simpclient.java

模拟SIMP协议间通信,需要配置JDK环境,整个程序对协议的生成是个很好的诠释

/**
 * <p>Title: Learning material for socket programming</p>
 * <p>Description: SIMP: Simple Instant Message Protocol. SIMP server records who is online, and redirects
 * messages to the correponding user. SIMP server waits on UDP port 8002, clients wait on UDP port 8003. SIMP server
 * supports following commands: user, pass, send, ask, sendfile, bye.
 * user command allowing a user to send his/her username to the server.
 * pass command allowing a user to send his/her password to the server. Only the user command executed should
 * the pass command be invoked. If the user-pass pair matches a record in the user list, the user is ready to working.
 * ask command asking the server if a specific user is online, usage: ask user. If the user is online, the server
 * returns yes, otherwise no.
 * send command sending a message to a user, usage: send user. At the end of message, a single period is needed.
 * sendfile command send a file to a user, usage: sendfile user file_full_path.
 * NOTE: both messages and files should not exceed 512 bytes.
 * Datagram format:
 *    user command: SIMP user username1
 *    pass command: SIMP pass username1 password
 *    ask command: SIMP ask username1 username2
 *    send command: SIMP send username1 username2 0-512 bytes message
 *    sendfile command: SIMP sendfile username1 username2 filename 0-512 bytes file data
 *    bye command: SIMP bye username1
 * Server response:
 *    SIMP status_code
 * status_code: 100, OK, 200, sending success, 300, client error, 400 server error.</p>
 * <p>Copyright: Copyright (c) 2005</p>
 * <p>Company: </p>
 * @author BLiu
 * @version 0.1
 */

import java.net.*;
import java.io.*;
import java.util.*;

public class SIMPClient {
	String user;

	SocketAddress sa;

	DatagramSocket client;

	boolean login = false;

	public SIMPClient(String user, String serverIP) {
		try {
			sa = new InetSocketAddress(serverIP, 8002);
			client = new DatagramSocket();
		} catch (Exception e) {
			e.printStackTrace(System.out);
		}
		this.user = user;
		while (true) {
			byte[] buf = new byte[100];
			System.out.print("#");
			try {
				System.in.read(buf);
				if (buf[0] == '?')
					printHelp();
				else {
					handleInput(buf);
				}
			} catch (Exception e) {
				e.printStackTrace(System.out);
			}
		}
	}

	public static void main(String[] args) {
		if (args.length != 2) {
			System.out
					.println("ERROR!! USAGE: java SIMPClient username serverIP");
			System.exit(1);
		}
		SIMPClient SIMPClient1 = new SIMPClient(args[0], args[1]);
	}

	void sendToServer(String s) {
		try {
			DatagramPacket dp = new DatagramPacket(s.getBytes(), s.length(), sa);
			client.send(dp);
		} catch (Exception e) {
			e.printStackTrace(System.out);
		}
	}

	void printHelp() {
		System.out.println("Commands:");
		System.out.println("pass passwd : login to the server");
		System.out
				.println("send user : send a message to user, end with a single . at the begin of a line");
		System.out
				.println("sendfile user file_full_path : send a file of less than 512 bytes to user");
		System.out.println("ask user : ask server whether user is online ");
		System.out.println("bye : quit this session");
		System.out.println("? : print this help");
	}

	void handleInput(byte[] buf) throws Exception {
		String[] tokens = new String(buf).trim().split(" ");
		if (tokens[0].equals("pass")) {
			handlePass(tokens[1]);
		} else if (tokens[0].equals("send")) {
			handleSend(tokens[1]);
		} else if (tokens[0].equals("ask")) {
			sendToServer("SIMP ask " + user + " " + tokens[1]);
		} else if (tokens[0].equals("sendfile")) {
			handleSendfile(tokens[1], tokens[2]);
		} else if (tokens[0].equals("bye")) {
			sendToServer("SIMP bye " + user);
			System.out.print("SIMP bye " + user);
			System.exit(0);
		}
	}

	void handlePass(String pass) {
		try {
			sendToServer("SIMP pass " + user + " " + pass);
			DatagramPacket dp = new DatagramPacket(new byte[2048], 2048);
			client.receive(dp);
			String res = new String(dp.getData()).trim();
			if (res.equals("SIMP 100")) {// login sucessful.
				login = true;
				System.out.println("login sucessful");
				// start the helper thread.
				new ClientHelper(client).start();
			} else {
				System.out.println("bad username or password");
			}
		} catch (Exception e) {
			e.printStackTrace(System.out);
		}
	}

	void handleSend(String u) {
		StringBuffer s = new StringBuffer("SIMP send ");
		s.append(user);
		s.append(' ');
		s.append(u);
		s.append(' ');
		while (true) {
			try {
				byte[] buf = new byte[100];
				System.in.read(buf);
				s.append(new String(buf));
				if (buf[0] == '.')
					break;
			} catch (Exception e) {
				e.printStackTrace(System.out);
			}
		}
		System.out.println(s);
		sendToServer(s.toString());
	}

	void handleSendfile(String u, String f) throws Exception {
		StringBuffer s = new StringBuffer("SIMP sendfile ");
		s.append(user);
		s.append(' ');
		s.append(u);
		s.append(' ');
		s.append(f);
		s.append(' ');
		File file = new File(f);
		FileInputStream fis = new FileInputStream(file);
		DataInputStream dis = new DataInputStream(fis);
		byte[] buf = new byte[2048];
		int num = dis.read(buf);
		while (num != (-1)) {
			dis.read(buf, 0, num);
			s.append(new String(buf));
			dis.skip(num);
			num = dis.read(buf);
		}
		dis.close();
		System.out.println("The file "+f+"is send!");
		sendToServer(s.toString());
	}

	class ClientHelper extends Thread {

		DatagramSocket ds;

		ClientHelper(DatagramSocket ds) {
			this.ds = ds;
		}

		public void run() {
			try {
				while (true) {
					DatagramPacket dp = new DatagramPacket(new byte[2048], 2048);
					ds.receive(dp);
					String[] tokens = new String(dp.getData()).trim()
							.split(" ");
					if (tokens[1].equals("sendfile")) {
						StringBuffer s = new StringBuffer();
						System.out.println("Please input savefilepath:");
						while (true) {
							try {
								byte[] buf = new byte[100];
								System.in.read(buf);

								if (buf[0] == '$')
									break;
								s.append(new String(buf));
							} catch (Exception e) {
								e.printStackTrace(System.out);
							}
						}

						String[] t = new String(s).trim().split(" ");
						
						File file = new File(t[0]);
						file.createNewFile();
						FileOutputStream fos = new FileOutputStream(file);
						DataOutputStream dos = new DataOutputStream(fos);
						String str = "";
						for (int i = 0; i < 6; i++)
							str = str + tokens[i];
						dos.write(dp.getData(), str.length(),
								dp.getData().length - str.length());
						dos.close();
						System.out.println("The file is save at " + t[0]);
					} else
						System.out.println(new String(dp.getData()));
				}
			} catch (Exception e) {
				e.printStackTrace(System.out);
			}
		}
	}
}