java ssl echo server

SSLSocketEchoServer.java

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
import java.security.cert.Certificate;
import javax.net.ServerSocketFactory;
import javax.net.ssl.SSLPeerUnverifiedException;
import javax.net.ssl.SSLServerSocket;
import javax.net.ssl.SSLServerSocketFactory;
import javax.net.ssl.SSLSession;
import javax.net.ssl.SSLSocket;

public class SSLSocketEchoServer {
    public static void main(String[] args) throws IOException {
        System.setProperty("javax.net.ssl.keyStore", "C:\\Users\\Administrator\\Desktop\\work\\WIP\\client-cert-validation\\serverkeystore.p12");
        System.setProperty("javax.net.ssl.keyStorePassword", "password");
        System.setProperty("javax.net.ssl.trustStore", "C:\\Users\\Administrator\\Desktop\\work\\WIP\\client-cert-validation\\servertruststore.p12");
        System.setProperty("javax.net.ssl.trustStorePassword", "password");
        startServer(443);
    }

    static void startServer(int port) throws IOException {
        ServerSocketFactory factory = SSLServerSocketFactory.getDefault();
        try (SSLServerSocket listener = (SSLServerSocket) factory.createServerSocket(port)) {
            // enable client cert auth
            listener.setWantClientAuth(true);
            listener.setEnabledProtocols(new String[]{"TLSv1.2"});
            System.out.println("listening for messages...");
            while (true) {
                try (Socket socket = listener.accept()) {
                    InputStream is = new BufferedInputStream(socket.getInputStream());
                    byte[] data = new byte[2048];
                    int len = is.read(data);

                    String message = new String(data, 0, len);
                    OutputStream os = new BufferedOutputStream(socket.getOutputStream());
                    System.out.printf("server received %d bytes%n%s%n", len, message);
                    os.write("HTTP/1.1 200 OK\n".getBytes());
                    os.write("App: java std\n".getBytes());
                    os.write("Writer: mkp246\n".getBytes());
                    os.write("Server: my server\n".getBytes());
                    os.write("Content-Type: text/plain\n".getBytes());
                    os.write("\n".getBytes());
                    os.write("Request has been processed by the java server\r\n".getBytes());
                    if (socket instanceof SSLSocket) {
                        SSLSession session = ((SSLSocket) socket).getSession();
                        Certificate[] certs = getPeerCertsOrNull(session);
                        //print client cert detail to response
                        if (certs != null && certs.length != 0) {
                            os.write("client certificate chain:\r\n".getBytes());
                            int depth = 1;
                            for (Certificate cert : certs) {
                                os.write(("depth: " + depth++ + "\r\n").getBytes());
                                os.write(cert.toString().getBytes());
                                os.write("\r\n".getBytes());
                            }
                        }
                    }
                    os.flush();
                } catch (Exception e) {
                    System.out.println("error: " + e);
                }
            }
        }
    }

    private static Certificate[] getPeerCertsOrNull(SSLSession session) {
        try {
            return session.getPeerCertificates();
        } catch (SSLPeerUnverifiedException e) {
            return null;
        }
    }
}