flink-core/src/main/java/org/apache/flink/util/NetUtils.java - flink - Git at Google

 /*
  * Licensed to the Apache Software Foundation (ASF) under one
  * or more contributor license agreements.  See the NOTICE file
  * distributed with this work for additional information
  * regarding copyright ownership.  The ASF licenses this file
  * to you under the Apache License, Version 2.0 (the
  * "License"); you may not use this file except in compliance
  * with the License.  You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 package org.apache.flink.util;

 import org.apache.flink.annotation.Internal;
 import org.apache.flink.configuration.IllegalConfigurationException;

 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import sun.net.util.IPAddressUtil;

 import java.io.IOException;
 import java.net.Inet4Address;
 import java.net.Inet6Address;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.MalformedURLException;
 import java.net.ServerSocket;
 import java.net.URL;
 import java.net.UnknownHostException;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.Iterator;

 /** Utility for various network related tasks (such as finding free ports). */
 @Internal
 public class NetUtils {

     private static final Logger LOG = LoggerFactory.getLogger(NetUtils.class);

     /** The wildcard address to listen on all interfaces (either 0.0.0.0 or ::). */
     private static final String WILDCARD_ADDRESS =
             new InetSocketAddress(0).getAddress().getHostAddress();

     /**
      * Turn a fully qualified domain name (fqdn) into a hostname. If the fqdn has multiple subparts
      * (separated by a period '.'), it will take the first part. Otherwise it takes the entire fqdn.
      *
      * @param fqdn The fully qualified domain name.
      * @return The hostname.
      */
     public static String getHostnameFromFQDN(String fqdn) {
         if (fqdn == null) {
             throw new IllegalArgumentException("fqdn is null");
         }
         int dotPos = fqdn.indexOf('.');
         if (dotPos == -1) {
             return fqdn;
         } else {
             return fqdn.substring(0, dotPos);
         }
     }

     /**
      * Converts a string of the form "host:port" into an {@link URL}.
      *
      * @param hostPort The "host:port" string.
      * @return The converted URL.
      */
     public static URL getCorrectHostnamePort(String hostPort) {
         return validateHostPortString(hostPort);
     }

     /**
      * Converts a string of the form "host:port" into an {@link InetSocketAddress}.
      *
      * @param hostPort The "host:port" string.
      * @return The converted InetSocketAddress.
      */
     public static InetSocketAddress parseHostPortAddress(String hostPort) {
         URL url = validateHostPortString(hostPort);
         return new InetSocketAddress(url.getHost(), url.getPort());
     }

     /**
      * Validates if the given String represents a hostname:port.
      *
      * <p>Works also for ipv6.
      *
      * <p>See:
      * http://stackoverflow.com/questions/2345063/java-common-way-to-validate-and-convert-hostport-to-inetsocketaddress
      *
      * @return URL object for accessing host and port
      */
     private static URL validateHostPortString(String hostPort) {
         try {
             URL u = new URL("http://" + hostPort);
             if (u.getHost() == null) {
                 throw new IllegalArgumentException(
                         "The given host:port ('" + hostPort + "') doesn't contain a valid host");
             }
             if (u.getPort() == -1) {
                 throw new IllegalArgumentException(
                         "The given host:port ('" + hostPort + "') doesn't contain a valid port");
             }
             return u;
         } catch (MalformedURLException e) {
             throw new IllegalArgumentException(
                     "The given host:port ('" + hostPort + "') is invalid", e);
         }
     }

     // ------------------------------------------------------------------------
     //  Lookup of to free ports
     // ------------------------------------------------------------------------

     /**
      * Find a non-occupied port.
      *
      * @return A non-occupied port.
      */
     public static int getAvailablePort() {
         for (int i = 0; i < 50; i++) {
             try (ServerSocket serverSocket = new ServerSocket(0)) {
                 int port = serverSocket.getLocalPort();
                 if (port != 0) {
                     return port;
                 }
             } catch (IOException ignored) {
             }
         }

         throw new RuntimeException("Could not find a free permitted port on the machine.");
     }

     // ------------------------------------------------------------------------
     //  Encoding of IP addresses for URLs
     // ------------------------------------------------------------------------

     /**
      * Returns an address in a normalized format for Akka. When an IPv6 address is specified, it
      * normalizes the IPv6 address to avoid complications with the exact URL match policy of Akka.
      *
      * @param host The hostname, IPv4 or IPv6 address
      * @return host which will be normalized if it is an IPv6 address
      */
     public static String unresolvedHostToNormalizedString(String host) {
         // Return loopback interface address if host is null
         // This represents the behavior of {@code InetAddress.getByName } and RFC 3330
         if (host == null) {
             host = InetAddress.getLoopbackAddress().getHostAddress();
         } else {
             host = host.trim().toLowerCase();
             if (host.startsWith("[") && host.endsWith("]")) {
                 String address = host.substring(1, host.length() - 1);
                 if (IPAddressUtil.isIPv6LiteralAddress(address)) {
                     host = address;
                 }
             }
         }

         // normalize and valid address
         if (IPAddressUtil.isIPv6LiteralAddress(host)) {
             byte[] ipV6Address = IPAddressUtil.textToNumericFormatV6(host);
             host = getIPv6UrlRepresentation(ipV6Address);
         } else if (!IPAddressUtil.isIPv4LiteralAddress(host)) {
             try {
                 // We don't allow these in hostnames
                 Preconditions.checkArgument(!host.startsWith("."));
                 Preconditions.checkArgument(!host.endsWith("."));
                 Preconditions.checkArgument(!host.contains(":"));
             } catch (Exception e) {
                 throw new IllegalConfigurationException("The configured hostname is not valid", e);
             }
         }

         return host;
     }

     /**
      * Returns a valid address for Akka. It returns a String of format 'host:port'. When an IPv6
      * address is specified, it normalizes the IPv6 address to avoid complications with the exact
      * URL match policy of Akka.
      *
      * @param host The hostname, IPv4 or IPv6 address
      * @param port The port
      * @return host:port where host will be normalized if it is an IPv6 address
      */
     public static String unresolvedHostAndPortToNormalizedString(String host, int port) {
         Preconditions.checkArgument(isValidHostPort(port), "Port is not within the valid range,");
         return unresolvedHostToNormalizedString(host) + ":" + port;
     }

     /**
      * Encodes an IP address properly as a URL string. This method makes sure that IPv6 addresses
      * have the proper formatting to be included in URLs.
      *
      * @param address The IP address to encode.
      * @return The proper URL string encoded IP address.
      */
     public static String ipAddressToUrlString(InetAddress address) {
         if (address == null) {
             throw new NullPointerException("address is null");
         } else if (address instanceof Inet4Address) {
             return address.getHostAddress();
         } else if (address instanceof Inet6Address) {
             return getIPv6UrlRepresentation((Inet6Address) address);
         } else {
             throw new IllegalArgumentException("Unrecognized type of InetAddress: " + address);
         }
     }

     /**
      * Encodes an IP address and port to be included in URL. in particular, this method makes sure
      * that IPv6 addresses have the proper formatting to be included in URLs.
      *
      * @param address The address to be included in the URL.
      * @param port The port for the URL address.
      * @return The proper URL string encoded IP address and port.
      */
     public static String ipAddressAndPortToUrlString(InetAddress address, int port) {
         return ipAddressToUrlString(address) + ':' + port;
     }

     /**
      * Encodes an IP address and port to be included in URL. in particular, this method makes sure
      * that IPv6 addresses have the proper formatting to be included in URLs.
      *
      * @param address The socket address with the IP address and port.
      * @return The proper URL string encoded IP address and port.
      */
     public static String socketAddressToUrlString(InetSocketAddress address) {
         if (address.isUnresolved()) {
             throw new IllegalArgumentException(
                     "Address cannot be resolved: " + address.getHostString());
         }
         return ipAddressAndPortToUrlString(address.getAddress(), address.getPort());
     }

     /**
      * Normalizes and encodes a hostname and port to be included in URL. In particular, this method
      * makes sure that IPv6 address literals have the proper formatting to be included in URLs.
      *
      * @param host The address to be included in the URL.
      * @param port The port for the URL address.
      * @return The proper URL string encoded IP address and port.
      * @throws java.net.UnknownHostException Thrown, if the hostname cannot be translated into a
      *     URL.
      */
     public static String hostAndPortToUrlString(String host, int port) throws UnknownHostException {
         return ipAddressAndPortToUrlString(InetAddress.getByName(host), port);
     }

     /**
      * Creates a compressed URL style representation of an Inet6Address.
      *
      * <p>This method copies and adopts code from Google's Guava library. We re-implement this here
      * in order to reduce dependency on Guava. The Guava library has frequently caused dependency
      * conflicts in the past.
      */
     private static String getIPv6UrlRepresentation(Inet6Address address) {
         return getIPv6UrlRepresentation(address.getAddress());
     }

     /**
      * Creates a compressed URL style representation of an Inet6Address.
      *
      * <p>This method copies and adopts code from Google's Guava library. We re-implement this here
      * in order to reduce dependency on Guava. The Guava library has frequently caused dependency
      * conflicts in the past.
      */
     private static String getIPv6UrlRepresentation(byte[] addressBytes) {
         // first, convert bytes to 16 bit chunks
         int[] hextets = new int[8];
         for (int i = 0; i < hextets.length; i++) {
             hextets[i] = (addressBytes[2 * i] & 0xFF) << 8 | (addressBytes[2 * i + 1] & 0xFF);
         }

         // now, find the sequence of zeros that should be compressed
         int bestRunStart = -1;
         int bestRunLength = -1;
         int runStart = -1;
         for (int i = 0; i < hextets.length + 1; i++) {
             if (i < hextets.length && hextets[i] == 0) {
                 if (runStart < 0) {
                     runStart = i;
                 }
             } else if (runStart >= 0) {
                 int runLength = i - runStart;
                 if (runLength > bestRunLength) {
                     bestRunStart = runStart;
                     bestRunLength = runLength;
                 }
                 runStart = -1;
             }
         }
         if (bestRunLength >= 2) {
             Arrays.fill(hextets, bestRunStart, bestRunStart + bestRunLength, -1);
         }

         // convert into text form
         StringBuilder buf = new StringBuilder(40);
         buf.append('[');

         boolean lastWasNumber = false;
         for (int i = 0; i < hextets.length; i++) {
             boolean thisIsNumber = hextets[i] >= 0;
             if (thisIsNumber) {
                 if (lastWasNumber) {
                     buf.append(':');
                 }
                 buf.append(Integer.toHexString(hextets[i]));
             } else {
                 if (i == 0 || lastWasNumber) {
                     buf.append("::");
                 }
             }
             lastWasNumber = thisIsNumber;
         }
         buf.append(']');
         return buf.toString();
     }

     // ------------------------------------------------------------------------
     //  Port range parsing
     // ------------------------------------------------------------------------

     /**
      * Returns an iterator over available ports defined by the range definition.
      *
      * @param rangeDefinition String describing a single port, a range of ports or multiple ranges.
      * @return Set of ports from the range definition
      * @throws NumberFormatException If an invalid string is passed.
      */
     public static Iterator<Integer> getPortRangeFromString(String rangeDefinition)
             throws NumberFormatException {
         final String[] ranges = rangeDefinition.trim().split(",");

         UnionIterator<Integer> iterators = new UnionIterator<>();

         for (String rawRange : ranges) {
             Iterator<Integer> rangeIterator;
             String range = rawRange.trim();
             int dashIdx = range.indexOf('-');
             if (dashIdx == -1) {
                 // only one port in range:
                 final int port = Integer.valueOf(range);
                 if (!isValidHostPort(port)) {
                     throw new IllegalConfigurationException(
                             "Invalid port configuration. Port must be between 0"
                                     + "and 65535, but was "
                                     + port
                                     + ".");
                 }
                 rangeIterator = Collections.singleton(Integer.valueOf(range)).iterator();
             } else {
                 // evaluate range
                 final int start = Integer.valueOf(range.substring(0, dashIdx));
                 if (!isValidHostPort(start)) {
                     throw new IllegalConfigurationException(
                             "Invalid port configuration. Port must be between 0"
                                     + "and 65535, but was "
                                     + start
                                     + ".");
                 }
                 final int end = Integer.valueOf(range.substring(dashIdx + 1, range.length()));
                 if (!isValidHostPort(end)) {
                     throw new IllegalConfigurationException(
                             "Invalid port configuration. Port must be between 0"
                                     + "and 65535, but was "
                                     + end
                                     + ".");
                 }
                 rangeIterator =
                         new Iterator<Integer>() {
                             int i = start;

                             @Override
                             public boolean hasNext() {
                                 return i <= end;
                             }

                             @Override
                             public Integer next() {
                                 return i++;
                             }

                             @Override
                             public void remove() {
                                 throw new UnsupportedOperationException("Remove not supported");
                             }
                         };
             }
             iterators.add(rangeIterator);
         }

         return iterators;
     }

     /**
      * Tries to allocate a socket from the given sets of ports.
      *
      * @param portsIterator A set of ports to choose from.
      * @param factory A factory for creating the SocketServer
      * @return null if no port was available or an allocated socket.
      */
     public static ServerSocket createSocketFromPorts(
             Iterator<Integer> portsIterator, SocketFactory factory) {
         while (portsIterator.hasNext()) {
             int port = portsIterator.next();
             LOG.debug("Trying to open socket on port {}", port);
             try {
                 return factory.createSocket(port);
             } catch (IOException | IllegalArgumentException e) {
                 if (LOG.isDebugEnabled()) {
                     LOG.debug("Unable to allocate socket on port", e);
                 } else {
                     LOG.info(
                             "Unable to allocate on port {}, due to error: {}",
                             port,
                             e.getMessage());
                 }
             }
         }
         return null;
     }

     /**
      * Returns the wildcard address to listen on all interfaces.
      *
      * @return Either 0.0.0.0 or :: depending on the IP setup.
      */
     public static String getWildcardIPAddress() {
         return WILDCARD_ADDRESS;
     }

     /** A factory for a local socket from port number. */
     @FunctionalInterface
     public interface SocketFactory {
         ServerSocket createSocket(int port) throws IOException;
     }

     /**
      * Check whether the given port is in right range when connecting to somewhere.
      *
      * @param port the port to check
      * @return true if the number in the range 1 to 65535
      */
     public static boolean isValidClientPort(int port) {
         return 1 <= port && port <= 65535;
     }

     /**
      * check whether the given port is in right range when getting port from local system.
      *
      * @param port the port to check
      * @return true if the number in the range 0 to 65535
      */
     public static boolean isValidHostPort(int port) {
         return 0 <= port && port <= 65535;
     }
 }
	/*
	* Licensed to the Apache Software Foundation (ASF) under one
	* or more contributor license agreements. See the NOTICE file
	* distributed with this work for additional information
	* regarding copyright ownership. The ASF licenses this file
	* to you under the Apache License, Version 2.0 (the
	* "License"); you may not use this file except in compliance
	* with the License. You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	package org.apache.flink.util;

	import org.apache.flink.annotation.Internal;
	import org.apache.flink.configuration.IllegalConfigurationException;

	import org.slf4j.Logger;
	import org.slf4j.LoggerFactory;
	import sun.net.util.IPAddressUtil;

	import java.io.IOException;
	import java.net.Inet4Address;
	import java.net.Inet6Address;
	import java.net.InetAddress;
	import java.net.InetSocketAddress;
	import java.net.MalformedURLException;
	import java.net.ServerSocket;
	import java.net.URL;
	import java.net.UnknownHostException;
	import java.util.Arrays;
	import java.util.Collections;
	import java.util.Iterator;

	/** Utility for various network related tasks (such as finding free ports). */
	@Internal
	public class NetUtils {

	private static final Logger LOG = LoggerFactory.getLogger(NetUtils.class);

	/** The wildcard address to listen on all interfaces (either 0.0.0.0 or ::). */
	private static final String WILDCARD_ADDRESS =
	new InetSocketAddress(0).getAddress().getHostAddress();

	/**
	* Turn a fully qualified domain name (fqdn) into a hostname. If the fqdn has multiple subparts
	* (separated by a period '.'), it will take the first part. Otherwise it takes the entire fqdn.
	*
	* @param fqdn The fully qualified domain name.
	* @return The hostname.
	*/
	public static String getHostnameFromFQDN(String fqdn) {
	if (fqdn == null) {
	throw new IllegalArgumentException("fqdn is null");
	}
	int dotPos = fqdn.indexOf('.');
	if (dotPos == -1) {
	return fqdn;
	} else {
	return fqdn.substring(0, dotPos);
	}
	}

	/**
	* Converts a string of the form "host:port" into an {@link URL}.
	*
	* @param hostPort The "host:port" string.
	* @return The converted URL.
	*/
	public static URL getCorrectHostnamePort(String hostPort) {
	return validateHostPortString(hostPort);
	}

	/**
	* Converts a string of the form "host:port" into an {@link InetSocketAddress}.
	*
	* @param hostPort The "host:port" string.
	* @return The converted InetSocketAddress.
	*/
	public static InetSocketAddress parseHostPortAddress(String hostPort) {
	URL url = validateHostPortString(hostPort);
	return new InetSocketAddress(url.getHost(), url.getPort());
	}

	/**
	* Validates if the given String represents a hostname:port.
	*
	* <p>Works also for ipv6.
	*
	* <p>See:
	* http://stackoverflow.com/questions/2345063/java-common-way-to-validate-and-convert-hostport-to-inetsocketaddress
	*
	* @return URL object for accessing host and port
	*/
	private static URL validateHostPortString(String hostPort) {
	try {
	URL u = new URL("http://" + hostPort);
	if (u.getHost() == null) {
	throw new IllegalArgumentException(
	"The given host:port ('" + hostPort + "') doesn't contain a valid host");
	}
	if (u.getPort() == -1) {
	throw new IllegalArgumentException(
	"The given host:port ('" + hostPort + "') doesn't contain a valid port");
	}
	return u;
	} catch (MalformedURLException e) {
	throw new IllegalArgumentException(
	"The given host:port ('" + hostPort + "') is invalid", e);
	}
	}

	// ------------------------------------------------------------------------
	// Lookup of to free ports
	// ------------------------------------------------------------------------

	/**
	* Find a non-occupied port.
	*
	* @return A non-occupied port.
	*/
	public static int getAvailablePort() {
	for (int i = 0; i < 50; i++) {
	try (ServerSocket serverSocket = new ServerSocket(0)) {
	int port = serverSocket.getLocalPort();
	if (port != 0) {
	return port;
	}
	} catch (IOException ignored) {
	}
	}

	throw new RuntimeException("Could not find a free permitted port on the machine.");
	}

	// ------------------------------------------------------------------------
	// Encoding of IP addresses for URLs
	// ------------------------------------------------------------------------

	/**
	* Returns an address in a normalized format for Akka. When an IPv6 address is specified, it
	* normalizes the IPv6 address to avoid complications with the exact URL match policy of Akka.
	*
	* @param host The hostname, IPv4 or IPv6 address
	* @return host which will be normalized if it is an IPv6 address
	*/
	public static String unresolvedHostToNormalizedString(String host) {
	// Return loopback interface address if host is null
	// This represents the behavior of {@code InetAddress.getByName } and RFC 3330
	if (host == null) {
	host = InetAddress.getLoopbackAddress().getHostAddress();
	} else {
	host = host.trim().toLowerCase();
	if (host.startsWith("[") && host.endsWith("]")) {
	String address = host.substring(1, host.length() - 1);
	if (IPAddressUtil.isIPv6LiteralAddress(address)) {
	host = address;
	}
	}
	}

	// normalize and valid address
	if (IPAddressUtil.isIPv6LiteralAddress(host)) {
	byte[] ipV6Address = IPAddressUtil.textToNumericFormatV6(host);
	host = getIPv6UrlRepresentation(ipV6Address);
	} else if (!IPAddressUtil.isIPv4LiteralAddress(host)) {
	try {
	// We don't allow these in hostnames
	Preconditions.checkArgument(!host.startsWith("."));
	Preconditions.checkArgument(!host.endsWith("."));
	Preconditions.checkArgument(!host.contains(":"));
	} catch (Exception e) {
	throw new IllegalConfigurationException("The configured hostname is not valid", e);
	}
	}

	return host;
	}

	/**
	* Returns a valid address for Akka. It returns a String of format 'host:port'. When an IPv6
	* address is specified, it normalizes the IPv6 address to avoid complications with the exact
	* URL match policy of Akka.
	*
	* @param host The hostname, IPv4 or IPv6 address
	* @param port The port
	* @return host:port where host will be normalized if it is an IPv6 address
	*/
	public static String unresolvedHostAndPortToNormalizedString(String host, int port) {
	Preconditions.checkArgument(isValidHostPort(port), "Port is not within the valid range,");
	return unresolvedHostToNormalizedString(host) + ":" + port;
	}

	/**
	* Encodes an IP address properly as a URL string. This method makes sure that IPv6 addresses
	* have the proper formatting to be included in URLs.
	*
	* @param address The IP address to encode.
	* @return The proper URL string encoded IP address.
	*/
	public static String ipAddressToUrlString(InetAddress address) {
	if (address == null) {
	throw new NullPointerException("address is null");
	} else if (address instanceof Inet4Address) {
	return address.getHostAddress();
	} else if (address instanceof Inet6Address) {
	return getIPv6UrlRepresentation((Inet6Address) address);
	} else {
	throw new IllegalArgumentException("Unrecognized type of InetAddress: " + address);
	}
	}

	/**
	* Encodes an IP address and port to be included in URL. in particular, this method makes sure
	* that IPv6 addresses have the proper formatting to be included in URLs.
	*
	* @param address The address to be included in the URL.
	* @param port The port for the URL address.
	* @return The proper URL string encoded IP address and port.
	*/
	public static String ipAddressAndPortToUrlString(InetAddress address, int port) {
	return ipAddressToUrlString(address) + ':' + port;
	}

	/**
	* Encodes an IP address and port to be included in URL. in particular, this method makes sure
	* that IPv6 addresses have the proper formatting to be included in URLs.
	*
	* @param address The socket address with the IP address and port.
	* @return The proper URL string encoded IP address and port.
	*/
	public static String socketAddressToUrlString(InetSocketAddress address) {
	if (address.isUnresolved()) {
	throw new IllegalArgumentException(
	"Address cannot be resolved: " + address.getHostString());
	}
	return ipAddressAndPortToUrlString(address.getAddress(), address.getPort());
	}

	/**
	* Normalizes and encodes a hostname and port to be included in URL. In particular, this method
	* makes sure that IPv6 address literals have the proper formatting to be included in URLs.
	*
	* @param host The address to be included in the URL.
	* @param port The port for the URL address.
	* @return The proper URL string encoded IP address and port.
	* @throws java.net.UnknownHostException Thrown, if the hostname cannot be translated into a
	* URL.
	*/
	public static String hostAndPortToUrlString(String host, int port) throws UnknownHostException {
	return ipAddressAndPortToUrlString(InetAddress.getByName(host), port);
	}

	/**
	* Creates a compressed URL style representation of an Inet6Address.
	*
	* <p>This method copies and adopts code from Google's Guava library. We re-implement this here
	* in order to reduce dependency on Guava. The Guava library has frequently caused dependency
	* conflicts in the past.
	*/
	private static String getIPv6UrlRepresentation(Inet6Address address) {
	return getIPv6UrlRepresentation(address.getAddress());
	}

	/**
	* Creates a compressed URL style representation of an Inet6Address.
	*
	* <p>This method copies and adopts code from Google's Guava library. We re-implement this here
	* in order to reduce dependency on Guava. The Guava library has frequently caused dependency
	* conflicts in the past.
	*/
	private static String getIPv6UrlRepresentation(byte[] addressBytes) {
	// first, convert bytes to 16 bit chunks
	int[] hextets = new int[8];
	for (int i = 0; i < hextets.length; i++) {
	hextets[i] = (addressBytes[2 * i] & 0xFF) << 8 \| (addressBytes[2 * i + 1] & 0xFF);
	}

	// now, find the sequence of zeros that should be compressed
	int bestRunStart = -1;
	int bestRunLength = -1;
	int runStart = -1;
	for (int i = 0; i < hextets.length + 1; i++) {
	if (i < hextets.length && hextets[i] == 0) {
	if (runStart < 0) {
	runStart = i;
	}
	} else if (runStart >= 0) {
	int runLength = i - runStart;
	if (runLength > bestRunLength) {
	bestRunStart = runStart;
	bestRunLength = runLength;
	}
	runStart = -1;
	}
	}
	if (bestRunLength >= 2) {
	Arrays.fill(hextets, bestRunStart, bestRunStart + bestRunLength, -1);
	}

	// convert into text form
	StringBuilder buf = new StringBuilder(40);
	buf.append('[');

	boolean lastWasNumber = false;
	for (int i = 0; i < hextets.length; i++) {
	boolean thisIsNumber = hextets[i] >= 0;
	if (thisIsNumber) {
	if (lastWasNumber) {
	buf.append(':');
	}
	buf.append(Integer.toHexString(hextets[i]));
	} else {
	if (i == 0 \|\| lastWasNumber) {
	buf.append("::");
	}
	}
	lastWasNumber = thisIsNumber;
	}
	buf.append(']');
	return buf.toString();
	}

	// ------------------------------------------------------------------------
	// Port range parsing
	// ------------------------------------------------------------------------

	/**
	* Returns an iterator over available ports defined by the range definition.
	*
	* @param rangeDefinition String describing a single port, a range of ports or multiple ranges.
	* @return Set of ports from the range definition
	* @throws NumberFormatException If an invalid string is passed.
	*/
	public static Iterator<Integer> getPortRangeFromString(String rangeDefinition)
	throws NumberFormatException {
	final String[] ranges = rangeDefinition.trim().split(",");

	UnionIterator<Integer> iterators = new UnionIterator<>();

	for (String rawRange : ranges) {
	Iterator<Integer> rangeIterator;
	String range = rawRange.trim();
	int dashIdx = range.indexOf('-');
	if (dashIdx == -1) {
	// only one port in range:
	final int port = Integer.valueOf(range);
	if (!isValidHostPort(port)) {
	throw new IllegalConfigurationException(
	"Invalid port configuration. Port must be between 0"
	+ "and 65535, but was "
	+ port
	+ ".");
	}
	rangeIterator = Collections.singleton(Integer.valueOf(range)).iterator();
	} else {
	// evaluate range
	final int start = Integer.valueOf(range.substring(0, dashIdx));
	if (!isValidHostPort(start)) {
	throw new IllegalConfigurationException(
	"Invalid port configuration. Port must be between 0"
	+ "and 65535, but was "
	+ start
	+ ".");
	}
	final int end = Integer.valueOf(range.substring(dashIdx + 1, range.length()));
	if (!isValidHostPort(end)) {
	throw new IllegalConfigurationException(
	"Invalid port configuration. Port must be between 0"
	+ "and 65535, but was "
	+ end
	+ ".");
	}
	rangeIterator =
	new Iterator<Integer>() {
	int i = start;

	@Override
	public boolean hasNext() {
	return i <= end;
	}

	@Override
	public Integer next() {
	return i++;
	}

	@Override
	public void remove() {
	throw new UnsupportedOperationException("Remove not supported");
	}
	};
	}
	iterators.add(rangeIterator);
	}

	return iterators;
	}

	/**
	* Tries to allocate a socket from the given sets of ports.
	*
	* @param portsIterator A set of ports to choose from.
	* @param factory A factory for creating the SocketServer
	* @return null if no port was available or an allocated socket.
	*/
	public static ServerSocket createSocketFromPorts(
	Iterator<Integer> portsIterator, SocketFactory factory) {
	while (portsIterator.hasNext()) {
	int port = portsIterator.next();
	LOG.debug("Trying to open socket on port {}", port);
	try {
	return factory.createSocket(port);
	} catch (IOException \| IllegalArgumentException e) {
	if (LOG.isDebugEnabled()) {
	LOG.debug("Unable to allocate socket on port", e);
	} else {
	LOG.info(
	"Unable to allocate on port {}, due to error: {}",
	port,
	e.getMessage());
	}
	}
	}
	return null;
	}

	/**
	* Returns the wildcard address to listen on all interfaces.
	*
	* @return Either 0.0.0.0 or :: depending on the IP setup.
	*/
	public static String getWildcardIPAddress() {
	return WILDCARD_ADDRESS;
	}

	/** A factory for a local socket from port number. */
	@FunctionalInterface
	public interface SocketFactory {
	ServerSocket createSocket(int port) throws IOException;
	}

	/**
	* Check whether the given port is in right range when connecting to somewhere.
	*
	* @param port the port to check
	* @return true if the number in the range 1 to 65535
	*/
	public static boolean isValidClientPort(int port) {
	return 1 <= port && port <= 65535;
	}

	/**
	* check whether the given port is in right range when getting port from local system.
	*
	* @param port the port to check
	* @return true if the number in the range 0 to 65535
	*/
	public static boolean isValidHostPort(int port) {
	return 0 <= port && port <= 65535;
	}
	}