import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;

public class prog01RelayTCP {
	public static void main(String[] argv) throws Exception {
		final int NUM_BYTES = 80;

		String servip = "147.97.156.237";
		int servport = 11234;
		int clientport = 1234;

		if (argv.length >= 4)
		{
			try {
				// Read server port
				servport = Integer.parseInt(argv[0]);
			} catch (NumberFormatException e) {
				System.err.println("First argument must be an integer");
				System.exit(1);
			}

			// Read server IP address
			servip = argv[1];

			try {
				// Read relay port
				clientport = Integer.parseInt(argv[2]);
			} catch (NumberFormatException e) {
				System.err.println("Third argument must be an integer");
				System.exit(1);
			}

			try {
				// Read relay port
				int tmp = Integer.parseInt(argv[3]);
				// Change if argv[2] was actually the server port
				if( tmp != servport && clientport == servport )
					clientport = tmp;
			} catch (NumberFormatException e) {
				System.err.println("Fourth argument must be an integer");
				System.exit(1);
			}
		}

		servip = "localhost";
		servport = 11234;
		clientport = 1234;
		ServerSocket clientSS = null;
		byte[] buf = new byte[NUM_BYTES];
		try {
			// Open socket for client
			clientSS = new ServerSocket(clientport);
			while (true) {
				// Connect to server
				Socket serverSocket = new Socket(servip, servport);

				// Initialize server I/O
				Scanner servIn = new Scanner(serverSocket.getInputStream());
				PrintWriter servOut = new PrintWriter(serverSocket.getOutputStream(), true);

				// Connect to client
				try (Socket clientSocket = clientSS.accept()) {
					System.out.println("Connected to Client");

					// Initialize client I/O
					BufferedInputStream clientIn = new BufferedInputStream(clientSocket.getInputStream());
					PrintWriter clientOut = new PrintWriter(clientSocket.getOutputStream(), true);

					// Read input from client
					int nRead = clientIn.read(buf, 0, NUM_BYTES);

					// If the socket was closed, try again
					if (nRead <= 0) {
						// Close sockets
						clientIn.close();
						clientSocket.close();
						// Serve next one
						continue;
					}

					// Relay client data to server
					servOut.print(new String(buf));
					servOut.flush();
					System.out.println("CLIENT: " + new String(buf));

					// Relay server data to client
					String serverInput = servIn.nextLine();
					System.out.println("SERVER: " + serverInput);
					clientOut.println(serverInput);
				}

				serverSocket.close();
			}
		} catch (IOException ioEx) {
			System.out.println("Exception");
		} finally {
			clientSS.close();
		}
	}
}