public class SocketClient {
  private static final Integer SIZE = 1024;
  private static final ThreadPoolExecutor socketPoll = new ThreadPoolExecutor(50, 50,
                                                                               365L,
                                                                               TimeUnit.DAYS,
                                                                               new LinkedBlockingQueue<>(400));
  @Test
  public void test() throws InterruptedException {
    // 模擬客戶端同時(shí)向服務(wù)端發(fā)送 6 條消息
    for (int i = 0; i < 6; i++) {
      socketPoll.submit(() -> {
        send("localhost", 7007, "nihao");
      });
    }
    Thread.sleep(1000000000);
  }
  /**
   * 發(fā)送tcp
   *
   * @param domainName 域名
   * @param port       端口
   * @param content    發(fā)送內(nèi)容
   */
  public static String send(String domainName, int port, String content) {
    log.info("客戶端開(kāi)始運(yùn)行");
    Socket socket = null;
    OutputStream outputStream = null;
    InputStreamReader isr = null;
    BufferedReader br = null;
    InputStream is = null;
    StringBuffer response = null;
    try {
      if (StringUtils.isBlank(domainName)) {
        return null;
      }
      // 無(wú)參構(gòu)造器初始化 Socket，默認(rèn)底層協(xié)議是 TCP
      socket = new Socket();
      socket.setReuseAddress(true);
      // 客戶端準(zhǔn)備連接服務(wù)端，設(shè)置超時(shí)時(shí)間 10 秒
      socket.connect(new InetSocketAddress(domainName, port), 10000);
      log.info("TCPClient 成功和服務(wù)端建立連接");
      // 準(zhǔn)備發(fā)送消息給服務(wù)端
      outputStream = socket.getOutputStream();
      // 設(shè)置 UTF 編碼，防止亂碼
      byte[] bytes = content.getBytes(Charset.forName("UTF-8"));
      // 輸出字節(jié)碼
      segmentWrite(bytes, outputStream);
      // 關(guān)閉輸出
      socket.shutdownOutput();
      log.info("TCPClient 發(fā)送內(nèi)容為 {}",content);
      // 等待服務(wù)端的返回
      socket.setSoTimeout(50000);//50秒還沒(méi)有得到數(shù)據(jù)，直接斷開(kāi)連接
      // 得到服務(wù)端的返回流
      is = socket.getInputStream();
      isr = new InputStreamReader(is);
      br = new BufferedReader(isr);
      // 從流中讀取返回值
      response = segmentRead(br);
      // 關(guān)閉輸入流
      socket.shutdownInput();
      //關(guān)閉各種流和套接字
      close(socket, outputStream, isr, br, is);
      log.info("TCPClient 接受到服務(wù)端返回的內(nèi)容為 {}",response);
      return response.toString();
    } catch (ConnectException e) {
      log.error("TCPClient-send socket連接失敗", e);
      throw new RuntimeException("socket連接失敗");
    } catch (Exception e) {
      log.error("TCPClient-send unkown errror", e);
      throw new RuntimeException("socket連接失敗");
    } finally {
      try {
        close(socket, outputStream, isr, br, is);
      } catch (Exception e) {
        // do nothing
      }
    }
  }
  /**
   * 關(guān)閉各種流
   *
   * @param socket
   * @param outputStream
   * @param isr
   * @param br
   * @param is
   * @throws IOException
   */
  public static void close(Socket socket, OutputStream outputStream, InputStreamReader isr,
                           BufferedReader br, InputStream is) throws IOException {
    if (null != socket && !socket.isClosed()) {
      try {
        socket.shutdownOutput();
      } catch (Exception e) {
      }
      try {
        socket.shutdownInput();
      } catch (Exception e) {
      }
      try {
        socket.close();
      } catch (Exception e) {
      }
    }
    if (null != outputStream) {
      outputStream.close();
    }
    if (null != br) {
      br.close();
    }
    if (null != isr) {
      isr.close();
    }
    if (null != is) {
      is.close();
    }
  }
  /**
   * 分段讀
   *
   * @param br
   * @throws IOException
   */
  public static StringBuffer segmentRead(BufferedReader br) throws IOException {
    StringBuffer sb = new StringBuffer();
    String line;
    while ((line = br.readLine()) != null) {
      sb.append(line);
    }
    return sb;
  }
  /**
   * 分段寫(xiě)
   *
   * @param bytes
   * @param outputStream
   * @throws IOException
   */
  public static void segmentWrite(byte[] bytes, OutputStream outputStream) throws IOException {
    int length = bytes.length;
    int start, end = 0;
    for (int i = 0; end != bytes.length; i++) {
      start = i == 0 ? 0 : i * SIZE;
      end = length > SIZE ? start + SIZE : bytes.length;
      length -= SIZE;
      outputStream.write(bytes, start, end - start);
      outputStream.flush();
    }
  }
}

public class SocketServiceStart {
  /**
   * 服務(wù)端的線程池，兩個(gè)作用
   * 1：讓服務(wù)端的任務(wù)可以異步執(zhí)行
   * 2：管理可同時(shí)處理的服務(wù)端的請(qǐng)求數(shù)
   */
  private static final ThreadPoolExecutor collectPoll = new ThreadPoolExecutor(4, 4,
                                                                               365L,
                                                                               TimeUnit.DAYS,
                                                                               new LinkedBlockingQueue<>(
                                                                                   1));
  @Test
  public void test(){
    start();
  }
  /**
   * 啟動(dòng)服務(wù)端
   */
  public static final void start() {
    log.info("SocketServiceStart 服務(wù)端開(kāi)始啟動(dòng)");
    try {
      // backlog  serviceSocket處理阻塞時(shí)，客戶端最大的可創(chuàng)建連接數(shù)，超過(guò)客戶端連接不上
      // 當(dāng)線程池能力處理滿了之后，我們希望盡量阻塞客戶端的連接
//      ServerSocket serverSocket = new ServerSocket(7007,1,null);
      // 初始化服務(wù)端
      ServerSocket serverSocket = new ServerSocket();
      serverSocket.setReuseAddress(true);
//      serverSocket.bind(new InetSocketAddress(InetAddress.getLocalHost().getHostAddress(), 80));
      serverSocket.bind(new InetSocketAddress("localhost", 7007));
      log.info("SocketServiceStart 服務(wù)端啟動(dòng)成功");
      // 自旋，讓客戶端一直在取客戶端的請(qǐng)求，如果客戶端暫時(shí)沒(méi)有請(qǐng)求，會(huì)一直阻塞
      while (true) {
        // 接受客戶端的請(qǐng)求
        Socket socket = serverSocket.accept();
        // 如果隊(duì)列中有數(shù)據(jù)了，說(shuō)明服務(wù)端已經(jīng)到了并發(fā)處理的極限了，此時(shí)需要返回客戶端有意義的信息
        if (collectPoll.getQueue().size() >= 1) {
          log.info("SocketServiceStart 服務(wù)端處理能力到頂，需要控制客戶端的請(qǐng)求");
          //返回處理結(jié)果給客戶端
          rejectRequest(socket);
          continue;
        }
        try {
          // 異步處理客戶端提交上來(lái)的任務(wù)
          collectPoll.submit(new SocketService(socket));
        } catch (Exception e) {
          socket.close();
        }
      }
    } catch (Exception e) {
      log.error("SocketServiceStart - start error", e);
      throw new RuntimeException(e);
    } catch (Throwable e) {
      log.error("SocketServiceStart - start error", e);
      throw new RuntimeException(e);
    }
  }
	// 返回特定的錯(cuò)誤碼給客戶端
  public static void rejectRequest(Socket socket) throws IOException {
    OutputStream outputStream = null;
    try{
      outputStream = socket.getOutputStream();
      byte[] bytes = "服務(wù)器太忙了，請(qǐng)稍后重試~".getBytes(Charset.forName("UTF-8"));
      SocketClient.segmentWrite(bytes, outputStream);
      socket.shutdownOutput();
    }finally {
      //關(guān)閉流
      SocketClient.close(socket,outputStream,null,null,null);
    }
  }
}

public class SocketService implements Runnable {
  private Socket socket;
  public SocketService() {
  }
  public SocketService(Socket socket) {
    this.socket = socket;
  }
  @Override
  public void run() {
    log.info("SocketService 服務(wù)端任務(wù)開(kāi)始執(zhí)行");
    OutputStream outputStream = null;
    InputStream is = null;
    InputStreamReader isr = null;
    BufferedReader br = null;
    try {
      //接受消息
      socket.setSoTimeout(10000);// 10秒還沒(méi)有得到數(shù)據(jù)，直接斷開(kāi)連接
      is = socket.getInputStream();
      isr = new InputStreamReader(is,"UTF-8");
      br = new BufferedReader(isr);
      StringBuffer sb = SocketClient.segmentRead(br);
      socket.shutdownInput();
      log.info("SocketService accept info is {}", sb.toString());
      //服務(wù)端處理 模擬服務(wù)端處理耗時(shí)
      Thread.sleep(2000);
      String response  = sb.toString();
      //返回處理結(jié)果給客戶端
      outputStream = socket.getOutputStream();
      byte[] bytes = response.getBytes(Charset.forName("UTF-8"));
      SocketClient.segmentWrite(bytes, outputStream);
      socket.shutdownOutput();
      //關(guān)閉流
      SocketClient.close(socket,outputStream,isr,br,is);
      log.info("SocketService 服務(wù)端任務(wù)執(zhí)行完成");
    } catch (IOException e) {
      log.error("SocketService IOException", e);
    } catch (Exception e) {
      log.error("SocketService Exception", e);
    } finally {
      try {
        SocketClient.close(socket,outputStream,isr,br,is);
      } catch (IOException e) {
        log.error("SocketService IOException", e);
      }
    }
  }
}