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}. - * - *
{@code SocketUtils} was introduced in Spring Framework 4.0, primarily to - * assist in writing integration tests which start an external server on an - * available random port. However, these utilities make no guarantee about the - * subsequent availability of a given port and are therefore unreliable. Instead - * of using {@code SocketUtils} to find an available local port for a server, it - * is recommended that you rely on a server's ability to start on a random port - * that it selects or is assigned by the operating system. To interact with that - * server, you should query the server for the port it is currently using. - * - * @author Sam Brannen - * @author Ben Hale - * @author Arjen Poutsma - * @author Gunnar Hillert - * @author Gary Russell - * @since 4.0 - * @deprecated as of Spring Framework 5.3.16, to be removed in 6.0; see - * {@link SocketUtils class-level Javadoc} for details. - */ -@Deprecated -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.nanoTime()); - - - /** - * Although {@code SocketUtils} consists solely of static utility methods, - * this constructor is intentionally {@code public}. - *
Static methods from this class may be invoked from within XML - * configuration files using the Spring Expression Language (SpEL) and the - * following syntax. - *
<bean id="bean1" ... p:port="#{T(org.springframework.util.SocketUtils).findAvailableTcpPort(12000)}" /><bean id="socketUtils" class="org.springframework.util.SocketUtils" />
- * <bean id="bean1" ... p:port="#{socketUtils.findAvailableTcpPort(12000)}" />
- * <bean id="bean2" ... p:port="#{socketUtils.findAvailableTcpPort(30000)}" />Simple utility methods for working with network sockets — for example, + * for finding available ports on {@code localhost}. + * + *
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}. + * + *
{@code SocketUtils} was introduced in Spring Framework 4.0, primarily to + * assist in writing integration tests which start an external server on an + * available random port. However, these utilities make no guarantee about the + * subsequent availability of a given port and are therefore unreliable. Instead + * of using {@code SocketUtils} to find an available local port for a server, it + * is recommended that you rely on a server's ability to start on a random port + * that it selects or is assigned by the operating system. To interact with that + * server, you should query the server for the port it is currently using. + * + * @author Sam Brannen + * @author Ben Hale + * @author Arjen Poutsma + * @author Gunnar Hillert + * @author Gary Russell + * @since 4.0 + */ +public class TestSocketUtils { + + /** + * The default minimum value for port ranges used when finding an available + * socket port. + */ + private static final int PORT_RANGE_MIN = 1024; + + /** + * The default maximum value for port ranges used when finding an available + * socket port. + */ + private static final int PORT_RANGE_MAX = 65535; + + + private static final Random random = new Random(System.nanoTime()); + + + /** + * 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 findAvailablePort(PORT_RANGE_MIN, PORT_RANGE_MAX); + } + + /** + * 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 + */ + private static 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 equal to '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 TCP port in the range [%d, %d] after %d attempts", + minPort, maxPort, searchCounter)); + } + candidatePort = findRandomPort(minPort, maxPort); + searchCounter++; + } + while (!isPortAvailable(candidatePort)); + + return candidatePort; + } + + /** + * 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 static int findRandomPort(int minPort, int maxPort) { + int portRange = maxPort - minPort; + return minPort + random.nextInt(portRange + 1); + } + + /** + * Determine if the specified port for this {@code SocketType} is + * currently available on {@code localhost}. + */ + private static boolean isPortAvailable(int port) { + try { + ServerSocket serverSocket = ServerSocketFactory.getDefault().createServerSocket( + port, 1, InetAddress.getByName("localhost")); + serverSocket.close(); + return true; + } + catch (Exception ex) { + return false; + } + } + +}