/*
* Copyright 2002-2016 the original author or authors.
*
* Licensed 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.springframework.util;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.util.Random;
import java.util.SortedSet;
import java.util.TreeSet;
import javax.net.ServerSocketFactory;
/**
* Simple utility methods for working with network sockets — for example,
* for finding available ports on {@code localhost}.
*
* <p>Within this class, a TCP port refers to a port for a {@link ServerSocket};
* whereas, a UDP port refers to a port for a {@link DatagramSocket}.
*
* @author Sam Brannen
* @author Ben Hale
* @author Arjen Poutsma
* @author Gunnar Hillert
* @author Gary Russell
* @since 4.0
*/
public class SocketUtils {
/**
* The default minimum value for port ranges used when finding an available
* socket port.
*/
public static final int PORT_RANGE_MIN = 1024;
/**
* The default maximum value for port ranges used when finding an available
* socket port.
*/
public static final int PORT_RANGE_MAX = 65535;
private static final Random random = new Random(System.currentTimeMillis());
/**
* Although {@code SocketUtils} consists solely of static utility methods,
* this constructor is intentionally {@code public}.
* <h4>Rationale</h4>
* <p>Static methods from this class may be invoked from within XML
* configuration files using the Spring Expression Language (SpEL) and the
* following syntax.
* <pre><code><bean id="bean1" ... p:port="#{T(org.springframework.util.SocketUtils).findAvailableTcpPort(12000)}" /></code></pre>
* If this constructor were {@code private}, you would be required to supply
* the fully qualified class name to SpEL's {@code T()} function for each usage.
* Thus, the fact that this constructor is {@code public} allows you to reduce
* boilerplate configuration with SpEL as can be seen in the following example.
* <pre><code><bean id="socketUtils" class="org.springframework.util.SocketUtils" />
* <bean id="bean1" ... p:port="#{socketUtils.findAvailableTcpPort(12000)}" />
* <bean id="bean2" ... p:port="#{socketUtils.findAvailableTcpPort(30000)}" /></code></pre>
*/
public SocketUtils() {
/* no-op */
}
/**
* Find an available TCP port randomly selected from the range
* [{@value #PORT_RANGE_MIN}, {@value #PORT_RANGE_MAX}].
* @return an available TCP port number
* @throws IllegalStateException if no available port could be found
*/
public static int findAvailableTcpPort() {
return findAvailableTcpPort(PORT_RANGE_MIN);
}
/**
* Find an available TCP port randomly selected from the range
* [{@code minPort}, {@value #PORT_RANGE_MAX}].
* @param minPort the minimum port number
* @return an available TCP port number
* @throws IllegalStateException if no available port could be found
*/
public static int findAvailableTcpPort(int minPort) {
return findAvailableTcpPort(minPort, PORT_RANGE_MAX);
}
/**
* Find an available TCP port randomly selected from the range
* [{@code minPort}, {@code maxPort}].
* @param minPort the minimum port number
* @param maxPort the maximum port number
* @return an available TCP port number
* @throws IllegalStateException if no available port could be found
*/
public static int findAvailableTcpPort(int minPort, int maxPort) {
return SocketType.TCP.findAvailablePort(minPort, maxPort);
}
/**
* Find the requested number of available TCP ports, each randomly selected
* from the range [{@value #PORT_RANGE_MIN}, {@value #PORT_RANGE_MAX}].
* @param numRequested the number of available ports to find
* @return a sorted set of available TCP port numbers
* @throws IllegalStateException if the requested number of available ports could not be found
*/
public static SortedSet<Integer> findAvailableTcpPorts(int numRequested) {
return findAvailableTcpPorts(numRequested, PORT_RANGE_MIN, PORT_RANGE_MAX);
}
/**
* Find the requested number of available TCP ports, each randomly selected
* from the range [{@code minPort}, {@code maxPort}].
* @param numRequested the number of available ports to find
* @param minPort the minimum port number
* @param maxPort the maximum port number
* @return a sorted set of available TCP port numbers
* @throws IllegalStateException if the requested number of available ports could not be found
*/
public static SortedSet<Integer> findAvailableTcpPorts(int numRequested, int minPort, int maxPort) {
return SocketType.TCP.findAvailablePorts(numRequested, minPort, maxPort);
}
/**
* Find an available UDP port randomly selected from the range
* [{@value #PORT_RANGE_MIN}, {@value #PORT_RANGE_MAX}].
* @return an available UDP port number
* @throws IllegalStateException if no available port could be found
*/
public static int findAvailableUdpPort() {
return findAvailableUdpPort(PORT_RANGE_MIN);
}
/**
* Find an available UDP port randomly selected from the range
* [{@code minPort}, {@value #PORT_RANGE_MAX}].
* @param minPort the minimum port number
* @return an available UDP port number
* @throws IllegalStateException if no available port could be found
*/
public static int findAvailableUdpPort(int minPort) {
return findAvailableUdpPort(minPort, PORT_RANGE_MAX);
}
/**
* Find an available UDP port randomly selected from the range
* [{@code minPort}, {@code maxPort}].
* @param minPort the minimum port number
* @param maxPort the maximum port number
* @return an available UDP port number
* @throws IllegalStateException if no available port could be found
*/
public static int findAvailableUdpPort(int minPort, int maxPort) {
return SocketType.UDP.findAvailablePort(minPort, maxPort);
}
/**
* Find the requested number of available UDP ports, each randomly selected
* from the range [{@value #PORT_RANGE_MIN}, {@value #PORT_RANGE_MAX}].
* @param numRequested the number of available ports to find
* @return a sorted set of available UDP port numbers
* @throws IllegalStateException if the requested number of available ports could not be found
*/
public static SortedSet<Integer> findAvailableUdpPorts(int numRequested) {
return findAvailableUdpPorts(numRequested, PORT_RANGE_MIN, PORT_RANGE_MAX);
}
/**
* Find the requested number of available UDP ports, each randomly selected
* from the range [{@code minPort}, {@code maxPort}].
* @param numRequested the number of available ports to find
* @param minPort the minimum port number
* @param maxPort the maximum port number
* @return a sorted set of available UDP port numbers
* @throws IllegalStateException if the requested number of available ports could not be found
*/
public static SortedSet<Integer> findAvailableUdpPorts(int numRequested, int minPort, int maxPort) {
return SocketType.UDP.findAvailablePorts(numRequested, minPort, maxPort);
}
private enum SocketType {
TCP {
@Override
protected boolean isPortAvailable(int port) {
try {
ServerSocket serverSocket = ServerSocketFactory.getDefault().createServerSocket(
port, 1, InetAddress.getByName("localhost"));
serverSocket.close();
return true;
}
catch (Exception ex) {
return false;
}
}
},
UDP {
@Override
protected boolean isPortAvailable(int port) {
try {
DatagramSocket socket = new DatagramSocket(port, InetAddress.getByName("localhost"));
socket.close();
return true;
}
catch (Exception ex) {
return false;
}
}
};
/**
* Determine if the specified port for this {@code SocketType} is
* currently available on {@code localhost}.
*/
protected abstract boolean isPortAvailable(int port);
/**
* Find a pseudo-random port number within the range
* [{@code minPort}, {@code maxPort}].
* @param minPort the minimum port number
* @param maxPort the maximum port number
* @return a random port number within the specified range
*/
private int findRandomPort(int minPort, int maxPort) {
int portRange = maxPort - minPort;
return minPort + random.nextInt(portRange + 1);
}
/**
* Find an available port for this {@code SocketType}, randomly selected
* from the range [{@code minPort}, {@code maxPort}].
* @param minPort the minimum port number
* @param maxPort the maximum port number
* @return an available port number for this socket type
* @throws IllegalStateException if no available port could be found
*/
int findAvailablePort(int minPort, int maxPort) {
Assert.isTrue(minPort > 0, "'minPort' must be greater than 0");
Assert.isTrue(maxPort >= minPort, "'maxPort' must be greater than or equals 'minPort'");
Assert.isTrue(maxPort <= PORT_RANGE_MAX, "'maxPort' must be less than or equal to " + PORT_RANGE_MAX);
int portRange = maxPort - minPort;
int candidatePort;
int searchCounter = 0;
do {
if (++searchCounter > portRange) {
throw new IllegalStateException(String.format(
"Could not find an available %s port in the range [%d, %d] after %d attempts",
name(), minPort, maxPort, searchCounter));
}
candidatePort = findRandomPort(minPort, maxPort);
}
while (!isPortAvailable(candidatePort));
return candidatePort;
}
/**
* Find the requested number of available ports for this {@code SocketType},
* each randomly selected from the range [{@code minPort}, {@code maxPort}].
* @param numRequested the number of available ports to find
* @param minPort the minimum port number
* @param maxPort the maximum port number
* @return a sorted set of available port numbers for this socket type
* @throws IllegalStateException if the requested number of available ports could not be found
*/
SortedSet<Integer> findAvailablePorts(int numRequested, int minPort, int maxPort) {
Assert.isTrue(minPort > 0, "'minPort' must be greater than 0");
Assert.isTrue(maxPort > minPort, "'maxPort' must be greater than 'minPort'");
Assert.isTrue(maxPort <= PORT_RANGE_MAX, "'maxPort' must be less than or equal to " + PORT_RANGE_MAX);
Assert.isTrue(numRequested > 0, "'numRequested' must be greater than 0");
Assert.isTrue((maxPort - minPort) >= numRequested,
"'numRequested' must not be greater than 'maxPort' - 'minPort'");
SortedSet<Integer> availablePorts = new TreeSet<>();
int attemptCount = 0;
while ((++attemptCount <= numRequested + 100) && availablePorts.size() < numRequested) {
availablePorts.add(findAvailablePort(minPort, maxPort));
}
if (availablePorts.size() != numRequested) {
throw new IllegalStateException(String.format(
"Could not find %d available %s ports in the range [%d, %d]",
numRequested, name(), minPort, maxPort));
}
return availablePorts;
}
}
}