java socket大数据传输丢失问题及解决

public class Test {
    @org.junit.Test
    public void server() throws IOException {
        ServerSocket serverSocket = new ServerSocket(8080);
        while (true){
            Socket accept = serverSocket.accept();
            InputStream is = accept.getInputStream();
            byte[] bytes = new byte[5];
            int len = is.read(bytes);
            System.out.println(Arrays.toString(bytes));//发送端发送的数据只有两个字节，我们接收端设置为5个字节的字节数组，结果打印[1,2,0,0,0]，而不会在上一步阻塞
        }
    }

    @org.junit.Test
    public void client() throws IOException {
        Socket socket = new Socket("127.0.0.1",8080);
        OutputStream os = socket.getOutputStream();
        os.write(new byte[]{1,2});
    }
}

public static byte[] readData(InputStream is,int length) throws IOException {
        byte[] bytes = new byte[length];
        int index = 0;
        int len = 0;
        while(index < length){
            len = is.read(bytes,index,length - index);
            //每次读取完判断数据是否全部读取完毕
            if(len > 0){
                index += len;
            }else {
                break;
            }
        }
        return bytes;
    }