我正在实现一个基于 Windows 的 Web 服务器，它使用WinSock2处理来自客户端的多个特定 HTTP 请求。我有一门课来启动和停止我的服务器。它看起来像这样：
class CMyServer
{
// Not related to this question methods and variables here
// ...
public:
SOCKET m_serverSocket;
TLM_ERROR Start();
TLM_ERROR Stop();
static DWORD WINAPI ProcessRequest(LPVOID pInstance);
static DWORD WINAPI Run(LPVOID pInstance);
}
whereTLM_ERROR是我的服务器错误枚举的类型定义。
bool CMyServer::Start()方法启动服务器，在配置的端口上创建一个套接字侦听并创建一个单独的线程DWORD CMyServer::Run(LPVOID)来接受传入连接，如下所述：
// Creating a socket
m_serverSocket = ::socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (m_serverSocket == INVALID_SOCKET)
return TLM_ERROR_CANNOT_CREATE_SOCKET;
// Socket address
sockaddr_in serverSocketAddr;
serverSocketAddr.sin_family = AF_INET; // address format is host and port number
serverSocketAddr.sin_addr.S_un.S_addr = inet_addr(m_strHost.c_str()); // specifying host
serverSocketAddr.sin_port = htons(m_nPort); // specifying port number
// Binding the socket
if (::bind(m_serverSocket, (SOCKADDR*)&serverSocketAddr, sizeof(serverSocketAddr)) == SOCKET_ERROR)
{
// Error during binding the socket
::closesocket(m_serverSocket);
m_serverSocket = NULL;
return TLM_ERROR_CANNOT_BIND_SOCKET;
}
// Starting to listen to requests
int nBacklog = 20;
if (::listen(m_serverSocket, nBacklog) == SOCKET_ERROR)
{
// Error listening on socket
::closesocket(m_serverSocket);
m_serverSocket = NULL;
return TLM_ERROR_CANNOT_LISTEN;
}
// Further initialization here...
// ...
// Creating server's main thread
m_hManagerThread = ::CreateThread(NULL, 0, CTiledLayersManager::Run, (LPVOID)this, NULL, NULL);
I use ::accept(...) to wait for incoming client connections in CMyServer::Run(LPVOID), and after new connection has been accepted I create a separate thread CMyServer::ProcessRequest(LPVOID) to receive a data from a client and send a response passing the socket returned by ::accept(...) as part of thread function's argument:
DWORD CMyServer::Run(LPVOID pInstance)
{
CMyServer* pTLM = (CMyServer*)pInstance;
// Initialization here...
// ...
bool bContinueRun = true;
while (bContinueRun)
{
// Waiting for a client to connect
SOCKADDR clientSocketAddr; // structure to store socket's address
int nClientSocketSize = sizeof(clientSocketAddr); // defining structure's length
ZeroMemory(&clientSocketAddr, nClientSocketSize); // cleaning the structure
SOCKET connectionSocket = ::accept(pTLM->m_serverSocket, &clientSocketAddr, &nClientSocketSize); // waiting for client's request
if (connectionSocket != INVALID_SOCKET)
{
if (bContinueRun)
{
// Running a separate thread to handle this request
REQUEST_CONTEXT rc;
rc.pTLM = pTLM;
rc.connectionSocket = connectionSocket;
HANDLE hRequestThread = ::CreateThread(NULL, 0, CTiledLayersManager::ProcessRequest, (LPVOID)&rc, CREATE_SUSPENDED, NULL);
// Storing created thread's handle to be able to close it later
// ...
// Starting suspended thread
::ResumeThread(hRequestThread);
}
}
// Checking whether thread is signaled to stop...
// ...
}
// Waiting for all child threads to over...
// ...
}
Testing this implementation manually gives me the desired results. But when I send multiple requests generated by JMeter I can see that some of them are not handled properly by DWORD CMyServer::ProcessRequest(LPVOID). Looking at log file created by ProcessRequest I determine 10038 WinSock error code (meaning that ::recv call was tried on nonsocket), 10053 error code (Software caused connection abort) or even 10058 error code (Cannot send after socket shutdown). But the 10038th error occurs more often than others mentioned.
It looks like a socket was closed somehow but I close it only after ::recv and ::send have been called in ProcessRequest. I also thought that it can be an issue related to using ::CreateThread instead of ::_beginthreadex but as I can get it could only lead to memory leaks. I don't have any memory leaks detected by the method described here so I have doubts that it is the reason. All the more, ::CreateThread returns a handle that can be used in ::WaitForMultipleObjects to wait for threads to be over, and I need it to stop my server properly.
Could these errors occur due to a client doesn't want to wait for response anymore? I am out of ideas, and I will thank you if you tell me what I am missing or doing/understanding wrong. By the way, both my server and JMeter run on the localhost.
Finally, here is my implementation of ProcessRequest method:
DWORD CMyServer::ProcessRequest(LPVOID pInstance)
{
REQUEST_CONTEXT* pRC = (REQUEST_CONTEXT*)pInstance;
CMyServer* pTLM = pRC->pTLM;
SOCKET connectionSocket = pRC->connectionSocket;
// Retrieving client's request
const DWORD dwBuffLen = 1 << 15;
char buffer[dwBuffLen];
ZeroMemory(buffer, sizeof(buffer));
if (::recv(connectionSocket, buffer, sizeof(buffer), NULL) == SOCKET_ERROR)
{
stringStream ss;
ss << "Unable to receive client's request with the following error code " << ::WSAGetLastError() << ".";
pTLM->Log(ss.str(), TLM_LOG_TYPE_ERROR);
::SetEvent(pTLM->m_hRequestCompleteEvent);
return 0;
}
string str = "HTTP/1.1 200 OK\nContent-Type: text/plain\n\nHello World!";
if (::send(connectionSocket, str.c_str(), str.length(), 0) == SOCKET_ERROR)
{
stringStream ss;
ss << "Unable to send response to client with the following error code " << ::WSAGetLastError() << ".";
pTLM->Log(ss.str(), TLM_LOG_TYPE_ERROR);
::SetEvent(pTLM->m_hRequestCompleteEvent);
return 0;
}
::closesocket(connectionSocket);
connectionSocket = NULL;
pTLM->Log(string("Request has been successfully handled."));
::SetEvent(pTLM->m_hRequestCompleteEvent);
return 0;
}