Qt NetWork即时通讯网络聊天室（基于TCP）

本文使用QT的网络模块来创建一个网络聊天室程序，主要包括以下功能：

1、基于TCP的可靠连接（QTcpServer、QTcpSocket）

2、一个服务器，多个客户端

3、服务器接收到某个客户端的请求以及发送信息，经该信息重定向发给其它客户端

最终实现一个共享聊天内容的聊天室！

开发测试环境：QT5.12.0 + Qt Creator 4.8.0 + MinGW7.3

代码如下：

1、服务器 QtInstantMessagingServer

基于Console的应用程序，因为这里不需要界面。

QT += core network
QT -= gui

 Server.h

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#ifndef SERVER_H
#define SERVER_H

#include <QObject>
#include <QTcpServer>
#include <QTcpSocket>
#include <QDebug>
#include <QVector>

class Server : public QObject
{
 Q_OBJECT
public:
 explicit Server(QObject *parent = nullptr);

 void startServer();
 void sendMessageToClients(QString message);

signals:

public slots:
 void newClientConnection();
 void socketDisconnected();
 void socketReadyRead();
 void socketStateChanged(QAbstractSocket::SocketState state);

private:
 QTcpServer* chatServer;
 QVector<QTcpSocket*>* allClients;
};

#endif // SERVER_H

 Server.cpp

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#include "Server.h"

Server::Server(QObject *parent) : QObject(parent)
{

}

void Server::startServer()
{
 // store all the connected clients
 allClients = new QVector<QTcpSocket*>;
 // created a QTcpServer object called chatServer
 chatServer = new QTcpServer();
 // limit the maximum pending connections to 10 clients.
 chatServer->setMaxPendingConnections(10);
 // The chatServer will trigger the newConnection() signal whenever a client has connected to the server.
 connect(chatServer, SIGNAL(newConnection()), this, SLOT(newClientConnection()));
 // made it constantly listen to port 8001.
 if (chatServer->listen(QHostAddress::Any, 8001))
 {
 qDebug() << "Server has started. Listening to port 8001.";
 }
 else
 {
 qDebug() << "Server failed to start. Error: " + chatServer->errorString();
 }

}

void Server::sendMessageToClients(QString message)
{
 if (allClients->size() > 0)
 {
 // we simply loop through the allClients array and pass the message data to all the connected clients.
 for (int i = 0; i < allClients->size(); i++)
 {
 if (allClients->at(i)->isOpen() && allClients->at(i)->isWritable())
 {
 allClients->at(i)->write(message.toUtf8());
 }
 }
 }

}

void Server::newClientConnection()
{
 // Every new client connected to the server is a QTcpSocket object,
 // which can be obtained from the QTcpServer object by calling nextPendingConnection().
 QTcpSocket* client = chatServer->nextPendingConnection();
 // You can obtain information about the client
 // such as its IP address and port number by calling peerAddress() and peerPort(), respectively.
 QString ipAddress = client->peerAddress().toString();
 int port = client->peerPort();
 // connect the client's disconnected(),readyRead() and stateChanged() signals to its respective slot function.
 // 1、When a client is disconnected from the server, the disconnected() signal will be triggered
 connect(client, &QTcpSocket::disconnected, this, &Server::socketDisconnected);
 // 2、whenever a client is sending in a message to the server, the readyRead() signal will be triggered.
 connect(client, &QTcpSocket::readyRead, this, &Server::socketReadyRead);
 // 3、 connected another signal called stateChanged() to the socketStateChanged() slot function.
 connect(client, &QTcpSocket::stateChanged, this, &Server::socketStateChanged);
 // store each new client into the allClients array for future use.
 allClients->push_back(client);
 qDebug() << "Socket connected from " + ipAddress + ":" + QString::number(port);
}

// When a client is disconnected from the server, the disconnected() signal will be triggered
void Server::socketDisconnected()
{
 // displaying the message on the server console whenever it happens, and nothing more.
 QTcpSocket* client = qobject_cast<QTcpSocket*>(QObject::sender());
 QString socketIpAddress = client->peerAddress().toString();
 int port = client->peerPort();
 qDebug() << "Socket disconnected from " + socketIpAddress + ":" + QString::number(port);
}

// whenever a client is sending in a message to the server, the readyRead() signal will be triggered.
void Server::socketReadyRead()
{
 // use QObject::sender() to get the pointer of the object that emitted the readyRead signal
 // and convert it to the QTcpSocket class so that we can access its readAll() function.
 QTcpSocket* client = qobject_cast<QTcpSocket*>(QObject::sender());
 QString socketIpAddress = client->peerAddress().toString();
 int port = client->peerPort();
 QString data = QString(client->readAll());
 qDebug() << "Message: " + data + " (" + socketIpAddress + ":" + QString::number(port) + ")";
 // redirect the message, just passing the message to all connected clients.
 sendMessageToClients(data);
}

// This function gets triggered whenever a client's network state has changed,
// such as connected, disconnected, listening, and so on.
void Server::socketStateChanged(QAbstractSocket::SocketState state)
{
 QTcpSocket* client = qobject_cast<QTcpSocket*>(QObject::sender());
 QString socketIpAddress = client->peerAddress().toString();
 int port = client->peerPort();
 QString desc;
 // simply print out a relevant message according to its new state
 if (state == QAbstractSocket::UnconnectedState)
 desc = "The socket is not connected.";
 else if (state == QAbstractSocket::HostLookupState)
 desc = "The socket is performing a host name lookup.";
 else if (state == QAbstractSocket::ConnectingState)
 desc = "The socket has started establishing a connection.";
 else if (state == QAbstractSocket::ConnectedState)
 desc = "A connection is established.";
 else if (state == QAbstractSocket::BoundState)
 desc = "The socket is bound to an address and port.";
 else if (state == QAbstractSocket::ClosingState)
 desc = "The socket is about to close (data may still be waiting to be written).";
 else if (state == QAbstractSocket::ListeningState)
 desc = "For internal use only.";
 qDebug() << "Socket state changed (" + socketIpAddress + ":" + QString::number(port) + "): " + desc;
}

Main.cpp

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#include <QCoreApplication>
#include "Server.h"

int main(int argc, char *argv[])
{
 QCoreApplication a(argc, argv);

 Server* myServer = new Server();
 myServer->startServer();

 return a.exec();
}

2、客户端QtInstantMessagingClient

基于Widget的应用程序，客户端需要一个友好的界面，父类QMainWindow，MainWindow.ui定义界面如下：

可以给不同的客户端取个名字，如“Michael”、“James”等等，点击“Connect”按钮连接服务端，此时Label变为“Disconnect”。

QT += core gui network

 MainWindow.h

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#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QDebug>
#include <QTcpSocket>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
 Q_OBJECT

public:
 explicit MainWindow(QWidget *parent = nullptr);
 ~MainWindow();

private slots:
 void on_connectButton_clicked();
 void socketConnected();
 void socketDisconnected();
 void socketReadyRead();

 void on_sendButton_clicked();

private:
 Ui::MainWindow* ui;
 bool connectedToHost;
 QTcpSocket* socket;

 void printMessage(QString message);
};

#endif // MAINWINDOW_H

 MainWindow.cpp

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#include "MainWindow.h"
#include "ui_MainWindow.h"

MainWindow::MainWindow(QWidget *parent) :
 QMainWindow(parent),
 ui(new Ui::MainWindow)
{
 ui->setupUi(this);
 connectedToHost = false;
}

MainWindow::~MainWindow()
{
 delete ui;
}

void MainWindow::on_connectButton_clicked()
{
 if (!connectedToHost)
 {
 // create a QTcpSocket object called socket and make it connect to a host at 127.0.0.1 on port 8801.
 socket = new QTcpSocket();
 // connected the socket object to its respective slot functions when connected(),disconnected(), and readReady() signals were triggered.
 // This is exactly the same as the server code
 connect(socket, SIGNAL(connected()), this, SLOT(socketConnected()));
 connect(socket, SIGNAL(disconnected()), this, SLOT(socketDisconnected()));
 connect(socket, SIGNAL(readyRead()), this, SLOT(socketReadyRead()));
 // Since this is only for testing purposes, we will connect the client to our test server,
 // which is located on the same computer.
 // If you're running the server on another computer,
 // you may change the IP address to a LAN or WAN address, depending on your need.
 socket->connectToHost("127.0.0.1", 8001);
 }
 else
 {
 QString name = ui->nameInput->text();
 socket->write("" + name.toUtf8() + " has left the chat room.");
 socket->disconnectFromHost();
 }

}

void MainWindow::socketConnected()
{
 qDebug() << "Connected to server.";
 printMessage("Connected to server.");
 QString name = ui->nameInput->text();
 socket->write("" + name.toUtf8() + " has joined the chat room.");
 ui->connectButton->setText("Disconnect");
 connectedToHost = true;
}

void MainWindow::socketDisconnected()
{
 qDebug() << "Disconnected from server.";
 printMessage("Disconnected from server.");
 ui->connectButton->setText("Connect");
 connectedToHost = false;
}

void MainWindow::socketReadyRead()
{
 ui->chatDisplay->append(socket->readAll());
}

void MainWindow::printMessage(QString message)
{
 ui->chatDisplay->append(message);
}

void MainWindow::on_sendButton_clicked()
{
 QString name = ui->nameInput->text();
 QString message = ui->messageInput->text();
 socket->write("" + name.toUtf8() + ": " + message.toUtf8());
 ui->messageInput->clear();
}

 Main.cpp

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#include "MainWindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
 QApplication a(argc, argv);

 MainWindow w;
 w.show();

 return a.exec();
}

构建成功后，将生成的QtInstantMessagingServer.exe以及QtInstantMessagingClient.exe置于.QtQt5.12.05.12.0mingw73_64in目录下（该目录下可以双击exe直接运行!）