套接字问题- readline无法正常工作

Question

我尝试使用套接字编写客户端和服务器连接。问题是我的客户端无法读取来自服务器的响应(它挂在readline上)。

以下是部分代码。

服务器：

    try {
        // Create the server socket.
        portNumber = Integer.parseInt(myParam.get("socket.portNumber"));
        System.out.println(portNumber);
        mainSocket = new ServerSocket(portNumber);

    } catch (IOException ioe) {
        System.out.println("Error Message : "+ioe.getMessage());
    }

    while(true)
    {     
        try
        {
            // Accept connections
            Socket clientSocket = mainSocket.accept();
            SocketServerThread st = new SocketServerThread (clientSocket);
            st.start();
        }
        catch(IOException ioe)
        {
            System.out.println("Error message :"+ioe.getMessage());
        }
    }

主线：

public void run() {

    BufferedReader in = null;
    PrintWriter out = null;
    String clientResponse = null;

    try {
        in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
        out = new PrintWriter(new OutputStreamWriter(clientSocket.getOutputStream()));

        //Read The Message
        String clientRequest = in.readLine();
        System.out.println("Message recieved : " + clientRequest);

        //Process the message

        // Send response
        out.println(clientResponse+"\n");
        out.flush();
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        // Clean up
        try {
            in.close();
            out.close();
            clientSocket.close();
        } catch (IOException ioe) {
            ioe.printStackTrace();
        }
    }

客户端：

    try {
        // Create the server socket.
        simSocket = new Socket("192.168.52.27", portNumber);
    } catch (IOException ioe) {
        System.out.println("Error Message : " + ioe.getMessage());
    }
    BufferedReader in = null;
    PrintWriter out = null;
    try {
        in = new BufferedReader(new InputStreamReader(simSocket.getInputStream()));
        out = new PrintWriter(new OutputStreamWriter(simSocket.getOutputStream()));

            out.write("My message");
            out.flush();

            do{
            response = in.readLine(); //This is where the code hang
            }while (response.length()<= 0);

            System.out.print(response);

    } catch (IOException ioe) {
        System.out.println("Error message :" + ioe.getMessage());
    } finally {
        try {
            in.close();
            out.close();
            simSocket.close();
        } catch (IOException ioException) {
            ioException.printStackTrace();
        }
    }

你们能告诉我出了什么问题吗？非常感谢你的帮助

Answer 1

好的，我已经弄清楚了。挂起的不是客户端，而是服务器。它尝试从客户端读取一行文本，但客户端没有发送行分隔符：

    out.write("My message");
    out.flush();

在这里用println()替换write()。

Answer 2

好了，我在代码中做了几次编辑，现在它运行得很好：

服务器：

    try {
        // Create the server socket.
        portNumber = Integer.parseInt(myParam.get("socket.portNumber"));
        mainSocket = new ServerSocket(portNumber);

    } catch (IOException ioe) {
        System.out.println("Error Message : " + ioe.getMessage());
    }

    // Accept connections    
    try {
        clientSocket = mainSocket.accept();
    } catch (IOException ioe) {
        System.out.println("Error Message : " + ioe.getMessage());
    }
    BufferedReader in = null;
    PrintWriter out = null;

    while (true) {
        try {
            in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
            out = new PrintWriter(new OutputStreamWriter(clientSocket.getOutputStream()));
            //Read The Message
            **StringBuffer buffer = new StringBuffer();
            while (true) {
                int ch = in.read();
                if ((ch < 0) || (ch == '\n')) {
                    break;
                }
                buffer.append((char) ch);
            }
            String clientRequest = buffer.toString();**

            SocketServerThread st = new SocketServerThread(clientRequest, out);
            st.start();
        } catch (IOException ioe) {
            System.out.println("Can't accept connection. Error message :" + ioe.getMessage());
        }
    }

我用read修改了readline，它工作了，所以"\n“是问题的假设是正确的。

线程:线程中的一个小变化(删除读取请求部分，因为我已经在服务器中完成了该部分)

客户端:将readline更改为read，就像服务器端一样。

感谢大家的帮助

Answer 3

out.write("My message");

这不会发送行终止符，因此它永远不会被读取。使用println()。

out.println(clientResponse+"\n");

这将发送clientResponse +换行符+a \n。最后一部分可能会被解释为空行。这没有多大意义。删除\n。

do{
    response = in.readLine(); //This is where the code hang
}while (response.length()<= 0);

这不是读行的正确方式。它将在EOS上获得NPE；响应长度永远不能为负；为什么要给自己发送空行？正确的方法是：

while ((response = in.readLine()) != null) {
    // if (response.length() == 0) continue; // if you must
    // process the line
}
// when you get here EOS has occurred.