peermanager.cpp Example File

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 #include <QtNetwork>

 #include "client.h"
 #include "connection.h"
 #include "peermanager.h"

 static const qint32 BroadcastInterval = 2000;
 static const unsigned broadcastPort = 45000;

 PeerManager::PeerManager(Client *client)
     : QObject(client)
 {
     this->client = client;

     static const char *envVariables[] = {
         "USERNAME", "USER", "USERDOMAIN", "HOSTNAME", "DOMAINNAME"
     };

     for (const char *varname : envVariables) {
         username = qEnvironmentVariable(varname);
         if (!username.isNull())
             break;
     }

     if (username.isEmpty())
         username = "unknown";

     updateAddresses();
     serverPort = 0;

     broadcastSocket.bind(QHostAddress::Any, broadcastPort, QUdpSocket::ShareAddress
                          | QUdpSocket::ReuseAddressHint);
     connect(&broadcastSocket, SIGNAL(readyRead()),
             this, SLOT(readBroadcastDatagram()));

     broadcastTimer.setInterval(BroadcastInterval);
     connect(&broadcastTimer, SIGNAL(timeout()),
             this, SLOT(sendBroadcastDatagram()));
 }

 void PeerManager::setServerPort(int port)
 {
     serverPort = port;
 }

 QString PeerManager::userName() const
 {
     return username;
 }

 void PeerManager::startBroadcasting()
 {
     broadcastTimer.start();
 }

 bool PeerManager::isLocalHostAddress(const QHostAddress &address)
 {
     foreach (QHostAddress localAddress, ipAddresses) {
         if (address.isEqual(localAddress))
             return true;
     }
     return false;
 }

 void PeerManager::sendBroadcastDatagram()
 {
     QByteArray datagram;
     {
         QCborStreamWriter writer(&datagram);
         writer.startArray(2);
         writer.append(username);
         writer.append(serverPort);
         writer.endArray();
     }

     bool validBroadcastAddresses = true;
     foreach (QHostAddress address, broadcastAddresses) {
         if (broadcastSocket.writeDatagram(datagram, address,
                                           broadcastPort) == -1)
             validBroadcastAddresses = false;
     }

     if (!validBroadcastAddresses)
         updateAddresses();
 }

 void PeerManager::readBroadcastDatagram()
 {
     while (broadcastSocket.hasPendingDatagrams()) {
         QHostAddress senderIp;
         quint16 senderPort;
         QByteArray datagram;
         datagram.resize(broadcastSocket.pendingDatagramSize());
         if (broadcastSocket.readDatagram(datagram.data(), datagram.size(),
                                          &senderIp, &senderPort) == -1)
             continue;

         int senderServerPort;
         {
             // decode the datagram
             QCborStreamReader reader(datagram);
             if (reader.lastError() != QCborError::NoError || !reader.isArray())
                 continue;
             if (!reader.isLengthKnown() || reader.length() != 2)
                 continue;

             reader.enterContainer();
             if (reader.lastError() != QCborError::NoError || !reader.isString())
                 continue;
             while (reader.readString().status == QCborStreamReader::Ok) {
                 // we don't actually need the username right now
             }

             if (reader.lastError() != QCborError::NoError || !reader.isUnsignedInteger())
                 continue;
             senderServerPort = reader.toInteger();
         }

         if (isLocalHostAddress(senderIp) && senderServerPort == serverPort)
             continue;

         if (!client->hasConnection(senderIp)) {
             Connection *connection = new Connection(this);
             emit newConnection(connection);
             connection->connectToHost(senderIp, senderServerPort);
         }
     }
 }

 void PeerManager::updateAddresses()
 {
     broadcastAddresses.clear();
     ipAddresses.clear();
     foreach (QNetworkInterface interface, QNetworkInterface::allInterfaces()) {
         foreach (QNetworkAddressEntry entry, interface.addressEntries()) {
             QHostAddress broadcastAddress = entry.broadcast();
             if (broadcastAddress != QHostAddress::Null && entry.ip() != QHostAddress::LocalHost) {
                 broadcastAddresses << broadcastAddress;
                 ipAddresses << entry.ip();
             }
         }
     }
 }