How to find an available (free) TCP port in Java

gistfile1.java

	/**
	 * Returns a free port number on localhost.
	 * 
	 * Heavily inspired from org.eclipse.jdt.launching.SocketUtil (to avoid a dependency to JDT just because of this).
	 * Slightly improved with close() missing in JDT. And throws exception instead of returning -1.
	 * 
	 * @return a free port number on localhost
	 * @throws IllegalStateException if unable to find a free port
	 */
	private static int findFreePort() {
		ServerSocket socket = null;
		try {
			socket = new ServerSocket(0);
			socket.setReuseAddress(true);
			int port = socket.getLocalPort();
			try {
				socket.close();
			} catch (IOException e) {
				// Ignore IOException on close()
			}
			return port;
		} catch (IOException e) { 
		} finally {
			if (socket != null) {
				try {
					socket.close();
				} catch (IOException e) {
				}
			}
		}
		throw new IllegalStateException("Could not find a free TCP/IP port to start embedded Jetty HTTP Server on");
	}

What about this:

        try (ServerSocket socket = new ServerSocket(0)) {
            socket.setReuseAddress(true);
            return socket.getLocalPort();
        }

Not exactly equivalent, but way more concise. WDYT?

This wont work well if you need need multiple free ports - or have concurrent junit runs.

Need to wrap it as a class that extends org.junit.rules.ExternalResource.

Lines 16 to 20 are not necessary since the code in the finally block will be called anyway.