java - 我如何从java中的服务器TCP获得回复

Question

我的代码只是做一个简单的任务，从客户端的控制台发送文本到服务器并接收回复。但是我的代码不起作用。我一直向服务器发送文本，但没有回复发回。我做了几个例子，加上客户给的 2 个数字。我以同样的方式执行此操作，但我无法弄清楚问题出在哪里。

服务器:

public class Server {
    public static void main(String[] args) {
        try {
            ServerSocket server = new ServerSocket(8);
            Socket client = server.accept();
            BufferedReader inFromClient = new BufferedReader(new InputStreamReader(client.getInputStream()));
            BufferedWriter outToClient = new BufferedWriter(new OutputStreamWriter(client.getOutputStream()));
            String in = inFromClient.readLine(),out;
            while(in!=null){
                out = in+" from server";
                outToClient.write(out);
                outToClient.newLine();
                outToClient.flush();
            }
            inFromClient.close();
            outToClient.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
}

客户:

public class Client {
    public static void main(String[] args) {
        try {
            Socket client = new Socket("localhost", 8);
            System.out.println("Connected to server");
            BufferedReader inFromServer = new BufferedReader(new InputStreamReader(client.getInputStream()));
            BufferedWriter outToServer = new BufferedWriter(new OutputStreamWriter(client.getOutputStream()));
            Scanner input = new Scanner(System.in);
            String strClient,strServer;
            while(true){
                System.out.print("Client: ");
                strClient = input.nextLine();
                outToServer.write(strClient);
                strServer = inFromServer.readLine();
                System.out.print("Server: ");
                System.out.println(strServer);
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
}

Answer 1

你的代码有几个问题:

1. 您的服务器期望读取一行，而您只写了没有换行符的文本:

读取服务器中的一行:inFromClient.readLine()

在客户端写入不带换行符的文本:outToServer.write(strClient);将其更改为 outToServer.write(strClient + "\n");

---

1. 您不刷新客户的作者。在 outToServer.write(...);
行之后添加 outToServer.flush();

---

1. 您只读取服务器中的 1 行并且不再在循环中读取。

---

编辑:为了方便起见，我将在此处发布更正后的代码:(我已经尝试过了，效果非常好)

客户:

public class Client {
    public static void main(String[] args) {
        try (Socket client = new Socket("localhost", 8);
            BufferedReader inFromServer = new BufferedReader(new InputStreamReader(client.getInputStream()));
            BufferedWriter outToServer = new BufferedWriter(new OutputStreamWriter(client.getOutputStream()));
            Scanner input = new Scanner(System.in)) {

            System.out.println("Connected to server");
            String strClient,strServer;

            while(true){
                System.out.print("Client: ");
                strClient = input.nextLine();
                outToServer.write(strClient);
                outToServer.newLine();
                outToServer.flush();
                strServer = inFromServer.readLine();
                System.out.println("Server: " + strServer);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

服务器:

public class Server {
    public static void main(String[] args) {
        try (ServerSocket server = new ServerSocket(8);
            Socket client = server.accept();
            BufferedReader inFromClient = new BufferedReader(new InputStreamReader(client.getInputStream()));
            BufferedWriter outToClient = new BufferedWriter(new OutputStreamWriter(client.getOutputStream()))) {

            String in = inFromClient.readLine(), out;
            while(in != null){
                out = in + " from server";
                outToClient.write(out);
                outToClient.newLine();
                outToClient.flush();
                in = inFromClient.readLine();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

请注意，此解决方案使用 Javas ARM(自动资源管理)来自动关闭流和套接字。所以这在 java 1.7 之前是行不通的!