// Module Name: asyncselect.cpp
//
// Description:
//
// This sample illustrates how to develop a simple echo server Winsock
// application using the WSAAsyncSelect() I/O model. This sample is
// implemented as a console-style application (to reduce the programming
// complexity of writing a real Windows application) and simply prints
// messages when connections are established and removed from the server.
// The application listens for TCP connections on port 5150 and accepts them
// as they arrive. When this application receives data from a client, it
// simply echos (this is why we call it an echo server) the data back in
// it's original form until the client closes the connection.
//
// Since the WSAAsyncSelect I/O model requires an application to manage
// window messages when network event occur, this application creates
// a window for the I/O model only. The window stays hidden during the
// entire execution of this application.
//
// Compile:
//
// cl -o asyncselect asyncselect.cpp ws2_32.lib user32.lib gdi32.lib
//
// Command Line Options:
//
// asyncselect.exe
//
// Note: There are no command line options for this sample.
#include <winsock2.h>
#include <windows.h>
#include <stdio.h>
#include <conio.h>
#define PORT 5150
#define DATA_BUFSIZE 8192
typedef struct _SOCKET_INFORMATION {
BOOL RecvPosted;
CHAR Buffer[DATA_BUFSIZE];
WSABUF DataBuf;
SOCKET Socket;
DWORD BytesSEND;
DWORD BytesRECV;
_SOCKET_INFORMATION *Next;
} SOCKET_INFORMATION, * LPSOCKET_INFORMATION;
#define WM_SOCKET (WM_USER + 1)
void CreateSocketInformation(SOCKET s);
LPSOCKET_INFORMATION GetSocketInformation(SOCKET s);
void FreeSocketInformation(SOCKET s);
HWND MakeWorkerWindow(void);
LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
LPSOCKET_INFORMATION SocketInfoList;
void main(void)
{
MSG msg;
DWORD Ret;
SOCKET Listen;
SOCKADDR_IN InternetAddr;
HWND Window;
WSADATA wsaData;
if ((Window = MakeWorkerWindow()) == NULL)
return;
// Prepare echo server
if ((Ret = WSAStartup(0x0202, &wsaData)) != 0)
{
printf("WSAStartup failed with error %d\n", Ret);
return;
}
if ((Listen = socket (PF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET)
{
printf("socket() failed with error %d\n", WSAGetLastError());
return;
}
WSAAsyncSelect(Listen, Window, WM_SOCKET, FD_ACCEPT|FD_CLOSE);
InternetAddr.sin_family = AF_INET;
InternetAddr.sin_addr.s_addr = htonl(INADDR_ANY);
InternetAddr.sin_port = htons(PORT);
if (bind(Listen, (PSOCKADDR) &InternetAddr, sizeof(InternetAddr)) == SOCKET_ERROR)
{
printf("bind() failed with error %d\n", WSAGetLastError());
return;
}
if (listen(Listen, 5))
{
printf("listen() failed with error %d\n", WSAGetLastError());
return;
}
// Translate and dispatch window messages for the application thread
while(Ret = GetMessage(&msg, NULL, 0, 0))
{
if (Ret == -1)
{
printf("GetMessage() failed with error %d\n", GetLastError());
return;
}
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
SOCKET Accept;
LPSOCKET_INFORMATION SocketInfo;
DWORD RecvBytes, SendBytes;
DWORD Flags;
if (uMsg == WM_SOCKET)
{
if (WSAGETSELECTERROR(lParam))
{
printf("Socket failed with error %d\n", WSAGETSELECTERROR(lParam));
FreeSocketInformation(wParam);
}
else
{
switch(WSAGETSELECTEVENT(lParam))
{
case FD_ACCEPT:
if ((Accept = accept(wParam, NULL, NULL)) == INVALID_SOCKET)
{
printf("accept() failed with error %d\n", WSAGetLastError());
break;
}
// Create a socket information structure to associate with the
// socket for processing I/O.
CreateSocketInformation(Accept);
printf("Socket number %d connected\n", Accept);
WSAAsyncSelect(Accept, hwnd, WM_SOCKET, FD_READ|FD_WRITE|FD_CLOSE);
break;
case FD_READ:
SocketInfo = GetSocketInformation(wParam);
// Read data only if the receive buffer is empty.
if (SocketInfo->BytesRECV != 0)
{
SocketInfo->RecvPosted = TRUE;
return 0;
}
else
{
SocketInfo->DataBuf.buf = SocketInfo->Buffer;
SocketInfo->DataBuf.len = DATA_BUFSIZE;
Flags = 0;
if (WSARecv(SocketInfo->Socket, &(SocketInfo->DataBuf), 1, &RecvBytes,
&Flags, NULL, NULL) == SOCKET_ERROR)
{
if (WSAGetLastError() != WSAEWOULDBLOCK)
{
printf("WSARecv() failed with error %d\n", WSAGetLastError());
FreeSocketInformation(wParam);
return 0;
}
}
else // No error so update the byte count
{
SocketInfo->BytesRECV = RecvBytes;
}
}
// DO NOT BREAK HERE SINCE WE GOT A SUCCESSFUL RECV. Go ahead
// and begin writing data to the client.
case FD_WRITE:
SocketInfo = GetSocketInformation(wParam);
if (SocketInfo->BytesRECV > SocketInfo->BytesSEND)
{
SocketInfo->DataBuf.buf = SocketInfo->Buffer + SocketInfo->BytesSEND;
SocketInfo->DataBuf.len = SocketInfo->BytesRECV - SocketInfo->BytesSEND;
if (WSASend(SocketInfo->Socket, &(SocketInfo->DataBuf), 1, &SendBytes, 0,
NULL, NULL) == SOCKET_ERROR)
{
if (WSAGetLastError() != WSAEWOULDBLOCK)
{
printf("WSASend() failed with error %d\n", WSAGetLastError());
FreeSocketInformation(wParam);
return 0;
}
}
else // No error so update the byte count
{
SocketInfo->BytesSEND += SendBytes;
}
}
if (SocketInfo->BytesSEND == SocketInfo->BytesRECV)
{
SocketInfo->BytesSEND = 0;
SocketInfo->BytesRECV = 0;
// If a RECV occurred during our SENDs then we need to post an FD_READ
// notification on the socket.
if (SocketInfo->RecvPosted == TRUE)
{
SocketInfo->RecvPosted = FALSE;
PostMessage(hwnd, WM_SOCKET, wParam, FD_READ);
}
}
break;
case FD_CLOSE:
printf("Closing socket %d\n", wParam);
FreeSocketInformation(wParam);
break;
}
}
return 0;
}
return DefWindowProc(hwnd, uMsg, wParam, lParam);
}
void CreateSocketInformation(SOCKET s)
{
LPSOCKET_INFORMATION SI;
if ((SI = (LPSOCKET_INFORMATION) GlobalAlloc(GPTR,
sizeof(SOCKET_INFORMATION))) == NULL)
{
printf("GlobalAlloc() failed with error %d\n", GetLastError());
return;
}
// Prepare SocketInfo structure for use.
SI->Socket = s;
SI->RecvPosted = FALSE;
SI->BytesSEND = 0;
SI->BytesRECV = 0;
SI->Next = SocketInfoList;
SocketInfoList = SI;
}
LPSOCKET_INFORMATION GetSocketInformation(SOCKET s)
{
SOCKET_INFORMATION *SI = SocketInfoList;
while(SI)
{
if (SI->Socket == s)
return SI;
SI = SI->Next;
}
return NULL;
}
void FreeSocketInformation(SOCKET s)
{
SOCKET_INFORMATION *SI = SocketInfoList;
SOCKET_INFORMATION *PrevSI = NULL;
while(SI)
{
if (SI->Socket == s)
{
if (PrevSI)
PrevSI->Next = SI->Next;
else
SocketInfoList = SI->Next;
closesocket(SI->Socket);
GlobalFree(SI);
return;
}
PrevSI = SI;
SI = SI->Next;
}
}
HWND MakeWorkerWindow(void)
{
WNDCLASS wndclass;
CHAR *ProviderClass = "AsyncSelect";
HWND Window;
wndclass.style = CS_HREDRAW | CS_VREDRAW;
wndclass.lpfnWndProc = (WNDPROC)WindowProc;
wndclass.cbClsExtra = 0;
wndclass.cbWndExtra = 0;
wndclass.hInstance = NULL;
wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
wndclass.hbrBackground = (HBRUSH) GetStockObject(WHITE_BRUSH);
wndclass.lpszMenuName = NULL;
wndclass.lpszClassName = ProviderClass;
if (RegisterClass(&wndclass) == 0)
{
printf("RegisterClass() failed with error %d\n", GetLastError());
return NULL;
}
// Create a window.
if ((Window = CreateWindow(
ProviderClass,
"",
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT,
CW_USEDEFAULT,
CW_USEDEFAULT,
CW_USEDEFAULT,
NULL,
NULL,
NULL,
NULL)) == NULL)
{
printf("CreateWindow() failed with error %d\n", GetLastError());
return NULL;
}
return Window;
}