QT使用tcp链接例子

在QT中，使用TCP连接可以通过`QTcpSocket`类来实现。以下是一个基本的例子，展示了如何创建一个客户端和服务端的TCP连接：

**服务端（Server.cpp）:**

#include <QTcpServer>
#include <QObject>

class Server : public QObject {
    Q_OBJECT
public:
    explicit Server(QObject *parent = nullptr) : QObject(parent) {
        server = new QTcpServer(this);
        connect(server, &QTcpServer::newConnection, this, &Server::handleNewConnection);
        if (!server->listen(QHostAddress::Any, 12345)) { // 使用任意IP地址监听12345端口
            qCritical() << "Listen failed: " << server->errorString();
        }
    }

private slots:
    void handleNewConnection() {
        QTcpSocket *client = server->nextPendingConnection();
        connect(client, &QTcpSocket::readyRead, this, &Server::readData);
        connect(client, &QTcpSocket::disconnected, this, &Server::connectionClosed);
    }

private:
    QTcpServer *server;
};

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    Server server;
    return app.exec();
}

**客户端（Client.cpp）:**

#include <QTcpSocket>
#include <QObject>
#include <QApplication>

class Client : public QObject {
    Q_OBJECT
public:
    explicit Client(const QString& host, quint16 port, QObject *parent = nullptr)
        : QObject(parent), socket(new QTcpSocket(this))
    {
        connect(socket, &QTcpSocket::connected, this, &Client::onConnected);
        connect(socket, &QTcpSocket::disconnected, this, &Client::onDisconnected);
        connect(socket, &QTcpSocket::readyRead, this, &Client::readData);

        socket->connectToHost(host, port); // 连接到服务器
    }

private slots:
    void onConnected() {
        socket->write("Hello from client!"); // 发送数据到服务器
    }

    void readData() {
        QByteArray data = socket->readAll();
        qDebug() << "Received data: " << data;
    }

    void onDisconnected() {
        qDebug() << "Connection closed";
    }

private:
    QTcpSocket *socket;
};

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    Client client("localhost", 12345); // 本地主机，假设服务端在本机运行
    return app.exec();
}

在这个例子中，服务端创建一个`QTcpServer`并监听，当有新的连接请求时，它会创建一个新的`QTcpSocket`实例并传递给`handleNewConnection`槽函数。客户端则连接到服务端，并在连接成功后发送消息。