TCP Winsock: accept multiple connections/clients - c++

Question

I tried to can multiply clients, and send it to each one.
But it working only for one, after one client connected the server just useless for incoming connections.
while(true)
{
if(Sub = accept(Socket, (sockaddr*)&IncomingAddress, &AddressLen))
{
for(int i = 0; i < MaxUsers; i++)
{
if(!ClientAddress[i].sin_family)
{
ClientAddress[i] = IncomingAddress;
char Version[128], Dir[256], Path[256], URL[128], Message[256];
GetCurrentDirectory(256, Dir);
sprintf(Path, "%s\\Version.ini", Dir);
GetPrivateProfileString("Default", "Version", "1.0.0.0", Version, 128, Path);
GetPrivateProfileString("Default", "URL", "", URL, 128, Path);
GetPrivateProfileString("Default", "Message", "", Message, 256, Path);
send(Sub, Version, 128, 0);
send(Sub, Message, 256, 0);
break;
}
}
continue;
}
}

Answer 1

Of course new clients cannot be accepted because the server handles just accepted client, i.e. the server is busy.
The solution is simple: create a new thread for each accepted client and handle the client session there. Just use _beginthreadex() (#include <process.h>):
unsigned __stdcall ClientSession(void *data)
{
SOCKET client_socket = (SOCKET)data;
// Process the client.
}
int _tmain(int argc, _TCHAR* argv[])
{
...
SOCKET client_socket;
while ((client_socket = accept(server_socket, NULL, NULL))) {
// Create a new thread for the accepted client (also pass the accepted client socket).
unsigned threadID;
HANDLE hThread = (HANDLE)_beginthreadex(NULL, 0, &ClientSession, (void*)client_socket, 0, &threadID);
}
}
By the way, send()/recv() functions do not guarantee that all the data would be sent/received at one call. Please see the documentation for return value of these functions.

Answer 2

After accepting socket create separate thread for client requests. Then continue wait for new accepting.
For example:
...
while (1)
{
AcceptSocket = SOCKET_ERROR;
while (AcceptSocket == SOCKET_ERROR )
{
AcceptSocket = accept( m_socket, NULL, NULL );
}
printf( "Client Connected.\n");
DWORD dwThreadId;
CreateThread (NULL, 0, ProcessClient, (LPVOID) AcceptSocket, 0, &dwThreadId);
}
...
Where ProcessClient function could be like this:
DWORD WINAPI ProcessClient (LPVOID lpParameter)
{
SOCKET AcceptSocket = (SOCKET) lpParameter;
// Send and receive data.
int bytesSent;
int bytesRecv = SOCKET_ERROR;
char sendbuf[2000]="";
char recvbuf[2000]="";
char timebuf[128];
sprintf(sendbuf, "Hello, it's a test server at %s:%d (commands: 1, 2, exit)\n", ipaddr, port);
bytesSent = send( AcceptSocket, sendbuf, strlen(sendbuf), 0);
if (bytesSent == SOCKET_ERROR)
{
printf( "Error at send hello: %ld\n", WSAGetLastError());
goto fin;
}
while (1)
{
_strtime( timebuf );
ZeroMemory (recvbuf, sizeof(recvbuf));
bytesRecv = recv( AcceptSocket, recvbuf, 32, 0);
printf( "%s Client said: %s\n", timebuf, recvbuf);
if (strcmp(recvbuf, "1") == 0)
{
sprintf(sendbuf, "You typed ONE\n");
//printf("Sent '%s'\n", sendbuf);
bytesSent = send( AcceptSocket, sendbuf, strlen(sendbuf), 0);
if (bytesSent == SOCKET_ERROR)
{
printf( "Error at send: %ld\n", WSAGetLastError());
goto fin;
}
}
else if (strcmp(recvbuf, "2") == 0)
{
sprintf(sendbuf, "You typed TWO\n");
//printf("Sent '%s'\n", sendbuf);
bytesSent = send( AcceptSocket, sendbuf, strlen(sendbuf), 0);
if (bytesSent == SOCKET_ERROR)
{
printf( "Error at send: %ld\n", WSAGetLastError());
goto fin;
}
}
else if (strcmp(recvbuf, "exit") == 0)
{
printf( "Client has logged out\n", WSAGetLastError());
goto fin;
}
else
{
sprintf(sendbuf, "unknown command\n");
//printf("Sent '%s'\n", sendbuf);
bytesSent = send( AcceptSocket, sendbuf, strlen(sendbuf), 0);
if (bytesSent == SOCKET_ERROR)
{
printf( "Error at send: %ld\n", WSAGetLastError());
goto fin;
}
}
}
fin:
printf("Client processed\n");
closesocket(AcceptSocket);
return 0;
}