Thread: How does select work when recv-ing?

I am trying to learn socket programming but I am having trouble with partial recv-ing.

I want to get all the text in yahoo.com/index.html.

Code:

    TCPClient client("www.yahoo.com",80);

    client.setTimeOut(1,0);

    client.write("GET http://www.yahoo.com/index.html HTTP/1.1\nHost: www.yahoo.com\n\n");

    cout << client.read();

I only get 512 bytes at a time using my recv function so that is why I loop it.

During the first few loops the select function returns 1 and the recv function returns 512. After all the text has been downloaded from yahoo the select function keeps returning 1 and the recv function returns 0. Therefore it gets stuck in an infinite while loop.

I thought the select function returned 0 when the recv function didn't have any data to return and would also return 0. Should I just set the while loop to stop when size equals 0 or I am using these functions wrong? I meant for the while loop to stop when there was no more data to receive from the the socket, which is what I though select told me. How should I do this correctly?

Code:

std::string TCPClient::read()
{
    std::string buffer;
    char b[512];
    int size = 0;

    FD_ZERO(&mReadFds);
    FD_SET(mSocket, &mReadFds);

    int error = select(mSocket + 1, &mReadFds, 0, 0, &mTimeOut);

    while (error > 0)
    {
        if(FD_ISSET(mSocket, &mReadFds))
        {
            size = recv(mSocket, b, 512, 0);
            if (size == SOCKET_ERROR)
            {
                mState = CS_BROKEN;
                return buffer;
            }

            b[size] = 0;
            buffer += b;
        }

        FD_ZERO(&mReadFds);
        FD_SET(mSocket, &mReadFds);

        error = select(mSocket + 1, &mReadFds, 0, 0, &mTimeOut);

        std::cout << "error: " << error << std::endl;
        std::cout << "size:  " << size << std::endl;

    }

    if (error == SOCKET_ERROR)
    {
        mState = CS_BROKEN;
        return buffer;
    }

    mState = CS_CONNECTED;
    return buffer;
}

Thanks for any help.

Because a recv() returning 0 is special perhaps?
Maybe read the manual to find out why.