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Author Topic: TcpSockets, Selector, Listner, Frame Rate Dropping  (Read 3051 times)

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dixondean25

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TcpSockets, Selector, Listner, Frame Rate Dropping
« on: August 05, 2014, 02:50:37 pm »
I'm at the point in my game where I want to start doing networking to play with my friends. My server and client code is minimal, and they're not even sending or receiving from each other yet. For now, I'm controlling the environment by only allowing one client to connect, and I'm running the client and server on the same laptop.

The server/client code is run in a separate thread than all my game code. The thread first asks what the user is, a sever or a client, then it goes from there.

The problem is, once the client connects to the server, the server's game frame rate drops drastically, and only sometimes the client does too. But mostly just the server. I'm not sending anything back and forth yet, I only allow the client to connect to the server.

Right when I disconnect the client, the server then runs perfectly normal. Its frame rate only drops when connected.

Here is the entire code for the server and clients.
void runNet(void* UserData)
  {

          SoccerLevelsClass* obj = static_cast<SoccerLevelsClass*>(UserData);

          obj->netQuit=false;

          obj->netType = 0;

          cout<<"What are you? 0 for server, 1 for client : ";
         
          cin>>obj->netType; //store network type( 0 for sever, 1 for client)
         
          cout<<"\n";

          // start of server code
          if(obj->netType==0)
          {
                  // Create a socket to listen to new connections
                  sf::TcpListener listener;
                  listener.listen(2000);

                  // Create a list to store the future clients
                  std::vector<sf::TcpSocket*> clients;

                  // Create a selector
                  sf::SocketSelector selector;

                  // Add the listener to the selector
                  selector.add(listener);

                  listener.setBlocking(false);
                  // Endless loop that waits for new connections
                  while (obj->netQuit==false)
                  {
                         // cout<<"waiting.\n";

                          // Make the selector wait for data on any socket
                          if (selector.wait(sf::milliseconds(1)))
                          {
                                  cout<<"done waiting. listening.\n";

                                  // Test the listener
                                  if (selector.isReady(listener))
                                  {
                                          cout<<"trying to add client.\n";

                                          // The listener is ready: there is a pending connection
                                          sf::TcpSocket* client = new sf::TcpSocket;
                                          if (listener.accept(*client) == sf::Socket::Done)
                                          {
                                                  client->setBlocking(false);
                                                 
                                                  // Add the new client to the clients list
                                                  clients.push_back(client);

                                                  // Add the new client to the selector so that we will
                                                  // be notified when he sends something
                                                 
                                                  selector.add(*client);
                                                  cout<<"added client.\n";
                                          }
                                          else
                                          {
                                                  // Error, we won't get a new connection, delete the socket
                                                  delete client;
                                          }
                                  }
                                  else
                                  {
                                          cout<<"testing clients.\n";

                                          // The listener socket is not ready, test all other sockets (the clients)
                                          for (std::vector<sf::TcpSocket*>::iterator it = clients.begin(); it != clients.end(); ++it)
                                          {
                                                  sf::TcpSocket& client = **it;
                                                  if (selector.isReady(client))
                                                  {
                                                   /*
                                                          // The client has sent some data, we can receive it
                                                          sf::Packet packet;
                                                          packet << obj->playerOneStruct;
                                                          client.send(packet);
                                                          packet.clear();
                                                          if (client.receive(packet) == sf::Socket::Done)
                                                          {
                                                                 // ...
                                                          }
                                                   */

                                                  }
                                          }
                                  }
                          }
                  }
          }// end of server code

          // start of client code
          if(obj->netType==1)
          {
                  sf::IpAddress server;
                  do
                  {
                          std::cout << "Type the address or name of the server to connect to: ";
                          std::cin  >> server;
                  }
                  while (server == sf::IpAddress::None);


                  cout<<"here1\n";
                  sf::TcpSocket socket;

                  while(socket.connect(server,2000) != sf::Socket::Done)
                  {

                  }
                  cout<<"connected.\n";
                  socket.setBlocking(false);

                  while(obj->netQuit==false)
                  {
                   /*
                         sf::Packet packet;
                          sf::Socket::Status status = socket.receive(packet);
                          if (status == sf::Socket::Done)
                          {
                                  packet >> obj->playerOneStruct;
                                  cout<<"herh\n";
                          }
                          else if(status == sf::Socket::NotReady)
                          {
                                  cout<<"not ready.\n";
                          }
                          else if(status == sf::Socket::Disconnected)
                          {
                                  cout<<"disconnected.\n";
                          }
                          else if(status == sf::Socket::Error)
                          {
                                  cout<<"error.\n";
                          }
                         
                   */

                  }

          }// end of client code
  }// end of thread function

I commented out all the code I thought would cause my server to lag, but it's still lagging. I don't understand why it's causing my game to drop its frame rate, especially when it runs in a separate thread.

So here are my questions:

1. Is this code okay? Do you see anything that would make it lag the computer?

2.Do you think it's because I'm running the client and server on the same machine? Could that be the reason why the frame rate is dropping?

Thank You

binary1248

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Re: TcpSockets, Selector, Listner, Frame Rate Dropping
« Reply #1 on: August 05, 2014, 04:44:29 pm »
What you basically have in your server portion is this:
while (obj->netQuit==false)
{
        selector.wait(sf::milliseconds(1))

        // Other stuff that probably takes less than 1 millisecond
}
If you loop on a blocking call, the application will.... block a lot. I highly doubt that your other code requires more than 1 millisecond in total to run, so that call is what takes up almost all the time which makes the difference so prominent. Your server thread ends up effectively blocking for 99.999% of the time (and this blocking can have many manifestations from simple sleeping to busy waiting etc.), hence the "low frame rate" if you can even consider a frame rate for a thread that blocks that much...

If you remove the sf::milliseconds(1) and let the selector return immediately (default timeout value is sf::Time::Zero) you will see what I mean.

Also... you don't have to set your listener or client sockets to non-blocking if you are already using a selector. This can make sense in very advanced use cases, but in general it is not required.

If this wasn't the problem, then you will have to post more code. It is hard to tell from the code you provided whether this is a code-related issue or something completely different.
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dixondean25

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Re: TcpSockets, Selector, Listner, Frame Rate Dropping
« Reply #2 on: August 05, 2014, 05:21:09 pm »
If this wasn't the problem, then you will have to post more code. It is hard to tell from the code you provided whether this is a code-related issue or something completely different.

That is the entire server/client code.
hence the "low frame rate" if you can even consider a frame rate for a thread that blocks that much...

I'm not worried about the frame rate dropping in the server/client thread. The frame rate is dropping in the other thread that runs the game.

Which brings me to my next point. I ran some tests and it's only lagging because I'm running the the server and client on the same laptop, and it basically can't handle it.

While I'm here though, when you were talking about the wait time, did you mean i should leave it at the default value, or should I set a bigger time?

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Re: TcpSockets, Selector, Listner, Frame Rate Dropping
« Reply #3 on: August 05, 2014, 05:22:26 pm »
Quote
did you mean i should leave it at the default value

Yes.
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dixondean25

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Re: TcpSockets, Selector, Listner, Frame Rate Dropping
« Reply #4 on: August 05, 2014, 05:29:43 pm »
Alright thank you guys for replying, I appreciate it. I'm sorry to have wasted your time before checking everything.