Results 1 to 10 of 10

Thread: Reading from sockets in a multithreaded program

Hybrid View

Previous Post Previous Post   Next Post Next Post
  1. 4th April 2007, 20:43 #1
    moowy
    moowy is offline Intermediate user
    Join Date
    Aug 2006
    Posts
    83

    Default Re: Reading from sockets in a multithreaded program

    I have a problem with using Qt networking. I want to establish a connection between a server and clients. The client is using a chalkboard and is using server to send coordinates of the lines to draw to them. For the drawing part I am using Irrlecht (because the program is not going to be the chalboard (this is just for testing), but a real 3d environment.

    I have problem getting the communication to work. I would really appreciate if someone could look at the code (I attached) and please give me some clue.

    On the server side I have:
    Qt Code: 
    1. Server::Server(QObject *parent) : QTcpServer(parent)
    2. {
    3. 	/* maximum number of players */
    4. 	setMaxPendingConnections(8);
    5. 	m_connectedClients=-1; // none connected clients
    6. 	connect(this,SIGNAL(newConnection()),SLOT(newConnections()));
    7.  
    8. }
    9. void Server::send(int socket,int x1, int y1, int x2, int y2)
    10. {
    11. 	// I use qhash to keep information about all clients and socketDescriptors
    12. 	QHashIterator<int, Server_thread*> i(m_clients);
    13. 	while (i.hasNext()) {
    14. 		i.next();
    15. 		if(i.key() != socket) // don't send this to the client which send the info
    16. 			i.value()->send(x1,y1,x2,y2);
    17. 	} 
    18. }
    19.  
    20. /* accept incoming connections */
    21. void Server::newConnections()
    22. {
    23. 	while(hasPendingConnections()) {
    24. 		QTcpSocket *socket = nextPendingConnection();
    25. 		Server_thread *thread = new Server_thread(socket, this);
    26. 		// add the client and socketDescriptor
    27.                 m_clients[socket->socketDescriptor()] = thread;
    28. 		/* delete the thread that has finished */
    29. 		connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));
    30. 		thread->start();
    31. 	}
    32. }
    To copy to clipboard, switch view to plain text mode 
    The thread for clients...
    Qt Code: 
    1. Server_thread::Server_thread(QTcpSocket *socket, Server *parent)
    2.     : QThread(parent)
    3. {
    4. 	m_parent = parent;
    5. 	m_socket = socket;
    6. 	connect(this,SIGNAL(address(QString)),this,SLOT(new_connection(QString)));
    7. 	connect(m_socket,SIGNAL(readyRead()),this,SLOT(read()));
    8. 	m_socketDescriptor = m_socket->socketDescriptor();
    9.  
    10. 	emit address(m_socket->peerAddress().toString());
    11.  
    12. 	/* number of clients++ */
    13. 	m_parent->incNrClients();
    14.  
    15. 	nextBlockSize=0;
    16. }
    17.  
    18.  
    19. void Server_thread::run()
    20. {
    21. 	// just to keep the thread active...
    22. 	while(m_socket && m_socket->state() == QAbstractSocket::ConnectedState) {
    23.  
    24. 	}
    25.  
    26. 	m_socket->disconnectFromHost();
    27. 	m_socket->waitForDisconnected(1000);
    28. }
    29.  
    30. void Server_thread::read()
    31. {
    32. 	QDataStream in(m_socket);
    33. 	in.setVersion(QDataStream::Qt_4_2);
    34. 	/* read data */
    35. 	if(nextBlockSize==0) {
    36. 		if(m_socket->bytesAvailable() < sizeof(quint16))
    37. 			return;
    38.  
    39. 		in >> nextBlockSize;
    40. 	}
    41. 	if(m_socket->bytesAvailable() < nextBlockSize)
    42. 		return;
    43.  
    44. 	QString koordinate;
    45. 	int x1,y1,x2,y2;
    46.  
    47. 	in >> koordinate;
    48.  
    49. 	sscanf(koordinate.toStdString().c_str(),"%d %d %d %d",&x1,&y1,&x2,&y2);
    50.  
    51. 	m_parent->send(m_socketDescriptor,x1,y1,x2,y2);	
    52. }
    53.  
    54. void Server_thread::send(int x1, int y1, int x2, int y2)
    55. {
    56. 	QString string;
    57. 	string += QString(to_string<int>(x1).c_str());
    58. 	string += " ";
    59. 	string += QString(to_string<int>(y1).c_str());
    60. 	string += " ";
    61. 	string += QString(to_string<int>(x2).c_str());
    62. 	string += " ";
    63. 	string += QString(to_string<int>(y2).c_str());
    64.  
    65.  
    66. 	QByteArray block;
    67. 	QDataStream out(&block, QIODevice::WriteOnly);
    68. 	out.setVersion(QDataStream::Qt_4_2);
    69. 	out << (quint16)0;
    70. 	out << string;
    71. 	out.device()->seek(0);
    72. 	out << (quint16)(block.size() - sizeof(quint16));
    73.  
    74. 	m_socket->write(block);
    75.  
    76. }
    To copy to clipboard, switch view to plain text mode 

    On the client side I have:
    Qt Code: 
    1. using namespace irr;
    2. using namespace core;
    3. using namespace scene;
    4. using namespace video;
    5.  
    6. //event listener -> this works for sure
    7. class ChalkboardEventReceiver : public IEventReceiver
    8. {
    9. public:
    10.     ChalkboardEventReceiver(Client *c) 
    11.     : mouseDown(false), connection(NULL)
    12.     {
    13.         connection = c;
    14.     }
    15.  
    16.     bool OnEvent(SEvent event)
    17.     {
    18.         if(event.EventType == EET_MOUSE_INPUT_EVENT) {
    19.             if(event.MouseInput.Event == EMIE_LMOUSE_PRESSED_DOWN) {
    20.                 x = event.MouseInput.X;
    21.                 y = event.MouseInput.Y;
    22.                 mouseDown = true;
    23.  
    24.                 return true;
    25.             }
    26.             else if(event.MouseInput.Event == EMIE_LMOUSE_LEFT_UP) {
    27. 				connection->AddLineLocal(x, y, event.MouseInput.X, event.MouseInput.Y);
    28.                 connection->SendLineToServer(x, y, event.MouseInput.X, event.MouseInput.Y);
    29.                 mouseDown = false;
    30.  
    31.                 return true;
    32.             }
    33.             else if(mouseDown && event.MouseInput.Event == EMIE_MOUSE_MOVED) {
    34.                 connection->AddLineLocal(x, y, event.MouseInput.X, event.MouseInput.Y);
    35.                 connection->SendLineToServer(x, y, event.MouseInput.X, event.MouseInput.Y);
    36.                 x = event.MouseInput.X;
    37.                 y = event.MouseInput.Y;
    38.  
    39.                 return true;
    40.             }
    41.         }
    42.  
    43.         return false;
    44.     }
    45.  
    46.  
    47. protected:
    48.     s32 x, y;
    49.     bool mouseDown;
    50.     Client *connection;
    51. };
    52.  
    53. int main(int argc, char *argv[])
    54. {
    55. 	QApplication app(argc, argv);
    56.  
    57.         Client client;
    58. 	ChalkboardEventReceiver receiver(&client);
    59. 	client.init(&receiver);
    60.  
    61. 	app.connect(&app, SIGNAL(lastWindowClosed()), &app, SLOT(quit()));
    62. 	return app.exec();
    63.  
    64. }
    65.  
    66. Client::Client(QWidget *parent) : QWidget(parent)
    67. {
    68. 	connect(&m_socket, SIGNAL(readyRead()), this, SLOT(HandlePacket()));
    69. 	connect(&m_socket, SIGNAL(error(QAbstractSocket::SocketError)),
    70.              this, SLOT(displayError(QAbstractSocket::SocketError)));
    71.         m_socket.connectToHost("127.0.0.1",3210);
    72. 	nextBlockSize = 0;
    73. 	// Wait for the init() call
    74.     device = 0;
    75.     // Default 
    76.    driverType = irr::video::EDT_OPENGL;
    77. }
    78.  
    79. void Client::SendLineToServer(s32 x1, s32 y1, s32 x2, s32 y2)
    80. {
    81.  
    82. 	QString string;
    83. 	string += QString(to_string<int>(x1).c_str());
    84. 	string += " ";
    85. 	string += QString(to_string<int>(y1).c_str());
    86. 	string += " ";
    87. 	string += QString(to_string<int>(x2).c_str());
    88. 	string += " ";
    89. 	string += QString(to_string<int>(y2).c_str());
    90.  
    91. 	QByteArray block;
    92. 	QDataStream out(&block, QIODevice::WriteOnly);
    93. 	out.setVersion(QDataStream::Qt_4_2);
    94. 	out << (quint16)0;
    95. 	out << string;
    96. 	out.device()->seek(0);
    97.  
    98. 	//calculate the size of the block
    99. 	out << (quint16)(block.size() - sizeof(quint16));
    100.  
    101. 	m_socket.write(block);
    102. }
    103.  
    104. void Client::HandlePacket()
    105. {
    106. 	QDataStream in(&m_socket);
    107.     in.setVersion(QDataStream::Qt_4_2);
    108.  
    109. 	if (nextBlockSize == 0) {
    110. 		if (m_socket.bytesAvailable() < (int)sizeof(quint16))
    111. 			return;
    112.  
    113. 		in >> nextBlockSize;
    114. 	}
    115.  
    116. 	if (m_socket.bytesAvailable() < nextBlockSize)
    117. 		return;
    118.  
    119. 	QString string;
    120. 	in >> string;
    121.  
    122. 	s32 x1,y1,x2,y2;
    123. 	const char *str = string.toStdString().c_str();
    124. 	sscanf(str,"%d %d %d %d",&x1,&y1,&x2,&y2);
    125.  
    126. 	AddLineLocal(x1, y1, x2, y2);
    127. }
    To copy to clipboard, switch view to plain text mode 

    I'm sorry for posting so much code here (I attached the whole source code). I would really appreciate some help.
    Attached Files Attached Files
    Reply With Quote Reply With Quote
« Previous Thread | Next Thread »

Similar Threads

  1. QT MySQL
    By sabeeshcs in forum Newbie
    Replies: 6
    Last Post: 12th January 2007, 04:19
  2. Reading from TCP Socket crashes program
    By OnionRingOfDoom in forum Qt Programming
    Replies: 26
    Last Post: 27th January 2006, 19:32

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Forum Rules

Qt is a trademark of The Qt Company.