tcp，第一个例子，客户端，服务端

package cd.itcast.xieyi;

import java.io.IOException;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;

/*
 * tcp协议的socket
 *         socket(客户端),tcp的客户端一旦启动马上要与服务端建立连接。
 *         ServerSocket(服务端类)
 * 
 * tcp客户端的使用步骤：
 */
public class Demo2Client {
    public static void main(String[] args) throws UnknownHostException, IOException {
        //建立tcp的客户端服务
        Socket socket = new Socket(InetAddress.getLocalHost(), 9090);
        //获得输出流对象
        OutputStream outputStream = socket.getOutputStream();
        //利用输出流写出数据
        outputStream.write("甘兴瑞您好！！".getBytes());
        //关闭资源
        socket.close();
    }
}

package cd.itcast.xieyi;

import java.io.IOException;
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class Demo2Server {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(9090);
        //接受客户端连接,有等待特性，返回socket对象
        Socket socket = serverSocket.accept();
        //获得输入流
        InputStream inputStream = socket.getInputStream();
        //读入数据
        byte[] buf = new byte[1024];
        int length=0;
        length = inputStream.read(buf);
        System.out.println("服务端接受到的数据："+new String(buf,0,length));
        //关闭资源
        socket.close();
    }
}