参考资料： TCP的Socket编程

左图：BIO Socket的单线程模式 右图：BIO Socket的多线程模式

public class SocketClient
{public static void main(String args[]) throws Exception{Socket socket = new Socket("192.168.100.236", 2221);System.out.println("socket created");// send requestOutputStream os = socket.getOutputStream();PrintWriter pw = new PrintWriter(os);System.out.println("send: hello");pw.write("hello");pw.flush();socket.shutdownOutput();// receview responseInputStream is = socket.getInputStream();InputStreamReader isr = new InputStreamReader(is);BufferedReader br = new BufferedReader(isr);String line = null;System.out.println("received: ");while ((line = br.readLine()) != null) {System.out.println(line);}socket.shutdownInput();//close resourcebr.close();pw.close();os.close();socket.close();}
}//服务器端（解决单客户端连接）
public class SocketServer
{public static void main(String args[]) throws Exception{       ServerSocket serverSocket = new ServerSocket(2221);System.out.println("server socket created");System.out.println("***");Socket socket = serverSocket.accept();//receives requestInputStream is = socket.getInputStream();InputStreamReader isr = new InputStreamReader(is);BufferedReader br = new BufferedReader(isr);String line = null;System.out.println("received: ");while ((line = br.readLine()) != null) {System.out.println(line);}socket.shutdownInput();//send responseOutputStream os = socket.getOutputStream();PrintWriter pw  = new PrintWriter(os);System.out.println("send: server received");pw.write("server received");pw.flush();socket.shutdownOutput();//close resourcepw.close();         br.close();isr.close();is.close();socket.close();serverSocket.close();}
}

//多线程服务端（解决多客户端连接）
public class SocketServer
{public static void main(String args[]) throws Exception{       ServerSocket serverSocket = new ServerSocket(2221);System.out.println("server socket created");while (true) //循环监听，等待客户端的连接{System.out.println("***");Socket socket = serverSocket.accept();ServerHandler serverHandler = new ServerHandler(socket);serverHandler.start();}}class ServerHandler extends Thread
{private final Logger logger = LoggerFactory.getLogger(getClass());//与本线程相关的Socketprivate Socket socket = null;public ServerHandler(Socket socket){this.socket = socket;}//线程执行的操作public void run(){InputStream is = null;InputStreamReader isr = null;BufferedReader br = null;OutputStream os = null;PrintWriter pw = null;try{//receives requestis = socket.getInputStream();isr = new InputStreamReader(is);br = new BufferedReader(isr);String line = null;System.out.println("received: ");while ((line = br.readLine()) != null) {System.out.println(line);}socket.shutdownInput();//send responseos = socket.getOutputStream();pw  = new PrintWriter(os);System.out.println("send: server received");pw.write("server received");pw.flush();socket.shutdownOutput();  }catch(Exception ex){logger.error(ex.getMessage());ex.printStackTrace(System.out);          }finally{//close resourcetry{pw.close();            br.close();isr.close();is.close();socket.close();}catch(Exception ex){ex.printStackTrace(System.out);}}}
}
}