UDPServer.java

package udp3;

import static java.nio.charset.StandardCharsets.UTF_8;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketAddress;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.channels.DatagramChannel;
import java.util.Scanner;

public class UDPServer {
	
	// HTTP request
	static String method;
	static String url;
	static String requestVersion;
	static String requestHeader;
	static String requestEntityBody;
			
	// HTTP response
	static String responseVersion = "HTTP/1.0";
	static String statusCode;
	static String phrase;
	static String responseHeader;
	static String responseEntityBody;
	static String serverResponse;
	
	public void listenAndServe(boolean verbose, int port, String directory) throws IOException {

		try (DatagramChannel channel = DatagramChannel.open()) {
			channel.bind(new InetSocketAddress(port));

			System.out.println("" + channel.getLocalAddress());

			ByteBuffer buf = ByteBuffer
					.allocate(Packet.MAX_LEN)
					.order(ByteOrder.BIG_ENDIAN);

			for (; ; ) {
				buf.clear();
				SocketAddress router = channel.receive(buf);

				// Parse a packet from the received raw data.
				buf.flip();
				Packet packet = Packet.fromBuffer(buf);
				buf.flip();
				
				// DATA REQUEST 
				if(packet.getType() == 0) { 
					
					reset();
					
					String[] splitClientPayload;
					String[] splitClientPayload2;
				
					String payload = new String(packet.getPayload(), UTF_8);
					
					System.out.println(payload);
					System.out.println(" ");
					
					splitClientPayload = payload.split(" ");
					splitClientPayload2 = splitClientPayload[2].split("\\\\r\\\\n");
					
					if(splitClientPayload2.length > 2) { 
						requestEntityBody = splitClientPayload2[3];
					}
					
					method = splitClientPayload[0];
					url = splitClientPayload[1];
					requestHeader = splitClientPayload2[1];
					
					if(method.equals("get") || method.equals("GET")) { 
						if(url.equals("/") & url.length() == 1) { 
							getFileResponse(directory);
						}
						
						else { 
							getResponse(directory, url);
						}
					}
					
					else {
						postResponse(directory, url, requestEntityBody);
					} 
					
					serverResponse = responseVersion + " " + statusCode + " " + phrase + "\\r\\n" + responseHeader + "\\r\\n" + "\\r\\n" + responseEntityBody;

					System.out.println("SERVER: Sending this message to client: " + serverResponse);
					
					Packet resp = packet.toBuilder()
							.setPayload(serverResponse.getBytes())
							.create();
					channel.send(resp.toBuffer(), router);
				}
				
				// CONNECTION REQUEST
				if(packet.getType() == 1) { 
					System.out.println("SERVER: Sending back syn ack");
					Packet resp = packet.toBuilder()
							.setType(2)
							.create();
					channel.send(resp.toBuffer(), router);
				}
				
				// CLOSING REQUEST
				if(packet.getType() == 3) { 
					System.out.println("SERVER: Sending back FYN-ACK");
					Packet resp = packet.toBuilder()
							.setType(4)
							.create();
					channel.send(resp.toBuffer(), router);
				}
 
			}
		}
	}
	
	// ---------------------------SUPPORTING METHODS-----------------------------------
	
	// Get File method 
	public static void getFileResponse(String directory) {
		
		File fileDirectory = new File(directory);
		File[] listFiles = fileDirectory.listFiles();
		
		for (File file : listFiles)
        {
            if (file.isFile())
            {
                responseEntityBody += "\n" + file.getName().toString() + "\n";
            }
        }
		
		statusCode = "200";
        phrase = "OK";
        responseHeader = requestHeader;
	}
	
	// Get method
	public static void getResponse(String directory, String url) {
		
		System.out.println("Checking if file exists...");
		
		File file = new File(directory+url);
		
		// Check if file exists in the directory
		if(file.exists()) {
			try { 
				System.out.println("Trying to read from files...");
				readFile(directory, url);
		
			}
			
			catch(Exception e) { 
				e.getMessage();
			}
		}
		
		else {
			statusCode = "404";
			phrase = "Not Found";
		}
	}
	
	// Post method
	public static void postResponse(String directory, String url, String requestEntityBody) { 
		File file = new File(directory+url);
		
		if(file.exists()) { 
			
			PrintWriter pw = null;
			
			try {
				pw = new PrintWriter(file);
			} catch (FileNotFoundException e) {
				e.printStackTrace();
			}
			
			pw.print(requestEntityBody);
			pw.close();
			
			statusCode = "200";
            phrase = "OK";
            responseHeader = requestHeader + "\\r\\n" + "Content-length: " + requestEntityBody.length() + "\\r\\n" + "Content-Type: text/html";
            responseEntityBody = requestEntityBody;
		}
		
		else {
			
			try {
				file.createNewFile();
			} catch (IOException e) {
				e.printStackTrace();
			}
			
			PrintWriter pw = null;
			
			try {
				pw = new PrintWriter(file);
			} catch (FileNotFoundException e) {
				e.printStackTrace();
			}
			
			pw.print(requestEntityBody);
			pw.close();
			
			statusCode = "201";
            phrase = "Created";
            responseHeader = requestHeader + "\\r\\n" + "Content-length: " + requestEntityBody.length() + "\\r\\n" + "Content-Type: text/html";
            responseEntityBody = requestEntityBody;
		}
		
	}
	
	// Reads the selected file
	public static void readFile(String directory, String url) { 
		System.out.println("Reading from the file...");
		
		Scanner keyboard = null;
		String text = "";
		
		try {
			keyboard = new Scanner(new File("/Users/mushfiquranik/Documents/Java Workspace/TestFolder/" + url));
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		while(keyboard.hasNext()) { 
			text += keyboard.nextLine() + "\n";
		}
		
		
		statusCode = "200";
        phrase = "OK";
        responseEntityBody = text;
        responseHeader = requestHeader + "\\r\\n" + "Content-Length:" + responseEntityBody.length() + "\\r\\n" + "Content-Type: text/html";
	}
	
	// Reset all the values to null
	public static void reset() { 
		// HTTP request
		method = null;
		url = null;
	    requestVersion = null;
		requestHeader = null;
		requestEntityBody = null;
		
		// HTTP response
		responseVersion = "HTTP/1.0";
		statusCode = null;
		phrase = null;
		responseHeader = null;
		responseEntityBody = null;
		serverResponse = null;
	}
}