Java Utililty Methods HTTP Port Find

ServerSocket serverSocket = null;
try {
    serverSocket = new ServerSocket(0);
    return serverSocket.getLocalPort();
} finally {
    if (serverSocket != null) {
        serverSocket.close();

for (int port = min; port < max; port++) {
    try {
        new ServerSocket(port).close();
        return port;
    } catch (IOException e) {
throw new IllegalStateException("Could not find available port in range " + min + " to " + max);
...

synchronized (lock) {
    for (int i = minPort; i < maxPort; i++) {
        try {
            return new ServerSocket(i);
        } catch (IOException ex) {
throw new IOException("no available port found");

try (ServerSocket s = new ServerSocket(port)) {
    return s.getLocalPort();
} catch (IOException e) {
    throw e;

Determines the first available port, beginning at the specified port.

int limit = 500;
Socket socket;
while (limit > 0) {
    try {
        socket = new Socket("localhost", port);
        socket.close();
        limit--;
        port++;
...

for (int port = startPort; port < (endPort + 1); port++) {
    try {
        Socket socket = new Socket(InetAddress.getByName(hostname), port);
        socket.close();
    } catch (IOException e) {
        return port;
return 0;

int ports[] = new int[n];
ServerSocket[] sockets = new ServerSocket[n];
for (int i = 0; i < n; i++) {
    ServerSocket s = new ServerSocket(0);
    s.setReuseAddress(true);
    ports[i] = s.getLocalPort();
    sockets[i] = s;
for (int i = 0; i < n; i++)
    sockets[i].close();
return ports;

try (ServerSocket serverSocket = new ServerSocket(0)) {
    return serverSocket.getLocalPort();
} catch (IOException e) {
    throw new RuntimeException(e);

try {
    ServerSocket server = new ServerSocket(0);
    int port = server.getLocalPort();
    server.close();
    return port;
} catch (IOException e) {
    e.printStackTrace();
return 0;

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