/*
* 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<
Integer>();
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;
}
}
}