实现客户端和服务器的一问一答，tcp比较可靠，demo中体现在先启客户端再启服务器会报refuse错误等。

服务器端代码：

package socket_demo1;

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

public class SocketServer {
    public static void main(String[] args) throws IOException {
        //设置服务器端口
        ServerSocket ss = new ServerSocket(10086);
        //阻塞，以接收客户端数据
        Socket socket = ss.accept();
        //获取输入流
        InputStream is = socket.getInputStream();
        //通过InputStreamReader设置编码
        InputStreamReader isr = new InputStreamReader(is, "utf-8");

        int i = 0;
        StringBuffer sb = new StringBuffer();
        //当读数据读取到最后，返回-1
        while ((i = isr.read()) != -1) {
            System.out.print((char) i);
            sb.append((char) i);
        }
        //shutdown输入流，可理解这一步为切换IO流
        socket.shutdownInput();
        //获取输入流
        OutputStream os = socket.getOutputStream();
        if ("chen".equals(sb.toString())) {
            os.write("牛逼！".getBytes());
        } else {
            os.write("what?".getBytes());
        }
        System.out.println();
        
        socket.shutdownOutput();
        isr.close();
        os.close();
        is.close();
    }
}

客户端代码：

package socket_demo1;

import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.Socket;
import java.util.Scanner;

public class ClientSocket {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        // 不是多线程 他也没有 accept的监听

        //设置请求地址和端口
        Socket socket = new Socket("127.0.0.1", 10086);
        OutputStream os = socket.getOutputStream();
        System.out.println("输入消息：");
        String msg = sc.next();
        os.write(msg.getBytes());

        socket.shutdownOutput();

        InputStream is = socket.getInputStream();
        InputStreamReader isr = new InputStreamReader(is, "utf-8");

        int i = 0;
        while ((i = isr.read()) != -1) {
            System.out.print((char) i);
        }
        System.out.println();
        socket.shutdownInput();

        isr.close();
        os.close();
        is.close();
    }
}

先启动服务器，再启动客户端，在客户端的控制台输入“chen”,或者其他消息，服务器可返回不同的消息。如：

输入消息：
chen
牛逼！

但是先启动客户端再启动服务器，就会报错：

Exception in thread "main" java.net.ConnectException: Connection refused: connect
    at java.net.DualStackPlainSocketImpl.connect0(Native Method)
    at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:589)
    at java.net.Socket.connect(Socket.java:538)
    at java.net.Socket.<init>(Socket.java:434)
    at java.net.Socket.<init>(Socket.java:211)
    at socket_demo1.ClientSocket.main(ClientSocket.java:16)