测试环境

本文选用pc1作为客户端，pc2，以及一台虚拟机作为服务端。

• pc1,pc2(客户端）:
  
• 虚拟机（服务端)：
  

客户端

• 原理：客户端通过发送广播消息信息到ip:255.255.255.255(QHostAddress::Broadcast),局域网内的所有设备收到该消息回复客户端即可。客户端通过收到的回复统计当前有哪些设备在线。
• 获取到本地的IP，getLocalIP函数获取到过滤了虚拟机网卡以及本地回环网卡后的ip地址。
  

#include "udpclient.h"
#include <QDebug>
#include <QHostInfo>
#include <QNetworkInterface>
#include <iostream>

udpClient::udpClient(QObject *parent) : QObject(parent)
{
    QString localIp = getLocalIP();
    udpSocket = new QUdpSocket;
    udpSocket->bind(QHostAddress(localIp),2001);
    connect(udpSocket,&QUdpSocket::readyRead,this,&udpClient::processData);

}

QString udpClient::getLocalIP() {
    QList<QNetworkInterface> interfaces = QNetworkInterface::allInterfaces();
    foreach (const QNetworkInterface &interface, interfaces) {
       QList<QNetworkAddressEntry> entries = interface.addressEntries();
       qDebug()<<"name:"<<interface.humanReadableName()<<endl;
       if(interface.humanReadableName().contains("Loopback") ||
          interface.humanReadableName().contains("VMware Network Adapter"))
       {
           continue;
       }
       foreach (const QNetworkAddressEntry &entry, entries) {
           if (entry.ip().protocol() == QAbstractSocket::IPv4Protocol) {
               qDebug() << "Local IP Address: " << entry.ip().toString()<< endl;
           }
       }
    }
    return QString();
}

udpClient::~udpClient()
{
    if(udpSocket)
    {
        delete udpSocket;
    }
}

void udpClient::sendBroadCast()
{
    QByteArray datagram = "Device Discovery";
    udpSocket->writeDatagram(datagram,QHostAddress::Broadcast,8888);
}


void udpClient::processData()
{
    while(udpSocket->hasPendingDatagrams())
    {
        QByteArray datagram;
        datagram.resize(udpSocket->pendingDatagramSize());
        QHostAddress sender;
        quint16 senderPort;

        udpSocket->readDatagram(datagram.data(), datagram.size(), &sender, &senderPort);
        qDebug() << "Received response from: " << sender.toString()<<"port:"<<senderPort << endl;
    }
}

服务端

#include "udpserver.h"
#include <iostream>


udpServer::udpServer(QObject *parent) : QObject(parent)
{
    udpSocket = new QUdpSocket(this);
    udpSocket->bind(QHostAddress::Any, 8888);

    connect(udpSocket, &QUdpSocket::readyRead, this, &udpServer::processPendingDatagrams);

}

void udpServer::processPendingDatagrams()
{
    while (udpSocket->hasPendingDatagrams()) {
        QByteArray datagram;
        datagram.resize(udpSocket->pendingDatagramSize());
        QHostAddress sender;
        quint16 senderPort;

        udpSocket->readDatagram(datagram.data(), datagram.size(), &sender, &senderPort);
        std::cout << "Received discovery message: " << datagram.data() << std::endl;

        QByteArray response = "Device Found";
        udpSocket->writeDatagram(response, sender, senderPort);
    }
}

输出效果