ByteArrayOutputStream 对byte类型数据进行写入的类 ，自动扩容，相当于一个中间缓冲层，将类写入到文件等其他outputStream。它是对字节进行操作，属于内存操作流

 

import java.io.ByteArrayOutputStream;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.net.Socket;public class SocketUtils {private final static String ip = "127.0.0.1";private final static int port = 12345;private final static int timeout = 5000;public static void sendMsg() {Socket clientSocket = null;try {clientSocket = new Socket();//连接上后，生成SocketclientSocket.connect(new InetSocketAddress(ip, port),timeout);ByteArrayOutputStream outputStream = new ByteArrayOutputStream();outputStream.write(intToBytesToLH4(4090));outputStream.write(intToBytesToLH2(2));outputStream.write(intToBytesToLH2(2));outputStream.write(intToBytesToLH4(1));byte[] b = new byte[16];System.arraycopy("".getBytes(), 0, b, 0, "".getBytes().length);b["".getBytes().length] = 0;outputStream.write(b);socket关联的输出流对象OutputStream outputStream1 = clientSocket.getOutputStream();//将缓冲区的数据全部获取出来，返回字节数组byte[] c = outputStream.toByteArray();//通过输出流，写入数据到数据通道outputStream1.write(c);//清空缓存并输出流outputStream1.flush();//关闭流对象outputStream1.close();} catch (Exception e) {e.printStackTrace();} finally {// 关闭客户端Socket连接try {clientSocket.close();} catch (Exception e) {e.printStackTrace();}}}// 将int转为低字节在前，高字节在后的byte数组private static byte[] intToBytesToLH2(int n) {byte[] b = new byte[2];b[0] = (byte) (n & 0xff);b[1] = (byte) (n >> 8 & 0xff);return b;}private static byte[] intToBytesToLH4(int n) {byte[] b = new byte[4];b[0] = (byte) (n & 0xff);b[1] = (byte) (n >> 8 & 0xff);b[2] = (byte) (n >> 16 & 0xff);b[3] = (byte) (n >> 24 & 0xff);return b;}}