Mega Code Archive
Available Port Finder
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/*
* 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.
*
*/
import java.io.IOException;
import java.net.DatagramSocket;
import java.net.ServerSocket;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.TreeSet;
/**
* Finds currently available server ports.
*
* @author The Apache MINA Project (dev@mina.apache.org)
* @version $Rev: 576217 $
* @see <a href="http://www.iana.org/assignments/port-numbers">IANA.org</a>
*/
public class AvailablePortFinder {
/**
* The minimum number of server port number.
*/
public static final int MIN_PORT_NUMBER = 1;
/**
* The maximum number of server port number.
*/
public static final int MAX_PORT_NUMBER = 49151;
/**
* Creates a new instance.
*/
private AvailablePortFinder() {
}
/**
* Returns the {@link Set} of currently available port numbers
* ({@link Integer}). This method is identical to
* <code>getAvailablePorts(MIN_PORT_NUMBER, MAX_PORT_NUMBER)</code>.
*
* WARNING: this can take a very long time.
*/
public static Set<Integer> getAvailablePorts() {
return getAvailablePorts(MIN_PORT_NUMBER, MAX_PORT_NUMBER);
}
/**
* Gets the next available port starting at the lowest port number.
*
* @throws NoSuchElementException if there are no ports available
*/
public static int getNextAvailable() {
return getNextAvailable(MIN_PORT_NUMBER);
}
/**
* Gets the next available port starting at a port.
*
* @param fromPort the port to scan for availability
* @throws NoSuchElementException if there are no ports available
*/
public static int getNextAvailable(int fromPort) {
if (fromPort < MIN_PORT_NUMBER || fromPort > MAX_PORT_NUMBER) {
throw new IllegalArgumentException("Invalid start port: "
+ fromPort);
}
for (int i = fromPort; i <= MAX_PORT_NUMBER; i++) {
if (available(i)) {
return i;
}
}
throw new NoSuchElementException("Could not find an available port "
+ "above " + fromPort);
}
/**
* Checks to see if a specific port is available.
*
* @param port the port to check for availability
*/
public static boolean available(int port) {
if (port < MIN_PORT_NUMBER || port > MAX_PORT_NUMBER) {
throw new IllegalArgumentException("Invalid start port: " + port);
}
ServerSocket ss = null;
DatagramSocket ds = null;
try {
ss = new ServerSocket(port);
ss.setReuseAddress(true);
ds = new DatagramSocket(port);
ds.setReuseAddress(true);
return true;
} catch (IOException e) {
} finally {
if (ds != null) {
ds.close();
}
if (ss != null) {
try {
ss.close();
} catch (IOException e) {
/* should not be thrown */
}
}
}
return false;
}
/**
* Returns the {@link Set} of currently avaliable port numbers ({@link Integer})
* between the specified port range.
*
* @throws IllegalArgumentException if port range is not between
* {@link #MIN_PORT_NUMBER} and {@link #MAX_PORT_NUMBER} or
* <code>fromPort</code> if greater than <code>toPort</code>.
*/
public static Set<Integer> getAvailablePorts(int fromPort, int toPort) {
if (fromPort < MIN_PORT_NUMBER || toPort > MAX_PORT_NUMBER
|| fromPort > toPort) {
throw new IllegalArgumentException("Invalid port range: "
+ fromPort + " ~ " + toPort);
}
Set<Integer> result = new TreeSet<Integer>();
for (int i = fromPort; i <= toPort; i++) {
ServerSocket s = null;
try {
s = new ServerSocket(i);
result.add(new Integer(i));
} catch (IOException e) {
} finally {
if (s != null) {
try {
s.close();
} catch (IOException e) {
/* should not be thrown */
}
}
}
}
return result;
}
}
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