socket通信之客户端向服务端发送消息

socket通信属于TCP协议，是可靠的传输协议，内部进行了3次握手来确认信息传输的有效性，不丢失。
客户端socket向服务端serversocket发送消息
ClientSocketDemo 运行在A电脑，ServerSocketDemo 运行在B电脑，要保证通信成功，首先确保A,B在同一个网络下（A可以pingB，如通说明在同一个网络下）；B电脑的8080防火墙端口要打开（测试时，简单点可以把B的防火墙暂时关闭）

package lessons18;

import java.io.IOException;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;

public class ClientSocketDemo {

  public static void main(String[] args) throws UnknownHostException, IOException {
    // TODO Auto-generated method stub
    Socket socket = new Socket("192.168.3.2", 8080);
    PrintWriter out = new PrintWriter(socket.getOutputStream());
    out.println("aa");
    out.println("bb");
    out.println("cc");
    out.close();
    socket.close();
    
  }

}

package lessons18;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class ServerSocketDemo {

  public static void main(String[] args) throws IOException {
    // TODO Auto-generated method stub
    ServerSocket serverSocket = new ServerSocket(8080); //端口
    //socket对象封装客户端数据
    Socket socket = serverSocket.accept();
    //阻塞
    
    //从什么地方获取输入流 就是从什么地方读取数据
    InputStream inputStream = socket.getInputStream();
    BufferedReader reader = new BufferedReader(new InputStreamReader(
        inputStream));
    String str = null;
    while ((str = reader.readLine()) != null) {
       System.out.println(str);
    }
    reader.close();
    inputStream.close();
    socket.close();
    
  }

}