Question

我有服务器和客户端。我的问题是，当客户端写入消息时，服务器没有收到消息。服务器代码

public class BankServer {

    private int port;

    private BufferedReader reader = null; 
    private PrintWriter writer = null;

    public BankServer(int port)
    {
        this.port = port;
    }

    public void startServer() {
        print("Contact server at: " + getServerAddress() + ": port: " + port);

        while(true) {
            try {
                ServerSocket ss = new ServerSocket(port);
                Socket client = ss.accept();

                if(client != null) {
                    print("Client connected");
                }

                reader = new BufferedReader(new InputStreamReader(client.getInputStream()));
                writer = new PrintWriter(client.getOutputStream(), true);

                String msg = null;

                print("Server waiting for input");

                while((msg = reader.readLine()) != null) {
                    print("Printer: " + msg);
                    writer.write(msg);
                }

                client.close();
                ss.close();
                closeStreams();

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

    private void closeStreams() {
        if(reader != null) { 
            try {
                reader.close();
            } catch (IOException e) {
                e.printStackTrace();
            } }

        if(writer != null) {
            writer.close();
        }       
    }

    private String getServerAddress() {

        InetAddress inetAdr = null;

        try {
            inetAdr = InetAddress.getLocalHost();
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }

        String host = inetAdr.getHostAddress();

        return host;
    }

    public void print(String msg) {
        System.out.println(msg);
    }

    public static void main(String[] args) {        
        new BankServer(2222).startServer();
    }

}

我有这段代码，服务器等待输入：

ServerSocket ss = new ServerSocket(port);
        Socket client = ss.accept();

        if(client != null) {
            print("Client connected");
}

从这段代码中，我可以看到建立了连接。但是当客户端发送消息时，它们不会被服务器打印

以下是客户端代码：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.Scanner;

public class BankClient {

    private PrintWriter writer = null;
    private BufferedReader reader = null;
    private Socket socket;

    private int port;
    private String adr;

    public BankClient(String address, int port) 
    {
        adr = address;
        this.port = port;

        try {
            socket = new Socket(adr, this.port);
            reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            writer = new PrintWriter(socket.getOutputStream());


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

    public void writeMsg(String msg) {

        try {
            while((msg = reader.readLine()) != null) {
                writer.print("From client: " + msg);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {

        BankClient client = new BankClient("127.0.0.1", 2222);
        Scanner scanner = new Scanner(System.in);

        System.out.println("Waiting for input");

        while(true) {
            String msg = scanner.nextLine();
            client.writeMsg(msg);

            if(msg.equals("quit")) { 
                System.out.println("Bye");
                break; 
            }                       
        }

        scanner.close();
    }
}

这是我第一次使用流，而且我对编程也很陌生。我在 stackoverflow 和 google 上找到了很多帮助，但我无法理解这一点。感谢您提供的任何帮助

Answer 1

替换：

public void writeMsg(String msg) {

        try {
            while((msg = reader.readLine()) != null) {
                writer.print("From client: " + msg);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

通过：

public void writeMsg(String msg) {
        try {
            DataOutputStream outToServer = new DataOutputStream(socket.getOutputStream());
            outToServer.writeBytes("From client: " + msg + "\n");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

客户端：

服务器端：

Answer 2

更改 writer.print("From client: " + msg); 至 writer.println("From client: " + msg); 并删除客户端的while((msg = reader.readLine()) != null)。

编辑：你必须添加writer.flush();。这对我有用。

EDIT2：完整的解决方案。在此处更改BankClient：

public void writeMsg(String msg) { writer.println("From client: " + msg); writer.flush(); }

服务器没有从客户端接收输入

2 个答案: