Java tutorial
/** * Copyright (C) 2013, Moss Computing Inc. * * This file is part of posix-fifo-sockets. * * posix-fifo-sockets is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2, or (at your option) * any later version. * * posix-fifo-sockets 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 for more details. * * You should have received a copy of the GNU General Public License * along with posix-fifo-sockets; see the file COPYING. If not, write to the * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA * 02110-1301 USA. * * Linking this library statically or dynamically with other modules is * making a combined work based on this library. Thus, the terms and * conditions of the GNU General Public License cover the whole * combination. * * As a special exception, the copyright holders of this library give you * permission to link this library with independent modules to produce an * executable, regardless of the license terms of these independent * modules, and to copy and distribute the resulting executable under * terms of your choice, provided that you also meet, for each linked * independent module, the terms and conditions of the license of that * module. An independent module is a module which is not derived from * or based on this library. If you modify this library, you may extend * this exception to your version of the library, but you are not * obligated to do so. If you do not wish to do so, delete this * exception statement from your version. */ package com.moss.posixfifosockets; import java.io.BufferedReader; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.FileReader; import java.io.FileWriter; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.OutputStream; import java.io.Reader; import java.io.Writer; import java.util.Random; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; public class PosixFifoSocket { private static final Random r = new Random(); public static PosixFifoSocket newClientConnection(PosixFifoSocketAddress address, int timeoutMillis) throws IOException { final Log log = LogFactory.getLog(PosixFifoSocket.class); if (!address.controlPipe().exists()) { throw new IOException("There is no server at " + address); } File in; File out; File control; long id; do { id = r.nextLong(); in = new File(address.socketsDir(), id + ".fifo.out"); out = new File(address.socketsDir(), id + ".fifo.in"); control = new File(address.socketsDir(), id + ".fifo.control"); } while (out.exists() || in.exists()); createFifo(in); createFifo(control); final String registrationString = "{" + id + "}"; if (log.isDebugEnabled()) log.debug("Sending registration " + registrationString); Writer w = new FileWriter(address.controlPipe()); w.write(registrationString); w.flush(); if (log.isDebugEnabled()) log.debug("Sent Registration " + registrationString); PosixFifoSocket socket = new PosixFifoSocket(id, in, out); Reader r = new FileReader(control); StringBuilder text = new StringBuilder(); for (int c = r.read(); c != -1 && c != '\n'; c = r.read()) { // READ UNTIL THE FIRST LINE BREAK text.append((char) c); } r.close(); if (!control.delete()) { throw new RuntimeException("Could not delete file:" + control.getAbsolutePath()); } if (!text.toString().equals("OK")) { throw new RuntimeException("Connection error: received \"" + text + "\""); } return socket; } private final File inFifo; private final File outFifo; private final long id; private InputStream in; private OutputStream out; public PosixFifoSocket(File l, long id, String input, String output) throws IOException { this(id, new File(l, id + input), new File(l, id + output)); } public long id() { return id; } public PosixFifoSocket(long name, File inFifo, File outFifo) throws IOException { super(); this.id = name; this.inFifo = inFifo; this.outFifo = outFifo; } public static void createFifo(File path) throws IOException { if (path.exists()) { throw new IOException("File already exists: " + path.getAbsolutePath()); } if (!path.getParentFile().exists()) { throw new FileNotFoundException(path.getParent()); } try { if (path.exists()) { throw new RuntimeException("Path really does exist: " + path.getAbsolutePath()); } final Process p = Runtime.getRuntime().exec("mkfifo " + path.getAbsolutePath()); int result = p.waitFor(); if (result != 0) { String stdOut = read(p.getInputStream()); String stdErr = read(p.getErrorStream()); throw new IOException("Error creating fifo at " + path.getAbsolutePath() + ": Received error code " + result + ", STDOUT: " + stdOut + ", STDERR: " + stdErr); } else if (!path.exists()) { throw new RuntimeException("mkfifo didn't do its job: " + path.getAbsolutePath()); } } catch (InterruptedException e) { throw new RuntimeException(e); } } private static String read(InputStream in) throws IOException { StringBuilder text = new StringBuilder(); char[] b = new char[1024]; BufferedReader r = new BufferedReader(new InputStreamReader(in)); for (int x = r.read(b); x != -1; x = r.read(b)) { text.append(b, 0, x); } r.close(); return text.toString(); } private boolean hasClosed = false; public void close() { if (hasClosed) { throw new RuntimeException("Socket already closed"); } if (!inFifo.delete()) { throw new RuntimeException("Could not delete one or both FIFOS: " + this); } hasClosed = true; } public synchronized InputStream in() throws IOException { if (in == null) { in = new FileInputStream(inFifo); } return in; } public synchronized OutputStream out() throws IOException { if (out == null) { out = new FileOutputStream(outFifo); } return out; } @Override public String toString() { return getClass().getSimpleName() + " # " + id + ", reading from " + inFifo + ", writing to " + outFifo; } }