使用DataInputStream让服务器监听输入流

Question

我创建了一个java类TCPClient，它向TCPServer发送Message对象。我使用DataOutputStream和DataInputstream(这是我们被告知这样做的任务，为了将对象从客户机发送到服务器，我们必须使用它们两者)。这是我的TCPClient类

public class TCPClient {
public static final int PORT = 4000;
public static void main(String[] args){
    String hostname = "localhost";
    try(Socket client = new Socket(hostname,PORT);
        //BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));
        BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in))) {
        Message message;
        String input;
        String the_message;
        double random;
        int id;
        while(!(input = stdIn.readLine()).equalsIgnoreCase("end")){
            random =  Math.random()*100;
            message = new Message();
            the_message = input;
            id = (int)random;
            message.setId(id);
            message.setMessage(the_message);
            encode(message,client);
            //System.out.println(in.readLine());
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}
private static void encode(Message message, Socket client) {
    try(DataOutputStream out = new DataOutputStream(client.getOutputStream())){
        out.writeUTF(message.getMessage());
        out.writeInt(message.getId());
    } catch (IOException e) {
        e.printStackTrace();
    }
}}

TCPServer类

public class TCPServer {
public static final int PORT = 4000;
public static void main(String[] args) {
    try (ServerSocket ss = new ServerSocket(PORT);
         Socket cs = ss.accept();
         //PrintWriter out = new PrintWriter(cs.getOutputStream(), true);
    ) {
        Message message = decode(cs);
        System.out.print("Message received: " + message.getMessage() + " id: " + message.getId());

    } catch (IOException e) {
        e.printStackTrace();
    }
}
private static Message decode(Socket client){
    Message message = new Message();
    try(DataInputStream in = new DataInputStream(client.getInputStream())){
       message.setMessage(in.readUTF());
        message.setId(in.readInt());
        return message;
    } catch (IOException e) {
        System.err.print("Error happened while decoding object");
        return null;
    }
}}

我不想做的是，当我从客户端发送一个新的消息，服务器关闭。我希望服务器继续侦听消息。我该怎么做呢?

试过这样做

while(cs.getInputStream().available()==0){
            Message message = decode(cs);
            System.out.println("Message received = " + message.getMessage() + " id " + message.getId());
        }

但不工作

编辑:我不想建立一个多线程服务器托管几个客户端。我想要一个单一的服务器接收几个消息从一个唯一的客户端和关闭套接字每当客户端发送"结束"，我不知道如果这是可能的

Answer 1

您的客户端最多只发送一条消息，因为encode()通过关闭套接字输出流来关闭套接字。如果您希望客户端发送多个消息，请尝试这样做:

public class TCPClient {
    // ...
    public static void main(String[] args) {
        try (Socket client = new Socket(hostname, PORT);
             BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
             DataOutputStream out = new DataOutputStream(client.getOutputStream())) {
            // ...
            while (!(input = stdIn.readLine()).equalsIgnoreCase("end")) {
                // ...
                encode(message, out);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    private static void encode(Message message, DataOutputStream out) throws IOException {
        out.writeUTF(message.getMessage());
        out.writeInt(message.getId());
    }
}

服务器也接收到最多一条消息，因为decode()通过关闭其输入流来关闭套接字。应该这样做:

public class TCPServer {
    // ...
    public static void main(String[] args) {
        try (ServerSocket ss = new ServerSocket(PORT)) {
            // Accepts infinite clients.
            while (true) {
                try (Socket cs = ss.accept();
                     DataInputStream in = new DataInputStream(client.getInputStream())) {
                    boolean isClientOpen = true;
                    while (isClientOpen) {
                        try {
                            Message message = decode(in);
                            System.out.print("Message received: " + message.getMessage() + " id: " + message.getId());
                        } catch (IOException e) {
                            // The client may have closed the socket.
                            isClientOpen = false;
                        }
                    }
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    private static Message decode(DataInputStream in) throws IOException {
        Message message = new Message();
        message.setMessage(in.readUTF());
        message.setId(in.readInt());
        return message;
    }
}