Java 客户端服务器程序无限接受输入

Question

我是java套接字编程的新手，我正在制作一个客户端服务器程序。服务器是多线程的。当客户端与服务器的连接打开时。服务器向客户端发送一个文本块，如下所示：

connection is open with the server....
Welcome Please Chose one of the following Operations
Insert, Read, Update, Delete
Type Exit to terminate connection.

当我键入读取或退出或任何操作时，它工作正常，服务器响应。但是当我选择一个操作即插入时，就会出现问题——

public class Client1 {

public static void main(String[] args) throws IOException {

    Socket socket=null;

    try {

        System.out.println("sending connection request to host 127.0.0.1 at port 2000");
        socket = new Socket("127.0.0.1", 2000);

        System.out.println("connection is open with the server....");

        Scanner scn = new Scanner(System.in);

        DataOutputStream dos = new DataOutputStream(socket.getOutputStream());
        DataInputStream dis = new DataInputStream(socket.getInputStream());

        while (true) {

            System.out.println(dis.readUTF());
            String tosend = scn.nextLine();
            dos.writeUTF(tosend);

            // If client sends exit,close this connection
            // and then break from the while loop
            if (tosend.equals("Exit")) {
                System.out.println("Closing this connection : " + socket);
                socket.close();
                System.out.println("Connection closed");
                break;
            }

            String received = dis.readUTF();
            System.out.println(received);
        }
        // closing resources
        scn.close();
        dis.close();
        dos.close();
    }

        catch (Exception e ){
        System.out.println(e);
    } finally {

        try {
            if (socket != null) socket.close();
        } catch (Exception e){
            System.out.println(e);
        }
    }
}

public class ServerThread extends Thread{
Socket socket ;
DataInputStream dis;
DataOutputStream dos;

ServerThread(Socket socket,DataInputStream dis,DataOutputStream dos ){
    this.socket = socket;
    this.dis=dis;
    this.dos=dos;
}

@Override
public void run(){

    String received;
    String toreturn;
    String welcomeText = """
            Welcome Please Chose one of the following Operations
            Insert, Read, Update, Delete
            Type Exit to terminate connection.""";

    while (true){

    try {
        // Ask user what he wants
        dos.writeUTF(welcomeText);


        // receive the answer from client
        received = dis.readUTF();


        if(received.equals("Exit"))
        {
            System.out.println("Client " + this.socket + " sends exit...");
            System.out.println("Closing this connection.");
            this.socket.close();
            System.out.println("Connection closed");
            break;
        }

        // write on output stream based on the
        // answer from the client
        switch (received) {
// the problem starts here if I chose insert and wanna print what the user typed, it takes  
//input infinitely from the user
            case "Insert":
                toreturn = "Inserting new info...";
                dos.writeUTF(toreturn);
                String out = dis.readUTF();
                dos.writeUTF("Accepted");
                dos.writeUTF(out);
                break;

            case "Read":
                toreturn = "Reading User Info...";
                dos.writeUTF(toreturn);
                break;

            case "Update":
                toreturn = "Updating User Info...";
                dos.writeUTF(toreturn);
                break;

            case "Delete":
                toreturn = "Deleting User Info";
                dos.writeUTF(toreturn);
                break;


            default:
                dos.writeUTF("Unknown User");

                break;
        }

    } catch ( IOException e) {
        e.printStackTrace();
    }
    }

    try
    {
        // closing resources
        this.dis.close();
        this.dos.close();

    }catch(IOException e){
        e.printStackTrace();
    }
    }
}

我不知道这个循环是如何发生的，特别是因为服务器在选择操作时正确接受输入，但是当选择插入操作时，它只是无限地接受输入，有人能帮忙吗，如果这个问题仍然存在，我无法实现任何操作。

Answer 1

我认为这是您的客户机，在while循环中，尝试从服务器中删除第二次读取，这是因为您曾经读取了服务器发送的所有内容，当循环再次启动时，您希望从服务器中读取，但没有什么可读取的内容，并变得空闲。