程序代码：

    public void run() {
        try {
            // get out and in stream
            DataOutputStream dout = new DataOutputStream(s.getOutputStream());
            DataInputStream din = new DataInputStream(s.getInputStream());
            dout.writeUTF("{FileList}" + fileList);
            FileInputStream fis;
            DataInputStream dataIn;
            int length = 0;
            ta.append(din.readUTF() + "\n");
            state = "send";
            
            // send file one by one
            for(File f : fileList) {                
                dout.writeUTF("{FileBegin}" + f);
                fis = new FileInputStream(f);
                dataIn = new DataInputStream(fis);
                byte[] buffer = new byte[1024];// 定义一byte类型的缓冲区

                // send buffer length once
                ta.append("File:  " + f + " send begin!\n");
                while ((length = dataIn.read(buffer)) != -1) {
                    dout.write(buffer, 0, length);
                }
                ta.append("File:  " + f + " send end!\n");
                
                dout.flush();
                fis.close();
                dataIn.close();
            }
            din.close();
            dout.close();
            s.close();

            state = "rest";
        }
        catch(Exception exc) {
            exc.printStackTrace();
        }        
    }

程序代码：

    public void receiveFile() {
        state="receive";
        
        try {
            dout.writeUTF("{ReceiveFiles}");

            // receive each file through one new socket
            for(int i=0; i<list.length; i++) {
                // read file name
                String str = din.readUTF();
                int j=str.lastIndexOf("\\");
                
                // create file output
                File f = new File(path.getPath() + "\\" + str.substring(j+1));
                if(!f.exists())
                    f.createNewFile();
                FileOutputStream fos = new FileOutputStream(f);
                int length=0;
                byte[] buffer = new byte[1024];
                
                // read file buffer and write it into file f
                ta.append("File:  " + f + " receive begin!\n");
                while ((length = din.read(buffer)) != -1) {
                    fos.write(buffer, 0, length);
                }
                
                fos.close();
                ta.append("File:  " + f + " receive end!\n");
            }
            din.close();
            socket.close();
        }
        catch(Exception e) {
            e.printStackTrace();
        }
        
        state="rest";
    }