Java多客户端socket服务器-饥饿

Question

考虑以下服务器:

public class TestServer {


public static void main(String[] args) {


    String ksName = "/some/path/keystore-server.jks";
    char ksPass[] = "password".toCharArray();
    char ctPass[] = "pswd".toCharArray();

    KeyStore ks;
    try {
        ks = KeyStore.getInstance("JKS");
        ks.load(new FileInputStream(ksName), ksPass);
        KeyManagerFactory kmf = 
        KeyManagerFactory.getInstance("SunX509");
        kmf.init(ks, ctPass);
        SSLContext sc = SSLContext.getInstance("TLS");
        sc.init(kmf.getKeyManagers(), null, null);
        SSLServerSocketFactory ssf = sc.getServerSocketFactory();
        SSLServerSocket s   = (SSLServerSocket) ssf.createServerSocket(SERVER_PORT);                

        while(true){                
            SSLSocket sslsocket = (SSLSocket) s.accept();
            System.out.println("New Client accepted");
            TestThread t = new TestThread(sslsocket);
            t.run();      
        }

    } catch (KeyStoreException | IOException | NoSuchAlgorithmException | CertificateException | UnrecoverableKeyException | KeyManagementException ex) {
        Logger.getLogger(TotalControlServer.class.getName()).log(Level.SEVERE, null, ex);
    }        
} 

}

上面是一个接受多个客户端的简单服务器:在接受新连接后，立即分派(dispatch)一个新线程(TestThread)以处理客户端传入请求。这是 TestThread 的代码:

public class TestThread implements Runnable {

SSLSocket sslsocket;

public TestThread(SSLSocket sslsocket) {
    this.sslsocket = sslsocket;
}

@Override
public void run() {

    ObjectInputStream is = null;
    ObjectOutputStream os = null;
    try {
        is = new ObjectInputStream(sslsocket.getInputStream());
        os = new ObjectOutputStream(sslsocket.getOutputStream());

        while(true){
            String p = (String) is.readObject();
            System.out.println("We got: " + p);

            os.writeObject(p.concat(p));
            os.flush();

        }//while         

    } catch (IOException ex) {
        Logger.getLogger(CmdLineService.class.getName()).log(Level.SEVERE, null, ex);
    } catch (ClassNotFoundException ex) {
        Logger.getLogger(CmdLineService.class.getName()).log(Level.SEVERE, null, ex);
    } finally {
        try {
            is.close();
            os.close();
            this.sslsocket.close();
        } catch (IOException ex) {
            Logger.getLogger(CmdLineService.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}//run

}

很简单，它只是无限循环地读取字符串并将其与自身的连接发回。

客户端也相当简单:

public class TestClient {


  public static void main(String[] args) {

    System.setProperty("javax.net.ssl.trustStore" , "/path/keystore-client.jks")  ;
    ObjectOutputStream os = null;
    ObjectInputStream is = null;
    SSLSocket sslsocket = null;

    try {
        SSLSocketFactory f = (SSLSocketFactory) SSLSocketFactory.getDefault();
        sslsocket = (SSLSocket) f.createSocket("localhost", SERVER_PORT);

        sslsocket.startHandshake();
        System.out.println("Authentication done");

        os = new ObjectOutputStream(sslsocket.getOutputStream());  
        is = new ObjectInputStream(sslsocket.getInputStream());


        BufferedReader b = new BufferedReader(new InputStreamReader(System.in)); 
        boolean exit = false;
        while(!exit){
            System.out.print("> ");
            String line = b.readLine();
            os.writeObject(line);
            os.flush();

            String s = (String) is.readObject();
            System.out.println(s);

        }//while

    } //main
    catch (IOException ex) {
        Logger.getLogger(TotalControlCmdClient.class.getName()).log(Level.SEVERE, null, ex);
    } catch (ClassNotFoundException ex) {
          Logger.getLogger(TestClient.class.getName()).log(Level.SEVERE, null, ex);
      } finally {

        try {
            is.close();  
            sslsocket.close();
        } catch (IOException ex) {
            Logger.getLogger(TestClient.class.getName()).log(Level.SEVERE, null, ex);
        }
    }       
}

只是无限循环地发送字符串和读取字符串。

这对于一个客户端来说效果很好。但是，如果我启动另一个客户端，它就无法连接!我似乎面临某种线程匮乏问题..

我该如何解决这个问题？

Answer 1

原因很简单:你永远不会启动第二个监听器线程:

   while(true){                
            SSLSocket sslsocket = (SSLSocket) s.accept();
            System.out.println("New Client accepted");
            TestThread t = new TestThread(sslsocket);
            t.run();      
        } 

调用run()不会启动线程，这是使用start()完成的。因此，主线程正在处理 run() 方法的内容，并且由于它很忙，因此您无法使用第二个客户端进行连接。

将t.run()更改为t.start，一切都会好起来的。