QTcpSocket、QTcpServer基本用法

英文注释都是从Qt助手里面抄的，英语不好，就不翻译了。

在启动程序的时候，要先启动服务端，然后再启动客户端才能建立连接，如果先启动客户端，再启动服务端，就连接不上了。

我是想在客户端开一个死循环一直检测是否连接成功，然后不停的连接，直到连上，跳出循环，这样就算先启动客户端也可以连接上。

Client:

//widget.h
#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QHBoxLayout>
#include <QVBoxLayout>
#include <QPushButton>
#include <QTextEdit>
#include <QTcpSocket>
#include <QAbstractSocket>
#include <QByteArray>
#include <QString>

class Widget : public QWidget
{
Q_OBJECT

public:
Widget(QWidget *parent = 0);
~Widget();
void initUi(); //初始化界面
void newTcpConnect(); //创建新的连接
private slots:
void sendMessage(); //发送消息
void receiveMessage(); //接收消息
private:
QTextEdit *myEdit,*yourEdit;
QPushButton *sendButton,*closeButton;
QHBoxLayout *hlayout;
QVBoxLayout *vlayout,*alllayout;

QTcpSocket *tcpSocket;
};

#endif // WIDGET_H

//widget.cpp
#include "widget.h"

Widget::Widget(QWidget *parent)
: QWidget(parent)
{
initUi();
connect(sendButton,SIGNAL(clicked(bool)),this,SLOT(sendMessage()));
connect(closeButton,SIGNAL(clicked(bool)),this,SLOT(close()));
tcpSocket = new QTcpSocket;
newTcpConnect();
//This signal is emitted once every time new data is available for reading from the device.
connect(tcpSocket,SIGNAL(readyRead()),SLOT(receiveMessage()));
}

Widget::~Widget()
{
delete tcpSocket;
}

void Widget::initUi()
{
this->resize(500,500);
this->setWindowTitle("Client");

sendButton = new QPushButton("send",this);
closeButton = new QPushButton("close",this);
myEdit = new QTextEdit(this);
yourEdit = new QTextEdit(this);

hlayout = new QHBoxLayout;
hlayout->addStretch(6);
hlayout->addWidget(closeButton);
hlayout->addWidget(sendButton);

vlayout = new QVBoxLayout;
vlayout->addWidget(yourEdit,2);
vlayout->addWidget(myEdit,1);

alllayout = new QVBoxLayout;
alllayout->addLayout(vlayout);
alllayout->addLayout(hlayout);

this->setLayout(alllayout);
}

void Widget::newTcpConnect()
{
//Aborts the current connection and resets the socket.
//Unlike disconnectFromHost(), this function immediately closes the socket, discarding any pending data in the write buffer.
tcpSocket->abort();
//Attempts to make a connection to hostName on the given port.
tcpSocket->connectToHost("127.0.0.1",9999);

}

void Widget::sendMessage()
{
QString str = myEdit->toPlainText();
yourEdit->append(str);
myEdit->clear();
QByteArray data = str.toUtf8();
tcpSocket->write(data);
}

void Widget::receiveMessage()
{
//Reads all remaining data from the device, and returns it as a byte array.
QByteArray data = tcpSocket->readAll();
QString str(data);
yourEdit->append(str);
}

Server:

//widget.h
#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QHBoxLayout>
#include <QVBoxLayout>
#include <QPushButton>
#include <QTextEdit>
#include <QTcpSocket>
#include <QTcpServer>
#include <QAbstractSocket>
#include <QByteArray>
#include <QString>

class Widget : public QWidget
{
Q_OBJECT

public:
Widget(QWidget *parent = 0);
~Widget();
void initUi(); //初始化界面
void newListen(); //建立tcp监听事件
private slots:
void acceptConnect(); //接受客户端连接
void sendMessage(); //发送消息
void receiveMessage(); //接收消息
private:
QTextEdit *myEdit,*yourEdit;
QPushButton *sendButton,*closeButton;
QHBoxLayout *hlayout;
QVBoxLayout *vlayout,*alllayout;

QTcpServer *tcpServer;
QTcpSocket *tcpSocket;
};

#endif // WIDGET_H

//widget.cpp
#include "widget.h"

Widget::Widget(QWidget *parent)
: QWidget(parent)
{
initUi();
tcpSocket = new QTcpSocket;
tcpServer = new QTcpServer;
newListen();
//This signal is emitted every time a new connection is available.
connect(tcpServer,SIGNAL(newConnection()),SLOT(acceptConnect()));
//This signal is emitted after an error occurred.
//The socketError parameter describes the type of error that occurred.
connect(tcpSocket,SIGNAL(error(QAbstractSocket::SocketError)),this,SLOT(close()));
}

Widget::~Widget()
{
delete tcpSocket;
delete tcpServer;
}

void Widget::initUi()
{
this->resize(500,500);
this->setWindowTitle("Server");

sendButton = new QPushButton("send",this);
closeButton = new QPushButton("close",this);
myEdit = new QTextEdit(this);
yourEdit = new QTextEdit(this);

connect(sendButton,SIGNAL(clicked(bool)),this,SLOT(sendMessage()));
connect(closeButton,SIGNAL(clicked(bool)),this,SLOT(close()));

hlayout = new QHBoxLayout;
hlayout->addStretch(6);
hlayout->addWidget(closeButton);
hlayout->addWidget(sendButton);

vlayout = new QVBoxLayout;
vlayout->addWidget(yourEdit,2);
vlayout->addWidget(myEdit,1);

alllayout = new QVBoxLayout;
alllayout->addLayout(vlayout);
alllayout->addLayout(hlayout);

this->setLayout(alllayout);
}

void Widget::newListen()
{
//Tells the server to listen for incoming connections on address address and port port.
//If port is 0, a port is chosen automatically. If address is QHostAddress::Any, the server will listen on all network interfaces.
if(!tcpServer->listen(QHostAddress::Any,9999))
{
qDebug()<<tcpServer->errorString();
tcpServer->close();
}
}

void Widget::acceptConnect()
{
//Returns the next pending connection as a connected QTcpSocket object.
tcpSocket = tcpServer->nextPendingConnection();
connect(tcpSocket,SIGNAL(readyRead()),SLOT(receiveMessage()));
}

void Widget::sendMessage()
{
QString str = myEdit->toPlainText();
yourEdit->append(str);
myEdit->clear();
QByteArray data = str.toUtf8();
tcpSocket->write(data);
}

void Widget::receiveMessage()
{
QByteArray data = tcpSocket->readAll();
QString str(data);
yourEdit->append(str);
}