QTcpSocket双向客户端 - 服务器通信

Question

我正在为基于套接字接口的Raspberry PI开发应用程序.主要的想法是Raspberry将连接到传感器,收集数据并通过WiFi将其发送到Android设备.从Android我可以与传感器发送一些命令进行通信.我是这种开发的初学者,并且关于QTcpSocket的一些教程我已经创建了一个简单的客户端 - 服务器应用程序,但它只是在一个方向.服务器侦听客户端发送的内容.你能帮助我把它改进为双向沟通吗？我已经读过QTcpSocket不需要线程来解决这类问题,但我找不到任何解决方案.

我将不胜感激任何帮助!

server.cpp:

#include "server.h"
#include <QTcpServer>
#include <QTcpSocket>
#include <cstdio>
#include <QtDebug>

Server::Server(QObject *parent) :
QObject(parent)
{
    server = new QTcpServer(this);
    connect(server, SIGNAL(newConnection()),
    this, SLOT(on_newConnection()));
}

void Server::listen()
{
    server->listen(QHostAddress::Any, 5100);
}

void Server::on_newConnection()
{
    socket = server->nextPendingConnection();

    if(socket->state() == QTcpSocket::ConnectedState)
    {
        printf("New connection established.\n");
        qDebug()<<socket->peerAddress();
    }
    connect(socket, SIGNAL(disconnected()),
    this, SLOT(on_disconnected()));
    connect(socket, SIGNAL(readyRead()),
    this, SLOT(on_readyRead()));
}

void Server::on_readyRead()
{
    while(socket->canReadLine())
    {
        QByteArray ba = socket->readLine();

        if(strcmp(ba.constData(), "!exit\n") == 0)
        {
            socket->disconnectFromHost();
            break;
        }
        printf(">> %s", ba.constData());
    }
}

void Server::on_disconnected()
{
    printf("Connection disconnected.\n");
    disconnect(socket, SIGNAL(disconnected()));
    disconnect(socket, SIGNAL(readyRead()));
    socket->deleteLater();
}

client.cpp

#include "client.h"
#include <QTcpSocket>
#include <QHostAddress>
#include <cstdio>

Client::Client(QObject *parent) : QObject(parent)
{
    socket = new QTcpSocket(this);
    printf("try to connect.\n");
    connect(socket, SIGNAL(connected()),
    this, SLOT(on_connected()));
}

void Client::on_connected()
{
    printf("Connection established.\n");
    char buffer[1024];
    forever
    {
        while(socket->canReadLine())
        {
            QByteArray ba = socket->readLine();
            printf("from server: %s", ba.constData());
        }
        printf(">> ");
        gets(buffer);
        int len = strlen(buffer);
        buffer[len] = '\n';
        buffer[len+1] = '\0';
        socket->write(buffer);
        socket->flush();
    }

}

void Client::connectToServer()
{
    socket->connectToHost(QHostAddress::LocalHost, 5100);
}

Answer 1

从架构的角度来看,您应该首先在服务器和客户端之间定义一些通信规则(消息流).

然后根据定义的流程从(到)QTCPSocket实例读取(写入).

例如,您可以在服务器端读取数据,检查应该回答的内容,并将响应写入您已阅读的同一个套接字.对于面向行的消息(并且仅针对它们),代码可能如下所示:

    void Server::on_readyRead()
    {
        // "while" loop would block until at least one whole line arrived
        // I would use "if" instead
        if(socket->canReadLine()) 
        {
            QByteArray ba = socket->readLine();

            QByteArray response;

            // some code which parses arrived message
            // and prepares response

            socket->write(response);
        }
        //else just wait for more data
    }

就个人而言,我会从on_readyRead()插槽中移出解析并发送响应以避免阻塞事件循环太长时间,但由于您是网络编程的初学者,我只是想澄清实现双向通信可以做些什么.

有关详细信息,请参阅http://qt-project.org/doc/qt-4.8/qtnetwork.html

记住检查整个消息是否已在客户端和服务器端都到达.如果您使用自己的协议(不是HTTP,FTP或其他标准),您可以在消息的开头添加消息长度.