JAVA多线程服务器套接字

Question

下面是接受客户端套接字连接并为每个连接分配线程的代码(JAVA)。

 ServerSocket m_ServerSocket = new ServerSocket();
 while (true) {
            java.util.Date today = Calendar.getInstance().getTime();
            System.out.println(today+" - Listening to new connections...");
           Socket clientSocket = m_ServerSocket.accept();
           ClientServiceThread cliThread = new ClientServiceThread( clientSocket);
           cliThread.start();
 }

假设连接了5个客户端，因此有5个线程在运行。

client 1: threadId 11
client 2: threadId 12
client 3 :threadId 13
client 4 :threadId 14
client 5 :threadId 15

假设其中一个客户端发送消息"kill-client1"，我希望终止客户端1的连接并杀死Id为11的线程，如下所示:

public void run() {
  try {
   BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
   PrintWriter out = new PrintWriter(new OutputStreamWriter(clientSocket.getOutputStream()));
   while (running) {
    String clientCommand = in .readLine();
    if (clientCommand.equalsIgnoreCase("Kill-client1")) {
       // end the connection for client 1 & kill it's corresponding thread 11
    }
   }
 } catch (Exception e) {
  e.printStackTrace();
 }
 }

如何实现这一目标?

Answer 1

跟踪所有客户端套接字和/或处理线程。

Map<Integer,Socket> clients=new HashMap<>();
 while (true) {
            java.util.Date today = Calendar.getInstance().getTime();
            System.out.println(today+" - Listening to new connections...");
           Socket clientSocket = m_ServerSocket.accept();
           clients.put(generateNewClientId(),clientSocket);
           ClientServiceThread cliThread = new ClientServiceThread( clientSocket);
           cliThread.start();
 }

然后如果你只做

{
    if (clientCommand.equalsIgnoreCase("Kill")) {
       Socket socket=clients.get(idToShutDown);// get required id somehow (from request??)
       socket.close();
    }
}

这将关闭给定的套接字，导致在处理线程时破坏in.readLine()，从而结束线程。

如果你跟踪线程，你可以设置"中断"标志并在while条件下探测它，这样你的处理线程将能够优雅地完成工作。

Answer 2

您可以通过使用线程id作为键

将Threads存储到线程安全映射(因为它将由多个线程并发访问)来做到这一点

// Map that will contain all my threads
Map<Long, ClientServiceThread> threads = new ConcurrentHashMap<>();
// Add to the constructor the instance of the class that manage the threads
ClientServiceThread cliThread = new ClientServiceThread(this, clientSocket);
// Add my new thread 
threads.put(cliThread.getId(), cliThread);
cliThread.start();

当一个击杀被发射时

String clientCommand = in.readLine().toLowerCase();
if (clientCommand.startsWith("kill")) {
    main.interrupt(Long.valueOf(clientCommand.substring(4).trim()));
}

然后在主类中你的方法看起来像:

public void interrupt(long threadId) {
    // Remove the thread from the map
    ClientServiceThread cliThread = threads.remove(threadId);
    if (cliThread != null) {
        // Interrupt the thread
        cliThread.interrupt();
    }
}

最后，您需要使您的类ClientServiceThread对中断敏感

try {
    ...
    while (!Thread.currentThread().isInterrupted()) {
        // My code here
    }
} finally {
    clientSocket.close();
}

Answer 3

终止循环:

   while (running) {
    String clientCommand = in .readLine();
    if (clientCommand.equalsIgnoreCase("Kill")) {
       running = false;
    }
   }

或:

   while (running) {
    String clientCommand = in .readLine();
    if (clientCommand.equalsIgnoreCase("Kill")) {
       break;
    }
   }

不要忘记关闭finally块中的套接字

Answer 4

要停止当前线程，请关闭套接字，并从run()方法返回:

if (clientCommand.equalsIgnoreCase("Kill")) {
   clientSocket.close();
   return;
}

编辑:

要关闭另一个线程，您可以，例如，

• 在线程之间共享一个线程安全的clientID-Thread表。当一个新客户端连接时，您将为该客户端启动的线程存储在这个映射
中
• 当Kill-client1命令进入时，您从映射中获得对应"client1"键的线程，并在该线程上调用ìnterrupt()。
• 中的每个线程(例如，client1线程)，在循环的每次迭代中，检查thread . currentthread (). isinterrupted()的值。如果为真，则关闭连接，从共享映射中删除线程，并从run()方法返回。

关键是你永远不会杀死另一个线程。您总是通过中断请求线程停止，线程检查其中断标志的值来决定何时以及如何停止。