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How to thread a class - Client Server Program

Steve K. · 2013-11-28T12:33:42

So I've looked around with Bing search as to how to thread a class. I see lot's of nice wrappers with lots of heavy duty pointer stashing and caching and said there's got to be an easier way. Well here it is, what you all have been waiting for ... threading a class!! It's so simple your just going to want to do it in every class you write. I'll just put my server class here and comment where the thread dependent items are. (btw, it's still a work-in-process but it does get a listen server and a client connection with data being passed) The includes are just windows stuff and some simple buffers and not necessary to discuss. Header #pragma once #include "includes.h" #include "ChatPacket.h" class Server { public: Server(void); ~Server(void); // some normal methods short Server::Initialize(short port); short Server::Disconnect(); short Server::Send(); void Server::Listening(); // these two methods are going to be the threads // notice the use of static and the (void* t) parameter static void Server::Accepting(void* t); static void Server::Receiver(void* t); char buffer[VERY_LARGE_STRING]; private: WSADATA wsaData; SOCKET listenSocket; SOCKET clientSocket; // some Booleans to keep track of which threads are active bool listenerIsActive; bool accepterIsActive; bool receiverIsActive; int receiveLength; int sendLength; // thread ID variables uintptr_t listenThread; uintptr_t acceptThread; uintptr_t receiveThread; uintptr_t sendThread; struct addrinfo *result, *ptr, hints; ChatPacket* chatPacket; }; Methods #include "Server.h" Server::Server(void) { memset(this, 0x00, sizeof(Server)); } Server::~Server(void) { if (receiverIsActive) { //set the Boolean to false so the thread will stop receiverIsActive = false; // wait for 1 second so the thread can stop Sleep(1000); } if(accepterIsActive) { // and again accepterIsActive = false; Sleep(1000); closesocket(clientSocket); clientSocket = 0; } if(listenerIsActive) { // and again for this one listenerIsActive = false; Sleep(1000); closesocket(listenSocket); listenSocket = 0; } WSACleanup(); } short Server::Initialize(short port) { // initialize winsock r = WSAStartup(MAKEWORD(2, 2), &wsaData); if (FAILED(r)) { PrintDebugString("%s", DXGetErrorString(r)); return 0; } memset(&hints, 0x00, sizeof(hints)); hints.ai_family = AF_INET; hints.ai_socktype = SOCK_STREAM; hints.ai_protocol = IPPROTO_TCP; hints.ai_flags = AI_PASSIVE; // resolve this servers address and port // port has to be a character string ... who'da thought that! char p[6]; sprintf(p, "%i", port); r = getaddrinfo(NULL, p, &hints, &result); if (FAILED(r)) { PrintDebugString("%s", DXGetErrorString(r)); WSACleanup(); return 0; } // create a SOCKET for this server listenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol); if (listenSocket == INVALID_SOCKET) { freeaddrinfo(result); WSACleanup(); listenSocket = 0; return 0; } // bind the TCP listening socket r = bind(listenSocket, result->ai_addr, (int)result->ai_addrlen); if (r == INVALID_SOCKET) { freeaddrinfo(result); closesocket(listenSocket); WSACleanup(); listenSocket = 0; return 0; } freeaddrinfo(result); // start the listen server for connect requests Server::Listening(); // start the accepting thread for connect requests acceptThread = _beginthread(&Server::Accepting, 0, this); // start the receiving thread for receiving data receiveThread = _beginthread(&Server::Receiver, 0, this); return 1; } void Server::Listening() { // thought this might need to be threaded but turns out it doesn't // so toss the boolean out listenerIsActive = true; r = listen(listenSocket, SOMAXCONN); if (r == INVALID_SOCKET) { closesocket(listenSocket); WSACleanup(); listenSocket = 0; } } void Server::Accepting(void* t) { // using this as a thread must cast the this pointer // to something usable Server* s = (Server*)t; // set the Boolean to true so we know the thread is running s->accepterIsActive = true; // infinite loop until the Boolean is changed to false somewhere else in the class // i.e the deconstructor or the disconnect method while(s->accepterIsActive) { s->clientSocket = accept(s->listenSocket, 0, 0); if (s->clientSocket == INVALID_SOCKET) { closesocket(s->clientSocket); WSACleanup(); s->clientSocket = 0; return; } // needed a spot to put a stopper for my debugger if (s->clientSocket > 0) { int zz = 0; zz++; // I put the stopper on this line } } } short Server::Send() { // note-to-self don't use strlen(buffer) as there could be 0x00 somewhere in the buffer // and will not send the entire buffer if there is sendLength = send(clientSocket, buffer, strlen(buffer), 0); if (sendLength == SOCKET_ERROR) { PrintDebugString("Server::Send failed with error: %d", WSAGetLastError()); closesocket(clientSocket); WSACleanup(); return 0; } return 1; } void Server::Receiver(void* t) { Server* s = (Server*)t; // set the Boolean to show the thread is running s->receiverIsActive = true; // loop until this Boolean is false while(s->receiverIsActive) { if (s->clientSocket > 0) { memset(s->buffer, 0x00, VERY_LARGE_STRING); s->receiveLength = recv(s->clientSocket, s->buffer, VERY_LARGE_STRING, 0); if (s->receiveLength > 0) { // doing my client receive logic here PrintDebugString("Server::Bytes received: %d", s->receiveLength); if ((s->buffer[0] == 'C') && (s->buffer[1] == 'H')) { s->chatPacket = new ChatPacket(); memcpy(s->chatPacket, s->buffer, s->receiveLength); PrintDebugString("Server::CH: %s", s->chatPacket->message); delete s->chatPacket; s->chatPacket = 0; } memset(s->buffer, 0x00, VERY_LARGE_STRING); } else if (s->receiveLength == 0) { PrintDebugString("Server::No Data..."); } else { PrintDebugString("Server::Recv failed: %d", WSAGetLastError()); closesocket(s->clientSocket); WSACleanup(); s->receiverIsActive = false; return; } } } } short Server::Disconnect() { receiverIsActive = false; if(accepterIsActive) { accepterIsActive = false; Sleep(1000); closesocket(clientSocket); clientSocket = 0; } if(listenerIsActive) { listenerIsActive = false; Sleep(1000); closesocket(listenSocket); listenSocket = 0; } WSACleanup(); return 1; } And that's all there is to threading with a class. Don't bother with starting the thread outside of the class. Too much chaos in doing that. Simply call a method within the class to start the threading or do it in the class on its own with the constructor. One final thought is that this server is set up to connect only one client so don't just cut and paste and assume its going to handle multiple clients (hint: s->clientSocket[x] or maybe put them in a link list?) Microsoft's MSDN Links for Client Server Programming with Winsock Getting Started With Winsock Complete Server Code Complete Client Code

General and Gameplay Programming Programming

Started by codejockey November 25, 2013 04:46 AM

11 comments, last by BitMaster 10 years, 4 months ago

King Mir

2,506

November 28, 2013 01:34 AM

This is getting annoying. I only posted this because it shows how you can define the methods in a class to be threaded. If you want it to be professionally used then I suggest doing all the changes that all these brilliant people pointed out to make it universally acceptable in the C++ programming community. For me, it works, it does what I need, and isn't that actually what is important. btw I wouldn't work anywhere that has C++ as its main programming language. Get current with some managed code such as C# XNA or java.

But the code doesn't define methods to be threaded. It works on your particular machine, on your particular compiler settings, for the tests you did on it, but it's not correct code. Sharing memory without synchronization primitives is undefined behavior in C++, also called "catch fire semantics" because the code is legally allowed by the C++ standard to do anything including make your computer catch fire. Furthermore, this code is the worst kind of erroneous behavior, because it works most of the time, and doesn't give an easy to trace error when it doesn't, making the errors very hard to track down.

TheComet

3,927

November 28, 2013 11:12 AM

If you know assembler then you'll know this is fine:

memset(this, 0x00, sizeof(Server));

It has nothing to do with assembler. And no, that's the most atrocious, evil piece of code I've ever seen and belongs in the "Coding Horrors" section of this forum.

The correct thing to do is use an initialiser list in the constructor:


Server::Server() :
    listenerIsActive( false ),
    accepterIsActive( false ),
    receiverIsActive( false ),
    receiveLength( 0 ),
    sendLength( 0 )
    /* -- etc -- */
{
}

"I would try to find halo source code by bungie best fps engine ever created, u see why call of duty loses speed due to its detail." -- GettingNifty

BitMaster

8,652

November 28, 2013 12:33 PM

I wouldn't call it just that. For example, by adding the simple line

static_assert(std::is_pod<Server>::value);

would probably make it safe. I still wouldn't do it myself, but the compiler should scream at you instead of silently setting fire to the system.

My problem was less with the memset as such as more with the complete thoughtlessness and ignorance in putting it there. If you absolutely have to put something like that in there, at least comment the inherent dangers properly. If possible (not without C++11 support) also add compile time check.

How to thread a class - Client Server Program

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