedException(); if (isOutputOpen) { Net.shutdown(fd, Net.SHUT_WR); if (writerThread != 0) NativeThread.signal(writerThread); isOutputOpen = false; } return this; } } public boolean isInputOpen() { synchronized (stateLock) { return isInputOpen; } } public boolean isOutputOpen() { synchronized (stateLock) { return isOutputOpen; } } // AbstractInterruptibleChannel synchronizes invocations of this method // using AbstractInterruptibleChannel.closeLock, and also ensures that this // method is only ever invoked once. Before we get to this method, isOpen // (which is volatile) will have been set to false. // protected void implCloseSelectableChannel() throws IOException { synchronized (stateLock) { isInputOpen = false; isOutputOpen = false; // Close the underlying file descriptor and dup it to a known fd // that's already closed. This prevents other operations on this // channel from using the old fd, which might be recycled in the // meantime and allocated to an entirely different channel. // if (state != ST_KILLED) nd.preClose(fd); // Signal native threads, if needed. If a target thread is not // currently blocked in an I/O operation then no harm is done since // the signal handler doesn't actually do anything. // if (readerThread != 0) NativeThread.signal(readerThread); if (writerThread != 0) NativeThread.signal(writerThread); // If this channel is not registered then it's safe to close the fd // immediately since we know at this point that no thread is // blocked in an I/O operation upon the channel and, since the // channel is marked closed, no thread will start another such // operation. If this channel is registered then we don't close // the fd since it might be in use by a selector. In that case // closing this channel caused its keys to be cancelled, so the // last selector to deregister a key for this channel will invoke // kill() to close the fd. // if (!isRegistered()) kill(); } } public void kill() throws IOException { synchronized (stateLock) { if (state == ST_KILLED) return; if (state == ST_UNINITIALIZED) { state = ST_KILLED; return; } assert !isOpen() && !isRegistered(); // Postpone the kill if there is a waiting reader // or writer thread. See the comments in read() for // more detailed explanation. if (readerThread == 0 && writerThread == 0) { nd.close(fd); state = ST_KILLED; } else { state = ST_KILLPENDING; } } } /** * Translates native poll revent ops into a ready operation ops */ public boolean translateReadyOps(int ops, int initialOps, SelectionKeyImpl sk) { int intOps = sk.nioInterestOps(); // Do this just once, it synchronizes int oldOps = sk.nioReadyOps(); int newOps = initialOps; if ((ops & Net.POLLNVAL) != 0) { // This should only happen if this channel is pre-closed while a // selection operation is in progress // ## Throw an error if this channel has not been pre-closed return false; } if ((ops & (Net.POLLERR | Net.POLLHUP)) != 0) { newOps = intOps; sk.nioReadyOps(newOps); // No need to poll again in checkConnect, // the error will be detected there readyToConnect = true; return (newOps & ~oldOps) != 0; } if (((ops & Net.POLLIN) != 0) && ((intOps & SelectionKey.OP_READ) != 0) && (state == ST_CONNECTED)) newOps |= SelectionKey.OP_READ; if (((ops & Net.POLLCONN) != 0) && ((intOps & SelectionKey.OP_CONNECT) != 0) && ((state == ST_UNCONNECTED) || (state == ST_PENDING))) { newOps |= SelectionKey.OP_CONNECT; readyToConnect = true; } if (((ops & Net.POLLOUT) != 0) && ((intOps & SelectionKey.OP_WRITE) != 0) && (state == ST_CONNECTED)) newOps |= SelectionKey.OP_WRITE; sk.nioReadyOps(newOps); return (newOps & ~oldOps) != 0; } public boolean translateAndUpdateReadyOps(int ops, SelectionKeyImpl sk) { return translateReadyOps(ops, sk.nioReadyOps(), sk); } public boolean translateAndSetReadyOps(int ops, SelectionKeyImpl sk) { return translateReadyOps(ops, 0, sk); } // package-private int poll(int events, long timeout) throws IOException { assert Thread.holdsLock(blockingLock()) && !isBlocking(); synchronized (readLock) { int n = 0; try { begin(); synchronized (stateLock) { if (!isOpen()) return 0; readerThread = NativeThread.current(); } n = Net.poll(fd, events, timeout); } finally { readerCleanup(); end(n > 0); } return n; } } /** * Translates an interest operation set into a native poll event set */ public void translateAndSetInterestOps(int ops, SelectionKeyImpl sk) { int newOps = 0; if ((ops & SelectionKey.OP_READ) != 0) newOps |= Net.POLLIN; if ((ops & SelectionKey.OP_WRITE) != 0) newOps |= Net.POLLOUT; if ((ops & SelectionKey.OP_CONNECT) != 0) newOps |= Net.POLLCONN; sk.selector.putEventOps(sk, newOps); } public FileDescriptor getFD() { return fd; } public int getFDVal() { return fdVal; } @Override public String toString() { StringBuffer sb = new StringBuffer(); sb.append(this.getClass().getSuperclass().getName()); sb.append('['); if (!isOpen()) sb.append("closed"); else { synchronized (stateLock) { switch (state) { case ST_UNCONNECTED: sb.append("unconnected"); break; case ST_PENDING: sb.append("connection-pending"); break; case ST_CONNECTED: sb.append("connected"); if (!isInputOpen) sb.append(" ishut"); if (!isOutputOpen) sb.append(" oshut"); break; } InetSocketAddress addr = localAddress(); if (addr != null) { sb.append(" local="); sb.append(Net.getRevealedLocalAddressAsString(addr)); } if (remoteAddress() != null) { sb.append(" remote="); sb.append(remoteAddress().toString()); } } } sb.append(']'); return sb.toString(); } // -- Native methods -- private static native int checkConnect(FileDescriptor fd, boolean block, boolean ready) throws IOException; private static native int sendOutOfBandData(FileDescriptor fd, byte data) throws IOException; static { IOUtil.load(); nd = new SocketDispatcher(); } }