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Winsock 2 I/O Methods 5 Part 7
What do we have in this chapter 5 part 7?
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The Overlapped Example Using AcceptEx()
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Running the Server and Client Program
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The Overlapped Example Using AcceptEx()
The following program example demonstrates the use of AcceptEx() for overlapped model. Create a new empty Win32 console mode application and add the project/solution name.
Add the following source code. |
// Description:
//
// This sample illustrates how to develop a simple echo server Winsock
// application using the Overlapped I/O model with event notification. This
// sample is implemented as a console-style 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 echoes (this is why we call it an echo server) the data back in
// it's original form until the client closes the connection.
//
// Note: There are no command line options for this sample.
//
// Link to ws2_32.lib
#include <winsock2.h>
// Link to mswsock.lib
#include <mswsock.h>
#include <windows.h>
#include <stdio.h>
#define PORT 5150
#define DATA_BUFSIZE 8192
typedef struct _SOCKET_INFORMATION {
CHAR Buffer[DATA_BUFSIZE];
WSABUF DataBuf;
SOCKET Socket;
WSAOVERLAPPED Overlapped;
DWORD BytesSEND;
DWORD BytesRECV;
} SOCKET_INFORMATION, * LPSOCKET_INFORMATION;
int main(int argc, char** argv)
{
DWORD EventTotal = 0;
WSAEVENT EventArray[WSA_MAXIMUM_WAIT_EVENTS];
LPSOCKET_INFORMATION SocketArray[WSA_MAXIMUM_WAIT_EVENTS];
CHAR AcceptBuffer[2 * (sizeof(SOCKADDR_IN) + 16)];
WSAOVERLAPPED ListenOverlapped;
DWORD Bytes;
DWORD Index;
DWORD Flags;
DWORD BytesTransferred;
LPSOCKET_INFORMATION SI;
WSADATA wsaData;
SOCKET ListenSocket, AcceptSocket;
SOCKADDR_IN InternetAddr;
DWORD RecvBytes, SendBytes;
DWORD i;
if ((WSAStartup((2,2),&wsaData)) != 0)
{
printf("WSAStartup() failed with error %d\n", WSAGetLastError());
WSACleanup();
return 1;
}
else
printf("WSAStartup() is OK!\n");
if ((ListenSocket = WSASocket(AF_INET, SOCK_STREAM, 0, NULL, 0, WSA_FLAG_OVERLAPPED)) == INVALID_SOCKET)
{
printf("Failed to get a socket %d\n", WSAGetLastError());
return 1;
}
else
printf("WSASocket() is OK!\n");
InternetAddr.sin_family = AF_INET;
InternetAddr.sin_addr.s_addr = htonl(INADDR_ANY);
InternetAddr.sin_port = htons(PORT);
if (bind(ListenSocket, (PSOCKADDR) &InternetAddr, sizeof(InternetAddr)) == SOCKET_ERROR)
{
printf("bind() failed with error %d\n", WSAGetLastError());
return 1;
}
else
printf("bind() is OK!\n");
if (listen(ListenSocket, 5))
{
printf("listen() failed with error %d\n", WSAGetLastError());
return 1;
}
else
printf("listen() is OK! I am listening...\n");
// Setup the listening socket for connections
if ((AcceptSocket = WSASocket(AF_INET, SOCK_STREAM, 0, NULL, 0, WSA_FLAG_OVERLAPPED)) == INVALID_SOCKET)
{
printf("Failed to get a socket %d\n", WSAGetLastError());
return 1;
}
else
printf("WSASocket() is OK!\n");
ZeroMemory(&ListenOverlapped, sizeof(OVERLAPPED));
if ((EventArray[0] = ListenOverlapped.hEvent = WSACreateEvent()) == WSA_INVALID_EVENT)
{
printf("WSACreateEvent() failed with error %d\n", WSAGetLastError());
return 1;
}
else
printf("WSACreateEvent() is OK!\n");
EventTotal = 1;
if (AcceptEx(ListenSocket, AcceptSocket, (PVOID) AcceptBuffer, 0,
sizeof(SOCKADDR_IN) + 16, sizeof(SOCKADDR_IN) + 16, &Bytes, &ListenOverlapped) == FALSE)
if (WSAGetLastError() != ERROR_IO_PENDING)
{
printf("AcceptEx() failed with error %d\n", WSAGetLastError());
return 1;
}
else
printf("AcceptEx() is OK!\n");
// Process asynchronous AcceptEx, WSASend, WSARecv requests
while(TRUE)
{
if ((Index = WSAWaitForMultipleEvents(EventTotal, EventArray, FALSE, WSA_INFINITE, FALSE)) == WSA_WAIT_FAILED)
{
printf("WSAWaitForMultipleEvents() failed %d\n", WSAGetLastError());
return 1;
}
else
printf("WSAWaitForMultipleEvents() is OK!\n");
// If the event triggered was zero then a connection attempt was made
// on our listening socket
if ((Index - WSA_WAIT_EVENT_0) == 0)
{
// Check the returns from the overlapped I/O operation on the listening socket
if (WSAGetOverlappedResult(ListenSocket, &(ListenOverlapped), &BytesTransferred, FALSE, &Flags) == FALSE)
{
printf("WSAGetOverlappedResult() failed with error %d\n", WSAGetLastError());
return 1;
}
else
printf("WSAGetOverlappedResult() is OK!\n");
printf("Socket %d got connected...\n", AcceptSocket);
if (EventTotal > WSA_MAXIMUM_WAIT_EVENTS)
{
printf("Too many connections - closing socket.\n");
closesocket(AcceptSocket);
continue;
}
else
{
// Create a socket information structure to associate with the accepted socket
if ((SocketArray[EventTotal] = (LPSOCKET_INFORMATION) GlobalAlloc(GPTR,
sizeof(SOCKET_INFORMATION))) == NULL)
{
printf("GlobalAlloc() failed with error %d\n", GetLastError());
return 1;
}
else
printf("GlobalAlloc() for LPSOCKET_INFORMATION is OK!\n");
// Fill in the details of our accepted socket
SocketArray[EventTotal]->Socket = AcceptSocket;
ZeroMemory(&(SocketArray[EventTotal]->Overlapped), sizeof(OVERLAPPED));
SocketArray[EventTotal]->BytesSEND = 0;
SocketArray[EventTotal]->BytesRECV = 0;
SocketArray[EventTotal]->DataBuf.len = DATA_BUFSIZE;
SocketArray[EventTotal]->DataBuf.buf = SocketArray[EventTotal]->Buffer;
if ((SocketArray[EventTotal]->Overlapped.hEvent = EventArray[EventTotal] = WSACreateEvent())
== WSA_INVALID_EVENT)
{
printf("WSACreateEvent() failed with error %d\n", WSAGetLastError());
return 1;
}
else
printf("WSACreateEvent() is OK!\n");
// Post a WSARecv request to to begin receiving data on the socket
if (WSARecv(SocketArray[EventTotal]->Socket, &(SocketArray[EventTotal]->DataBuf), 1, &RecvBytes, &Flags,
&(SocketArray[EventTotal]->Overlapped), NULL) == SOCKET_ERROR)
{
if (WSAGetLastError() != ERROR_IO_PENDING)
{
printf("WSARecv() failed with error %d\n", WSAGetLastError());
return 1;
}
}
else
printf("WSARecv() is OK!\n");
EventTotal++;
}
// Make a new socket for accepting future connections and post another AcceptEx call
if ((AcceptSocket = WSASocket(AF_INET, SOCK_STREAM, 0, NULL, 0,
WSA_FLAG_OVERLAPPED)) == INVALID_SOCKET)
{
printf("Failed to get a socket %d\n", WSAGetLastError());
return 1;
}
else
printf("WSASocket() is OK!\n");
WSAResetEvent(EventArray[0]);
ZeroMemory(&ListenOverlapped, sizeof(OVERLAPPED));
ListenOverlapped.hEvent = EventArray[0];
if (AcceptEx(ListenSocket, AcceptSocket, (PVOID) AcceptBuffer, 0,
sizeof(SOCKADDR_IN) + 16, sizeof(SOCKADDR_IN) + 16, &Bytes, &ListenOverlapped) == FALSE)
{
if (WSAGetLastError() != ERROR_IO_PENDING)
{
printf("AcceptEx() failed with error %d\n", WSAGetLastError());
return 1;
}
}
else
printf("AcceptEx() is OK!\n");
continue;
}
SI = SocketArray[Index - WSA_WAIT_EVENT_0];
WSAResetEvent(EventArray[Index - WSA_WAIT_EVENT_0]);
if (WSAGetOverlappedResult(SI->Socket, &(SI->Overlapped), &BytesTransferred, FALSE, &Flags) == FALSE)
{
printf("WSAGetOverlappedResult() failed with error %d\n", WSAGetLastError());
return 1;
}
else
printf("WSAGetOverlappedResult() is OK!\n");
// First check to see if the peer has closed the connection and if so
// then close the socket and cleanup the SOCKET_INFORMATION structure
// associated with the socket
if (BytesTransferred == 0)
{
printf("Closing socket %d\n", SI->Socket);
if (closesocket(SI->Socket) == SOCKET_ERROR)
{
printf("closesocket() failed with error %d\n", WSAGetLastError());
}
else
printf("closesocket() is OK!\n");
GlobalFree(SI);
WSACloseEvent(EventArray[Index - WSA_WAIT_EVENT_0]);
// Cleanup SocketArray and EventArray by removing the socket event handle
// and socket information structure if they are not at the end of the arrays
if ((Index - WSA_WAIT_EVENT_0) + 1 != EventTotal)
for (i = Index - WSA_WAIT_EVENT_0; i < EventTotal; i++)
{
EventArray[i] = EventArray[i + 1];
SocketArray[i] = SocketArray[i + 1];
}
EventTotal--;
continue;
}
// Check to see if the BytesRECV field equals zero. If this is so, then
// this means a WSARecv call just completed so update the BytesRECV field
// with the BytesTransferred value from the completed WSARecv() call
if (SI->BytesRECV == 0)
{
SI->BytesRECV = BytesTransferred;
SI->BytesSEND = 0;
}
else
{
SI->BytesSEND += BytesTransferred;
}
if (SI->BytesRECV > SI->BytesSEND)
{
// Post another WSASend() request
// Since WSASend() is not guaranteed to send all of the bytes requested,
// continue posting WSASend() calls until all received bytes are sent
ZeroMemory(&(SI->Overlapped), sizeof(WSAOVERLAPPED));
SI->Overlapped.hEvent = EventArray[Index - WSA_WAIT_EVENT_0];
SI->DataBuf.buf = SI->Buffer + SI->BytesSEND;
SI->DataBuf.len = SI->BytesRECV - SI->BytesSEND;
if (WSASend(SI->Socket, &(SI->DataBuf), 1, &SendBytes, 0, &(SI->Overlapped), NULL) == SOCKET_ERROR)
{
if (WSAGetLastError() != ERROR_IO_PENDING)
{
printf("WSASend() failed with error %d\n", WSAGetLastError());
return 1;
}
}
else
printf("WSASend() is OK!\n");
}
else
{
SI->BytesRECV = 0;
// Now that there are no more bytes to send post another WSARecv() request
Flags = 0;
ZeroMemory(&(SI->Overlapped), sizeof(WSAOVERLAPPED));
SI->Overlapped.hEvent = EventArray[Index - WSA_WAIT_EVENT_0];
SI->DataBuf.len = DATA_BUFSIZE;
SI->DataBuf.buf = SI->Buffer;
if (WSARecv(SI->Socket, &(SI->DataBuf), 1, &RecvBytes, &Flags, &(SI->Overlapped), NULL) == SOCKET_ERROR)
{
if (WSAGetLastError() != ERROR_IO_PENDING)
{
printf("WSARecv() failed with error %d\n", WSAGetLastError());
return 1;
}
}
else
printf("WSARecv() is OK!\n");
}
}
}
Build and run the project.
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Running the Server and Client Programs
Firstly we run the server program. The following screenshot shows a sample output.
Then we run the client program.
The following screenshot shows a sample server output when some connection were completed.
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