diff --git a/client.java b/client.java
new file mode 100644
index 0000000..f262703
--- /dev/null
+++ b/client.java
@@ -0,0 +1,143 @@
+package TCP;
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.OutputStreamWriter;
+import java.net.Socket;
+import java.util.Random;
+import java.awt.*;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+
+import TCP.MySegment;
+
+public class Client {
+	public static int port=8888;
+	static long startTime=0;
+	static long finishTime=0;
+	static int seq=0;
+	static int ackno=0;
+	static int window=5;
+	static byte[] content=new byte[50];
+	static int acked=-1;
+	static boolean ack=false;
+	static boolean pauseflag=true;
+	static int error=0;
+	
+	static Frame frame =new Frame("Client");
+	static Label label1=new Label("received:");
+    static Label label2=new Label("Current window size: "+window);
+    static Choice windowSize=new Choice();
+    static Button start=new Button("Set");
+	
+	//使三分之一的包出错
+	public static void send(String content,OutputStreamWriter osw) throws IOException, InterruptedException
+	{
+		Random random=new Random();
+		if(random.nextInt(100)>30)
+		{
+			osw.write(content+"\n");
+			osw.flush();
+			Thread.sleep(200);
+		}
+		else
+		{
+			content="00"+content.substring(2);
+			osw.write(content+"\n");
+			osw.flush();
+			Thread.sleep(200);
+		}
+	}
+	
+	public static void main(String []args) throws IOException, InterruptedException
+	{
+
+		
+		
+		frame.setLayout(new GridLayout(4,3));
+		frame.setTitle("Client");
+		frame.setSize(500, 150);
+		frame.setLocation(800, 300);
+		frame.setAlwaysOnTop(true);
+        frame.setVisible(true);
+        
+        frame.add(label1);
+        frame.add(label2);
+        
+        windowSize.add("1");
+        windowSize.add("3");
+        windowSize.add("5");
+        windowSize.add("7");
+        windowSize.add("9");
+        windowSize.select(2);
+        frame.add(windowSize);
+        
+        start.setLocation(2, 1);
+        frame.add(start);
+        start.addActionListener(new ButtonHandler());
+        
+        
+		Socket socket=null;
+		for(int i=0;i<50;i++)
+		{
+			content[i]=-1;
+		}
+		try
+		{
+			socket=new Socket("127.0.0.1",port);
+		}
+		catch(Exception e)
+		{
+			e.printStackTrace();
+		}
+		OutputStreamWriter osw=new OutputStreamWriter(socket.getOutputStream());
+		BufferedReader br=new BufferedReader(new InputStreamReader(socket.getInputStream()));
+		StringBuilder receivedcache=new StringBuilder(" ");
+		for(int i=0;i<50;i++) receivedcache.append(' ');
+		startTime=System.currentTimeMillis();
+		while(true)
+		{
+			String got=br.readLine();
+			String[] segkey=got.split("--");
+			MySegment seg=new MySegment(Integer.parseInt(segkey[0]),Integer.parseInt(segkey[1]),Integer.parseInt(segkey[2]),Integer.parseInt(segkey[3]),Boolean.parseBoolean(segkey[4]),Integer.parseInt(segkey[5]),Byte.parseByte(segkey[6]));
+			if(seg.Check==Integer.parseInt(segkey[7]))
+			{
+				content[seg.SequenceNumber]=seg.Content;
+				acked=seg.SequenceNumber==acked+1?seg.SequenceNumber:acked;
+				while(acked<48&&content[acked+1]!=-1) acked++;
+				System.out.println("received segment "+seg.SequenceNumber);
+				receivedcache.setCharAt(seg.SequenceNumber,  (char)('0'+seg.Content));
+				label1.setText("received:"+receivedcache.toString());
+			}
+			else
+			{
+				error++;
+				label1.setText("received:"+receivedcache.toString());
+			}
+			MySegment segACK=new MySegment(socket.getLocalPort(),socket.getPort(),seg.SequenceNumber,acked,true,window,(byte)0);
+			send(segACK.toSend,osw);
+			System.out.println("sent ACK of "+segACK.AcknowledgementNumber);
+			if(acked==49)
+			{
+				send(segACK.toSend,osw);
+				send(segACK.toSend,osw);
+				send(segACK.toSend,osw);
+				send(segACK.toSend,osw);
+				finishTime=System.currentTimeMillis();
+				break;
+			}
+		}
+		long seconds=(finishTime-startTime)/1000;
+		label2.setText("Transfer speed: "+50/seconds+"Byte/s. Total error number: "+error);
+		socket.close();
+	}
+	
+}
+class ButtonHandler implements ActionListener {
+     public void actionPerformed(ActionEvent e) {
+    	 Client.window=Integer.parseInt(Client.windowSize.getSelectedItem());
+    	 Client.pauseflag=false;
+    	 Client.label2.setText("Current window size: "+Client.window);
+     }
+}
+