Re: Scalable tcp server

Ignoring the issue of trying to send structs over a socket & the
Sleep() call, shouldn't your loop be something along the lines of the
following to handle a possible incomplete read of HEADER on your call
to Recv()?

// Peek for data
int nReadSoFar = 0 ;
while(1) {
if ((ret = m_Socket.Recv(
((char *) &H) + nReadSoFar
,sizeof(H)-nReadSoFar
,MSG_PEEK)) == SOCKET_ERROR)
return false;

// See if client is disconnected
if (ret == 0) return false;

nReadSoFar += ret ;
if(nReadSoFar >= (int) sizeof(NH)) {
break ;
}
Sleep(5);
}


On Jul 13, 8:55 am, h...@xxxxxxxxxxxxxxx wrote:
Thanks to everyone who has answered this so far.

As per suggestions I did some profiling and with a few small patches I
managed to boost the speed quite a bit. These patches were some
useless wait's here and there and some improvements with a little bit
of caching.

However now with those patches done I hit a new problem. Once in a
while I get errors on the client side and things just stop working.
This problem is *only* happening when I perform stress tests with
multiple socket connections.

I have identified it to be this piece of code on the client:

bool Csocket::SafeRecv()
{
int nIndex = 0;
int nLeft;
int ret;
HEADER H;

// Peek for data
do
{
if ((ret = m_Socket.Recv(&H, sizeof(H), MSG_PEEK)) ==
SOCKET_ERROR)
return false;

// See if client is disconnected
if (ret == 0) return false;

Sleep(5);
} while (ret < (int) sizeof(NH));

// The header has been received and tells you how much data is left
to receive.
nLeft = ENDIAN(H.lLength);

ResizeMemory(nLeft);

// Get the rest
while (nLeft > 0)
{
ret = m_Socket.Recv(&m_pBuffer[nIndex], nLeft, 0);
// Either the client disconnected or a socket error occured.
if (ret == SOCKET_ERROR) return false;
if (ret == 0) return false;

nLeft -= ret;
nIndex += ret;
}

return true;

}

I should make it clear that SOCKET_ERROR is defined as -1 and that
m_Socket.Recv() is just a wrapper around recv().

In the above code I read the header before reading rest of the data.
This is required in order to read how much more data is missing and
perform some cryptography services which I left out.

I have identified that something weird is going on with msg_peek since
"if (ret == 0) return false;" sometimes gets invoked. This means that
the server should have dropped the client connection but this is not
the case. I know that the server didn't do that just for the fun of
it.

Can anyone propose a better/ more safe way of achiving the same as
above?
What I want is to read the network header as 1 recv() before reading
rest of the data. This means that I'd like to wait on the client side
until I know that there is enough data to be read.

Thanks.

-- Henrik

.

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