SS.java

/*
 * Copyright (c) 2024 Georgios Politis
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */
import java.io.*;
import java.net.InetSocketAddress;
import java.net.ServerSocket;

/**
 * <p>
 * SS (SocketSend) is a super tiny Java class implementing a TCP server
 * that can be used to send/receive a file to/from a TCP client. It can
 * be useful in super restricted environments lacking netcat or even a
 * text editor but having a JDK installed. On the server:
 * </p>
 *
 * <pre>
 * {@code
 * $ cat <<EOF > SS.java
 * ... (copy/paste the code) ...
 * EOF
 * javac SS.java
 * java -cp . SS FILENAME
 * }
 * </pre>
 *
 * <p>
 * If FILENAME exists, then SS will go into TX mode, otherwise it
 * will go into RX mode. Then, on the client, you can send/receive the
 * file using more traditional tools like netcat.
 * </p>
 *
 * <p>
 * If you run SS in a k8s container, you can use kubectl to forward port
 * 1234 to connect to SS and transfer files between your computer and
 * the container.
 * </p>
 */
public class SS {

    public static void main(String ... argv) throws IOException {

        try (var ss = new ServerSocket()) {
            ss.bind(new InetSocketAddress("localhost", 1234));
            final var sock = ss.accept();
            System.out.println("Connected to " + sock.getInetAddress());
            final var f = new File(argv[0]);
            final var tx = f.isFile();
            final var buf = new byte[2048];
            try (
                final var in = tx
                    ? new BufferedInputStream(
                        new FileInputStream(argv[0]))
                    : sock.getInputStream();
                final var out = tx
                    ? sock.getOutputStream()
                    : new BufferedOutputStream(
                        new FileOutputStream(argv[0]));
            ) {
                var bytesRead = 0;
                var totalBytes = 0;
                while ((bytesRead = in.read(buf)) != -1) {
                    totalBytes += bytesRead;
                    out.write(buf, 0, bytesRead);
                }
                System.out.println(
                    (tx ? "TX" : "RX") + " bytes:"+ totalBytes);
            }
        }
    }
}