C++ multithread HTTP Server - recv() hangs up after first sending first response - c++

Question

I'm trying to build a multithread HTTP server using C++ and winsock2.h and sys/socket.h.However, after sending response successfully to first request, accept() function captures other requests and sends through thread pool but those threads hangs up in recv() function so function can never capture data from socket.Here is my code.
void HTTPServer::init()
{
#ifdef _WIN32
WSADATA wsaData;
WSAStartup(0x202,&wsaData);
if((mSock = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP)) == INVALID_SOCKET)
#else
if((mSock = socket(AF_INET,SOCK_STREAM,0)) < 0)
#endif
{
std::cout << "Error while initilazing socket\n";
}
mServerAddr.sin_family = AF_INET;
mServerAddr.sin_port = htons(mPort);
#ifdef _WIN32
mServerAddr.sin_addr.S_un.S_addr = INADDR_ANY;
#else
mServerAddr.sin_addr.S_addr = INADDR_ANY;
#endif
if(bind(mSock, (struct sockaddr*) &mServerAddr, sizeof(mServerAddr)) < 0)
{
std::cout << "Error while binding socket\n";
}
if(listen(mSock, SOMAXCONN))
{
std::cout << "Error while listening socket\n";
}
}
void HTTPServer::fRun()
{
ThreadPool* tPool = new ThreadPool(10);
while(1)
{
int size = sizeof(mClientAddr);
#ifdef _WIN32
if((mAcceptSocket = accept(mSock,(struct sockaddr*) &mClientAddr,&size)) == INVALID_SOCKET)
#else
if((mAcceptSocket = accept(mSock,(struct sockaddr*) &mClientAddr,&size))) < 0)
#endif
{
std::cout << "Error while initilazing accept socket\n";
}
std::cout << "Socket Sent " << mAcceptSocket << std::endl;
tPool->enqueue([&] { this->fOnRequest(mAcceptSocket); });
}
delete tPool;
}
void HTTPServer::fOnRequest(uint64_t socket)
{
const string reqData = fRecieveNext(mAcceptSocket);
const HTTPResponse res = fProcessRequest(reqData);
fSendResponse(res,socket);
std::cout << "Done";
}
const string HTTPServer::fRecieveNext(uint64_t socket)
{
int64_t recieveLength = 0,totalRecieved = 0;
int64_t recieveLengthBeforeBody = -1;
int contentLength = 0;
string rawData;
while(1)
{
memset(mBuffer,'\0',8192);
if((recieveLength = recv(socket,mBuffer,8192, 0)) == SOCKET_ERROR)
{
std::cout << "Error while receiving data from socket\n";
#ifdef _WIN32
std::cout << WSAGetLastError() << std::endl;
#endif
break;
}
if(recieveLength == 0)
break;
totalRecieved += recieveLength;
rawData += string(mBuffer,recieveLength);
if(totalRecieved > 32)
{
if(rawData.find("Content-Length") == string::npos && contentLength == 0)
break;
else
{
if(contentLength == 0)
{
auto pos = rawData.find("Content-Length:");
auto lengthStr = rawData.substr(pos + 16, rawData.find_first_of("\r",pos) - pos - 16);
contentLength = std::stoi(lengthStr);
}
if(rawData.find("\r\n\r\n") != string::npos && recieveLengthBeforeBody == -1)
{
recieveLengthBeforeBody = rawData.find("\r\n\r\n") + 4;
}
if(totalRecieved >= contentLength + recieveLengthBeforeBody)
break;
}
}
}
return rawData;
}
void HTTPServer::fSendResponse(const HTTPResponse& response,const uint64_t socket)
{
string resStr = response.fSerializeResponse();
size_t sent = 0,totalSent = 0;
char* buffer = &(resStr[0]);
while(totalSent < resStr.length())
{
if((sent = send(socket, buffer, resStr.length() - totalSent,0)) < 0)
{
std::cout << "Error while sending response" << std::endl;
}
buffer += sent;
totalSent += sent;
}
delete &response;
#ifdef _WIN32
if(shutdown(socket, SD_BOTH) == SOCKET_ERROR)
{
std::cout << "Error while closing socket" << std::endl;
std::cout << WSAGetLastError() << std::endl;
};
if(closesocket(socket) == SOCKET_ERROR)
{
std::cout << "Error while closing socket" << std::endl;
std::cout << WSAGetLastError() << std::endl;
};
#else
if(shutdown(socket, SHUT_RDWR) < 0)
{
std::cout << "Error while closing socket" << std::endl;
};
if(close(socket) < 0)
{
std::cout << "Error while closing socket" << std::endl;
};
#endif
}

Answer 1

It looks like you are expecting to receive a TCP message all in one recv. TCP doesnt work like that. Tcp is a stream protocol, a message sent to you can be broken into multiple chunks. TCP only guarantees that the bytes will arrive once and in the correct order.
That would make you get out of sync with the input