1.Qt中TCP客户端编程

对Qt编程而言，网络只是数据传输的通道；Qt提供了QTcpSocket类（封装了TCP协议细节）；将QTcpSocket的对象当做黑盒使用，进行数据首发。

1.1QTcpSocket类的继承

1.2QTcpSocket的使用

连接服务器主机（connectToHost()）发送数据/接受数据（write()/read()）关闭连接（close()）

1.3QTcpSocket的注意事项

默认情况下，QTcpSocket使用异步编程的方式 操作完成后立即返回（返回只代表的操作开始，不代表操作的结果，类似C语言中的回调函数以及Qt中的信号和槽机制）通过发送信号的方式返回操作的结果

2.QTcpSocket同步编程

2.1QTcpSocket提供辅助函数可完成同步编程的方式（返回值代表返回结果，平时编程使用的大多是同步编程的方式）

- waitForConnected()/waitForDisconnected() - waitForBytesWritten()/waitForReadyRead()

2.2QTcpSocket同步编程流程

调用完功能函数（如connectToHost）立刻调用对应的同步辅助函数即实现同步编程

2.3QTcpSocket同步编程代码

代码运行时需启动socket的服务程序模拟tcp服务端

 main.cpp

#include "clientdemo.h" #include <QtGui/QApplication> #include <QTcpSocket> #include <QDebug> void SyncClientDemo() { QTcpSocket client; char buf[256] = {0}; client.connectToHost("127.0.0.1", 8080); qDebug() << "Connected:" << client.waitForConnected(); qDebug() << "Send Bytes:" << client.write("D.T.Software"); qDebug() << "Send Status:" << client.waitForBytesWritten(); qDebug() << "Data Available:" << client.waitForReadyRead(); qDebug() << "Received Bytes:" << client.read(buf, sizeof(buf)-1); qDebug() << "Received Data:" << buf; client.close(); // client.waitForDisconnected(); } int main(int argc, char *argv[]) { QApplication a(argc, argv); SyncClientDemo(); //ClientDemo w; //w.show(); return a.exec(); }

 ClientDemo.cpp

#include "ClientDemo.h" #include <QHostAddress> #include <QDebug> ClientDemo::ClientDemo(QObject* parent) : QObject(parent) { connect(&m_client, SIGNAL(connected()), this, SLOT(onConnected())); connect(&m_client, SIGNAL(disconnected()), this, SLOT(onDisconnected())); connect(&m_client, SIGNAL(readyRead()), this, SLOT(onDataReady())); connect(&m_client, SIGNAL(bytesWritten(qint64)), this, SLOT(onBytesWritten(qint64))); } void ClientDemo::onConnected() { qDebug() << "onConnected"; qDebug() << "Local Address:" << m_client.localAddress(); qDebug() << "Local Port:" << m_client.localPort(); } void ClientDemo::onDisconnected() { qDebug() << "onDisconnected"; } void ClientDemo::onDataReady() { char buf[256] = {0}; qDebug() << "onDataReady:" << m_client.read(buf, sizeof(buf)-1); qDebug() << "Data:" << buf; } void ClientDemo::onBytesWritten(qint64 bytes) { qDebug() << "onBytesWritten:" << bytes; } void ClientDemo::connectTo(QString ip, int port) { m_client.connectToHost(ip, port); } qint64 ClientDemo::send(const char* data, int len) { return m_client.write(data, len); } qint64 ClientDemo::available() { return m_client.bytesAvailable(); } void ClientDemo::close() { m_client.close(); }

结果

3.QTcpSocket异步编程

3.1 QTcpSocket的异步编程

QTcpSocket的对象通过发送信号的方式返回操作结果可以在程序中将对应的信号连接到槽函数，获取结果在GUI应用程序中通常使用QTcpSocket的异步编程方式

3.2QTcpSocket中的关键信号

connected():成功连接远端主机disconnected：远程主机断开连接readyRead()：远端主机数据到达本机bytesWritten(qint64)：数据成功发送至系统（OS）

3.3编程实践

clientdemo.h

#ifndef CLIENTDEMO_H #define CLIENTDEMO_H #include <QObject> //#include "ui_clientdemo.h" #include <QTcpSocket> class ClientDemo : public QObject { Q_OBJECT QTcpSocket m_client; protected slots: void onConnected(); void onDisconnected(); void onDataReady(); void onBytesWritten(qint64 bytes); public: qint64 send(const char* data, int len); qint64 available();//得到到达本机的数据长度 ClientDemo(QObject *parent = NULL); void connectToHost(QString ip,int port); void close(); ~ClientDemo(); private: // Ui::ClientDemoClass ui; }; #endif // CLIENTDEMO_H

clientdemo.cpp

#include "clientdemo.h" #include <QDebug> ClientDemo::ClientDemo(QObject *parent): QObject(parent) { //ui.setupUi(this); connect(&m_client, SIGNAL(connected()), this, SLOT(onConnected()) ); connect(&m_client, SIGNAL(disconnected()), this, SLOT(onDisconnected())); connect(&m_client, SIGNAL(readyRead()), this, SLOT(onDataReady())); connect(&m_client, SIGNAL(bytesWritten(qint64)), this, SLOT(onBytesWritten(qint64))); } void ClientDemo::onConnected() { qDebug() << "onConnected"; qDebug() << "Local Address:" ;//<< m_client.localAddress(); qDebug() << "Local Port:" << m_client.localPort(); } void ClientDemo::onDisconnected() { qDebug() << "onDisconnected"; } void ClientDemo::onDataReady() { char buf[256] = {0}; qDebug() << "onDataReady:" << m_client.read(buf, sizeof(buf)-1); qDebug() << "Data:" << buf; } void ClientDemo::onBytesWritten(qint64 bytes) { qDebug() << "onBytesWritten:" << bytes; } void ClientDemo::connectToHost(QString ip,int port) { m_client.connectToHost(ip, port); } qint64 ClientDemo::send(const char* data, int len) { return m_client.write(data, len); } qint64 ClientDemo::available() { return m_client.bytesAvailable(); } void ClientDemo::close() { m_client.close(); } ClientDemo::~ClientDemo() { }

main.cpp

#include "clientdemo.h" #include <QtGui/QApplication> #include <QTcpSocket> #include <QDebug> int main(int argc, char *argv[]) { QApplication a(argc, argv); //SyncClientDemo(); ClientDemo w; w.connectToHost("127.0.0.1",8080); char buf[]="abc"; w.send(buf,sizeof(buf)-1); //w.show(); return a.exec(); }

结果

4.小结

Qt提供了QTcpSocket类，其对象可用于收发TCP数据QTcpSocket默认使用异步编程方式QTcpSocket提供辅助函数用于完成同步编程的方式GUI应用程序通常使用QTcpSocket的异步编程方式