client_get.java

用java实现的Tftp(Sftp)客户端与服务器程序。在这个程序中用到了一个“状态”的机制：客户端与服务器端在开始运行时有相同的状态

/**
 *协议的Client_Get状态.
 */
 import java.util.Timer;
 import java.io.FileInputStream;

public class Client_Get extends State {
	public static FileIOClass myfile;//将要存储的文件名
	public static ComClass Com;	   	 //用于传输
	Timer timer = new Timer(false);

	State doIt() {
		String addr, file;
		SimpleIO input = new SimpleIO(System.in);
		System.out.println("请输入文件名:\n");
		file = input.readString();
		System.out.println("请输入服务器IP:\n");
		addr = input.readString();
		Com = new ComClass(5555);
		FileIOClass myfile = new FileIOClass();
		byte filemode = myfile.createFile(file+".n");		 //创建一个新的文件
	    if(filemode==FileIOClass.already_exists||
	    	filemode==FileIOClass.create_failed) {	//打开不成功则返回Client_Put状态
			this.next_state = new Client_Get(); ///???
			return this.next_state;
	    }
		Com.writeOtherSiteAddress(addr); 	 //记下服务器IP
		byte num = 1 ;
		RWDelayClass Rdelay = new RWDelayClass(file);//发送RRQ的任务线程
		Rdelay.start();
		byte[] revbuf = Com.receivePacket() ;
		//如果不是DATA包或者对方相应的序号错
		while(revbuf[1]!=PacketCode.DATA ||revbuf[3]!=num) {
			System.out.println("收到了错误的DATA包,保持等待!");
			revbuf = Com.receivePacket() ;
		}
		Rdelay.task.cancel();//取消任务
		timer.purge();		 //移除任务
		myfile.writeToFile(revbuf);
		boolean endsLoop = false;
		while( endsLoop == false) {
			ACKDelayClass ACKdelay = new ACKDelayClass(num);//发送ACK的任务线程
			ACKdelay.start() ;
			if(num == 125) {
				num = 0 ;
			}
			revbuf = Com.receivePacket();
			while(revbuf[1]!=PacketCode.DATA||revbuf[3]!=num+(byte)1) {
				System.out.println("收到了错误的DATA的包,保持等待!");
				revbuf = Com.receivePacket() ;
			}			
			ACKdelay.task.cancel();
			timer.purge();
			myfile.writeToFile(revbuf);
			num += 1;
			if(revbuf[515] == 1) { //如果是最后一个包
				endsLoop = true ;
				myfile.endWrite() ;
			}
		}
		System.out.print("发送最后一个ACK包:");
		Com.sendPacketACK((byte)0,num);
		Com.closeSocket();
		this.next_state = new Idle();
		return this.next_state;
	}
	//发送读请求包的线程
	public class RWDelayClass extends java.lang.Thread {
		String filename ;
		RWResendClass task ;
		public RWDelayClass(String filename) {
			this.filename = filename ;
			task = new RWResendClass(filename);
		}
		public void run() {
            timer.schedule(task,0 ,2000);
		}
	}
	//超时重发读请求包的线程
	public class RWResendClass extends java.util.TimerTask {
		String filename ;
		final long time = System.currentTimeMillis();//date.getTime();
		public RWResendClass(String filename) {
			this.filename = filename ;
		}
		public void run() {
			Client_Get.Com.sendPacketRW(filename,(byte)0,PacketCode.RRQ); //发送数据报
			if (System.currentTimeMillis() - time >= 10000) {
            	this.cancel();
				timer.purge();
				System.out.println("等待超时!");
				System.exit(0);
            }
		}
	}
	
	//发送ACK的线程	
	public class ACKDelayClass extends java.lang.Thread {
		byte num ;
		ACKResendClass task ;
		public ACKDelayClass(byte num) {
			this.num = num ;
			task = new ACKResendClass(num);
		}
		public void run() {
            timer.schedule(task,0 ,2000);
		}
	}
	//超时重发ACK包的线程
	public class ACKResendClass extends java.util.TimerTask {
		byte num ;
		final long time = System.currentTimeMillis();//date.getTime();
		public ACKResendClass(byte num) {
			this.num = num ;
		}
		public void run() {
			Client_Get.Com.sendPacketACK((byte)0,num); //发送数据报
			if (System.currentTimeMillis() - time >= 10000) {
            	this.cancel();
				timer.purge();
 				System.out.println("等待超时!");
				System.exit(0);
           }
		}
	}
}