无法使用socket.recv从服务器接收数据

问题描述

我有一个python客户端，它以json格式向Java服务器发送一些数据（名称空间，metric_name，时间戳，metric_value，维度）并接收响应。

这是客户端代码的一部分：

def _init_socket(self):
    logger.info("initial socket,hostname {},port {}".format(self.host,self.port))
    client = socket.socket(socket.AF_INET,socket.soCK_STREAM)
    address = (self.host,self.port)
    client.connect(address)
    self.client = client

def send_put_metrics_request(self,namespace,metric_name,metric_value,dimensions): 
    try:
        self._init_socket()
        timestamp = int(round(time.time() * 1000))
        send_data = self.convert_to_json(namespace,timestamp,dimensions)
        self.client.send(bytes(send_data + "\n",encoding=self.encoding))
        self.client.shutdown(socket.SHUT_WR)

        data = self.client.recv(1024)
        print(data)

    finally:
        self.client.close()

在服务器端，我只想将HelloWorld返回给客户端。这是Java服务器代码的一部分：

    public void start() {
        logger.info("Daemon Server is listening for metrics");

        try (final ServerSocket serverSocket = new ServerSocket()) {
            final int port = 7072;
            serverSocket.bind(new InetSocketAddress(port));

            while (true) {
                final Socket socket = serverSocket.accept();
                threadPool.submit(() -> process(socket));
            }
        } catch (final Exception e) {
            logger.error(Thread.currentThread().getId() + " Failed to make a connection to the server socket"
                + e.getMessage());
            throw new ConnectToServerSocketException(Thread.currentThread().getId()
                + " Failed to make a connection to the server socket" + e.getMessage());
        } finally {
            threadPool.shutdown();
        }
    }


    protected void process(final Socket socket) {
        final Message message;
        try (final InputStream input = socket.getInputStream()) {
            final OutputStream output = socket.getoutputStream();
            final OutputStreamWriter osw = new OutputStreamWriter(output,"UTF8");
            final PrintWriter writer = new PrintWriter(new BufferedWriter(osw));
            message = objectMapper.readValue(inputStreamToString(input),Message.class);
// pls ignore the below line,it just calls another method to do something
            final String res = forwardMetrics(message);
            logger.info("Thread " + Thread.currentThread().getId() + " processed result: " + res);

            writer.println("HelloWorld"+"\n");
            writer.flush();
            socket.close();
            logger.info("Socket closed")

        } catch (final IOException e) {
            logger.error(e.getMessage());
            logger.error("Daemon server Failed to read input from socket");
            throw new ReadFromSocketException("Failed to read input from socket",e);
        }

    }

然后，我启动服务器并通过客户端以正确的格式发送了请求。我没有从客户端获得“ HelloWorld”。打印结果仅为 b''。从服务器端的日志开始，它执行了所有行，直到套接字关闭。

我想知道为什么没有打印出来。

解决方法

不能保证客户端中的socket.recv()将在首次提取时返回响应。建议您在while循环中调用recv()，直到收到None。