Qt实现TCP通信

QT5.5.0实现TCP网络通信

创建TCP服务器

1.实例化QTCPSocket和QTCPServer

//创建了一个MyTCPServer类,定义了一个获取IP的方法
//其基类为QTcpServer
class MyTCPServer : public QTcpServer
{
    Q_OBJECT
public:
    explicit MyTCPServer(QObject *parent = 0);
    void GetLocalIP(QList<QHostAddress> &IPList,QStringList &ipshow);
signals:
public slots:
};

//创建一个QTcpSocket对象
tcp_socket = new QTcpSocket(this);
//创建一个MyTCPServer对象
tcp_server = new MyTCPServer(this);

2.检测IP连接

void MyTCPServer::GetLocalIP(QList<QHostAddress> &IPList,QStringList &ipshow)
{
    //获取本机IP地址列表
    QList<QNetworkInterface> list=QNetworkInterface::allInterfaces();
    foreach (QNetworkInterface interface, list) {
        QList<QNetworkAddressEntry> entrylist=interface.addressEntries();
        //只使用IPV4地址
        foreach (QNetworkAddressEntry entry, entrylist) {
            if(entry.ip().protocol()==QAbstractSocket::IPv4Protocol)
            {
                IPList<<entry.ip();
                ipshow<<entry.ip().toString();
            }
        }
    }
}

3.TCP服务器具有监听功能,能够与其他的客户端建立连接

void Widget::startListen()
{
    if(ui->addressbox->currentIndex()!=-1)
    {
        qDebug()<<"Start listening";
        //使用QTcpServer下的listen开启监听
        tcp_server->listen(IPList[ui->addressbox->currentIndex()],ui->portbox->currentText().toShort());
        
        ui->textBrowser->append("The server ip is "+ui->addressbox->currentText());
        
        ui->textBrowser->append("The server is listening port "+ui->portbox->currentText());
    }
}

4.QTCPServer提供了新客户端连接的信号，当有新用户连接时能够自动触发该信号，我们通过该信号执行客户端连接槽函数

//客户端信号槽连接
connect(tcp_server,&MyTCPServer::newConnection,this,&Widget::clientConnected);
//槽函数
void Widget::clientConnected()
{
    qint16 port;

    QString ip;
	//新客户端连接将返回一个QTCPSocket类型，当服务器被摧毁时他会被自动释放
    tcp_socket = tcp_server->nextPendingConnection();

    ip = tcp_socket->peerAddress().toString();

    port = tcp_socket->peerPort();

    ui->textBrowser->append("Client connected");

    ui->textBrowser->append("The ip address is"+ip);

    ui->textBrowser->append("The port number is "+ QString::number(port));

    //接收消息就绪信号，当接收到客户端发送的消息时出触发该信号
    //在槽函数内处理接收的数据，特别注意该连接调用的位置，该连接调用必须在nextPendingConnection（）之后否则会出现无法接收客户端数据的问题
    //初步理解是只有当新的客户端连接之后再调用QTCPSocket的该连接才生效
    connect(tcp_socket,&QTcpSocket::readyRead,this,&Widget::reciveMessage);
	//这里的连接同样如此
    connect(tcp_socket,&QTcpSocket::stateChanged,this,&Widget::tcpStateChange);

}

5.接收数据槽函数

void Widget::reciveMessage()
{
    //接收通过tcp_socket中的readAll()方法实现
    QString message="Client:"+tcp_socket->readAll();
    ui->textBrowser->append(message);
}

6.发送槽函数

void Widget::sendMessage()
{
    if(NULL==tcp_socket)
        return;
    if(tcp_socket->state()==tcp_socket->ConnectedState)
    {
        ui->textBrowser->append("Server:"+ui->sendedit->toPlainText());
        //发送数据通过tcp_socket中的write方法实现
        tcp_socket->write(ui->sendedit->toPlainText().toLatin1());
    }
}

创建TCP客户端

​ 1.TCP客户端需要选择服务器地址以及端口号，然后请求建立连接。

void Widget::toConnect()
{
    if(tcp_socket->state()!=tcp_socket->ConnectedState)
    {
        //客户端地址,暂时先通过直接设定
        IPList[ui->addressbox->currentIndex()]="192.168.1.17";
        
        qDebug()<<IPList[ui->addressbox->currentIndex()]<<ui->portbox->currentText();
        //通过tcp_socket中的connectToHost与服务器进行连接
        tcp_socket->connectToHost(IPList[ui->addressbox->currentIndex()],ui->portbox->currentText().toShort());
    }
}

​ 2.检测连接状态

void Widget::tcpStateChange(QAbstractSocket::SocketState state)
{
    switch (state) {
    case QAbstractSocket::UnconnectedState:
        ui->textBrowser->append("Socket state:UnconnectedState");
        break;
    case QAbstractSocket::ConnectedState:
        ui->textBrowser->append("Socket state:ConnectedState");
        break;
    case QAbstractSocket::ConnectingState:
        ui->textBrowser->append("Socket state:ConnectingState");
        break;
    case QAbstractSocket::ListeningState:
        ui->textBrowser->append("Socket state:ListeningState");
        break;
    default:
        break;
    }
}

3.客户端的发送和接收消息与服务器端一样