Winsock Local Feedback Delay

Question

I use tcp sockets to provide interprocess communication between two applications in Windows XP. I chose tcp sockets for various reasons. I see an average round-trip time of 2.8 ms. This is much slower than I expected. Profiling seems to show that a delay occurs between one application calling send and returning the other end.

I also have applications, a daemon and a client. They are structured like this pseudocode:

Daemon thread 1 (Listens for new connections):

while (1) {
   SOCKET listener_socket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
   bind(listener_socket, (SOCKADDR*)&server_info, sizeof(SOCKADDR));
   listen(listener_socket, 1);
   SOCKET client_socket = accept(listener_socket, NULL, NULL);
   closesocket(listener_socket);
   CreateThread(client_thread);
 }

thread Demon client_socket (listens for packets from the client):

char cmdBuf[256];
int cmdBufAmountData = 0;

while (1)
{   
    char recvBuf[128];
    int bytesTransferred = recv(m_clientSocket, recvBuf, sizeof(recvBuf), 0);

    // Copy received data into our accumulated command buffer (commands 
    // may be split across packet boundaries)
    memcpy(cmdBuf + cmdBufAmountData, recvBuf, bytesTransferred);
    cmdBufAmountData += bytesTransferred;

    // See if there is one or more complete commands in cmdBuf 
    // (commands are separated by '\0')
    while (commandExists(cmdBuf, cmdBufAmountData))
    {
        // do stuff with command
        send(m_clientSocket, outBuf, msgLen, 0);

        // Throw away the command we just processed by shuffling 
        // the contents of the command buffer left
        for (int i = 0; i < cmdBufAmountData - cmdLen; i++)
            cmdBuf[i] = cmdBuf[i + cmdLen];
        cmdBufAmountData -= cmdLen;
    }
}

Client Stream 1:

start_timer();
send(foo);
recv(barBuf);
end_timer();       // Timer shows values from 0.7ms to 17ms. Average 2.8ms.

Any ideas why latency is so bad? I suspected a Nagel algorithm, but stuffed my code:

BOOL bOptVal = TRUE;
setsockopt(socket, IPPROTO_TCP, TCP_NODELAY, (char*)&bOptVal, sizeof(BOOL));

Does not help. Do I need to do this on both client and daemons (I do)?

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Answer 1

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SOCKET listener_socket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
bind(listener_socket, (SOCKADDR*)&server_info, sizeof(SOCKADDR));
listen(listener_socket, 1);
while (1) {
   SOCKET client_socket = accept(listener_socket, NULL, NULL);
   closesocket(listener_socket);
   CreateThread(client_thread);
 }

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Answer 2

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