What does the following code snippet do?

try (ServerSocket server = new ServerSocket(PORT)) {
    System.out.println("Listening...");
    while (true) {
        Socket service = server.accept();
        System.out.println("Connection established");
        ServerThread st = new ServerThread(service);
        st.start();
    }
} catch (IOException e) {
    System.out.println(e);
}