如何在Python中启动后台进程？(How to start a background process in Python?)

 这是一个示例 - 它不完整，但应该让您了解如何将输出多播到多个侦听客户端。 有更好的方法来做到这一点，但我写的类似于你似乎做插槽的方式。 它也缺乏许多地方的错误检查，我把它作为读者的练习。 此代码也已编写，因此可以在Java 1.6或更高版本上使用。 
 
 该代码使用Server对象中维护的已连接客户端列表。 当从一个客户端接收输入时，输出被多播到客户端列表中的每个客户端。 通过Client类中的write方法完成写入。 
 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.LinkedList;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class MulticastEchoServer {
    List<Client> clientList = new LinkedList<Client>();
    ExecutorService executor;

    int port = 40480;
    int max = 10;

    public MulticastEchoServer() {
        this.executor = Executors.newFixedThreadPool(max);
    }

    public void writeToAllClients(String string) throws IOException {
        // Multiple threads access this so it must be in synchronized block
        synchronized (this.clientList) {
            Iterator<Client> iter = this.clientList.iterator();
            while (iter.hasNext())
                iter.next().write(string);
        }
    }

    public void addClient(Client client) {
        // Multiple threads access this so it must be in synchronized block
        synchronized (this.clientList) {
            clientList.add(client);
        }
    }

    public void removeClient(Client client) {
        // Multiple threads access this so it must be in synchronized block
        synchronized (this.clientList) {
            clientList.remove(client);
        }
    }

    public void listen() {
        try {
            ServerSocket server = new ServerSocket(port);
            System.out.println("server started and listening for connections");

            while (true) {
                try {
                    Socket socket = server.accept();
                    System.out.print("connection accepted" + "\n");

                    Client newClient = new Client(this, socket);

                    this.addClient(newClient);
                    this.executor.execute(newClient);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        new MulticastEchoServer().listen();
    }

    private class Client implements Runnable {

        Socket socket;
        PrintWriter writer;
        BufferedReader reader;
        MulticastEchoServer server;

        public Client(MulticastEchoServer server, Socket socket) throws IOException {
            this.server = server;
            this.socket = socket;
            this.writer = new PrintWriter(this.socket.getOutputStream());
            this.reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        }

        synchronized public void write(String string) throws IOException {
            writer.write(string);
            writer.flush();
        }

        public void close() {
            this.writer.close();
            try {
                this.reader.close();
            } catch (IOException e) {
            }
            try {
                this.socket.close();
            } catch (IOException e) {
            }
        }

        @Override
        public void run() {
            System.out.println("Client Waiting");

            String inString = null;
            try {
                while ((inString = this.reader.readLine()) != null) {
                    this.server.writeToAllClients(inString + "\n");
                    System.out.println(inString);
                }
            } catch (IOException e1) {
            }

            server.removeClient(this);
            this.close();
            System.out.println("Client Closed");
        }
    }

}

This is an example - it is not complete but should give you an idea how you could multicast output to a number of listening clients. There are better ways to do this, but I wrote it similar to how you appeared to be doing the sockets. It also lacks error checking in many places and I have left that as an exercise for the reader. This code was also written so that it can be used on Java 1.6 or higher. 
 
The code uses a list of connected Clients maintained in the Server object. When input is received from one client, the output is multicast to each client in the Client list. Writing is done via a write method in the Client class.
 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.LinkedList;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class MulticastEchoServer {
    List<Client> clientList = new LinkedList<Client>();
    ExecutorService executor;

    int port = 40480;
    int max = 10;

    public MulticastEchoServer() {
        this.executor = Executors.newFixedThreadPool(max);
    }

    public void writeToAllClients(String string) throws IOException {
        // Multiple threads access this so it must be in synchronized block
        synchronized (this.clientList) {
            Iterator<Client> iter = this.clientList.iterator();
            while (iter.hasNext())
                iter.next().write(string);
        }
    }

    public void addClient(Client client) {
        // Multiple threads access this so it must be in synchronized block
        synchronized (this.clientList) {
            clientList.add(client);
        }
    }

    public void removeClient(Client client) {
        // Multiple threads access this so it must be in synchronized block
        synchronized (this.clientList) {
            clientList.remove(client);
        }
    }

    public void listen() {
        try {
            ServerSocket server = new ServerSocket(port);
            System.out.println("server started and listening for connections");

            while (true) {
                try {
                    Socket socket = server.accept();
                    System.out.print("connection accepted" + "\n");

                    Client newClient = new Client(this, socket);

                    this.addClient(newClient);
                    this.executor.execute(newClient);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        new MulticastEchoServer().listen();
    }

    private class Client implements Runnable {

        Socket socket;
        PrintWriter writer;
        BufferedReader reader;
        MulticastEchoServer server;

        public Client(MulticastEchoServer server, Socket socket) throws IOException {
            this.server = server;
            this.socket = socket;
            this.writer = new PrintWriter(this.socket.getOutputStream());
            this.reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        }

        synchronized public void write(String string) throws IOException {
            writer.write(string);
            writer.flush();
        }

        public void close() {
            this.writer.close();
            try {
                this.reader.close();
            } catch (IOException e) {
            }
            try {
                this.socket.close();
            } catch (IOException e) {
            }
        }

        @Override
        public void run() {
            System.out.println("Client Waiting");

            String inString = null;
            try {
                while ((inString = this.reader.readLine()) != null) {
                    this.server.writeToAllClients(inString + "\n");
                    System.out.println(inString);
                }
            } catch (IOException e1) {
            }

            server.removeClient(this);
            this.close();
            System.out.println("Client Closed");
        }
    }

}