如何在客户端之间持续发送消息？

Question

我有一个简单的 client/server 应用程序，它将 2 个客户端分组并使它们相互通信，如果第三个客户端连接，它将无法与其他 2 个客户端通信，但它会创建另一个组2个客户端等等......但是当我从客户端发送消息时出现问题它不会立即将其发送到另一个客户端而是等待第一个客户端输入并且它还等待第二个客户端输入只有当两个客户端都输入了输入时，它才会将它们发送给彼此。非常感谢任何帮助。

服务器：

public class ChatServer {

    Socket previousSocket = null;
    
    public static void main(String[] args) throws Exception {
        ServerSocket serverSocket = new ServerSocket(9001);
        System.out.println("The chat server is running.");
        Socket previousSocket = null;
        while (true) {
            Socket newSocket = serverSocket.accept();
            
            /**
             * if (previousSocket == null) occurs if only 1 client is connected and its being set as a previousSocket
             * and we wait for a second client to connect so meanwhile nothing happens
             * 
             * if second clients joins in we can start communicating in groups of 2
             */
            
            if (previousSocket == null) { 
                previousSocket = newSocket;
            } else {
                new Handler(previousSocket, newSocket).start();
                new Handler(newSocket, previousSocket).start();
                previousSocket = null;
            }
        }
    }

    
    private static class Handler extends Thread {
        private String name;
        private Socket socket;
        private Socket peerSocket;
        private DataInputStream in;
        private DataOutputStream out;

        public Handler(Socket socket, Socket peerSocket) {
            this.socket = socket;
            this.peerSocket = peerSocket;
        }

        public void run() {
            try {
                while (true) {
                in = new DataInputStream(socket.getInputStream());
                out = new DataOutputStream(peerSocket.getOutputStream());
                
                
                

                    try {
                        String input = in.readUTF();
                        

                            out.writeUTF(input);
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                   
                }
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            
        }
    }
}

客户：

public class ChatClient {

    public static void main(String[] args) throws UnknownHostException, IOException {
        new ChatClient();
    }
    
    public ChatClient() throws UnknownHostException, IOException  {
        Socket socket = new Socket("127.0.0.1", 9001);
        
        System.out.println("You can start typing:");
        
        while(true) {
            
            
            Scanner scanner = new Scanner(System.in);
            
            Thread input = new Thread() {
                @Override
                public void run() {
                    while(true) {
                        try {
                            DataInputStream inputStream = new DataInputStream(socket.getInputStream());
                            
                            while(scanner.hasNextLine()) {
                                String message = scanner.nextLine();
                                
                                System.out.println(message);
                                
                                //reading messages from server
                                String received = inputStream.readUTF();
                                System.out.println(received);
                            }
                        } catch (IOException e) {
                            
                            e.printStackTrace();
                        }
                    }
                }
            };
            input.start();
            
            Thread output = new Thread() {
                public void run() {
                    try {
                        DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
                        while(scanner.hasNextLine()) {
                            String message = scanner.nextLine();
                            
                            if(message.equalsIgnoreCase("quit")) {
                                socket.close();
                                break;
                            }
                            
                            outputStream.writeUTF(message);
                        }
                    } catch (IOException e) {
                        
                        e.printStackTrace();
                    }
                    
                    
                };
            };
            output.start();

            
        }
    }
}

Answer 1

您需要将客户端中的输入流和输出流分离到两个单独的线程中。问题是您的客户端在您读取输入之前正在等待来自扫描仪的输入。 Scanner 是一个阻塞调用，所以它需要自己的线程。

此外，您应该将循环中数据流的创建移至构造函数...这将提高您的效率。

Answer 2

删除顶级 while 循环并删除 scanner.nextLine() 从服务器读取时，在客户端。
我已经在下面更新了您的客户端代码，这应该可以正常工作。

public class ChatClient {

    public static void main(String[] args) throws UnknownHostException, IOException {
        new ChatClient();
    }
    
    public ChatClient() throws UnknownHostException, IOException  {
        Socket socket = new Socket("127.0.0.1", 9001);
        
        System.out.println("You can start typing:");
            
            
            Scanner scanner = new Scanner(System.in);
            System.out.println("got it");
            Thread input = new Thread() {
                @Override
                public void run() {
                    while(true) {
                        try {
                            DataInputStream inputStream = new DataInputStream(socket.getInputStream());
                            
                            while(true) {
                                //String message = scanner.nextLine();
                                
                                //System.out.println(message);
                                
                                //reading messages from server
                                String received = inputStream.readUTF();
                                System.out.println(received);
                            }
                        } catch (IOException e) {
                            
                            e.printStackTrace();
                        }
                    }
                }
            };
            input.start();
            
            Thread output = new Thread() {
                public void run() {
                    try {
                        DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
                        while(scanner.hasNextLine()) {
                            String message = scanner.nextLine();
                            
                            if(message.equalsIgnoreCase("quit")) {
                                socket.close();
                                break;
                            }
                            
                            outputStream.writeUTF(message);
                        }
                    } catch (IOException e) {
                        
                        e.printStackTrace();
                    }
                    
                    
                };
            };
            output.start();
    }
}

如何在客户端之间持续发送消息？

How to continuously send messages between clients?

java

sockets

networking

tcp

client-server