boost asio socket async read methods block until a newline is received

Question

I am (in effect) writing a telnet-like app. (It's far more complicated than that.) I need to receive inbound IP connections and transfer data. I'm using boost::asio to do the socket work.

Everything is fine, except I haven't been able to convince asio to call my handler the moment data is available. To test, I telnet to my host/port (that is working), type something, and hit newline. My debug output appears. That's great.

If I don't hit newline, my app is quiet. I might as well just be calling "readline".

I have tried a variety of things. I tried doing async_read_until, passing a method that returns a pair when there is any data. It doesn't get called until a newline.

I tried using async_read with a 1-byte buffer. It gets called n times as appropriate, but only once I hit newline on the terminal.

And for that matter, telnet is echoing the characters as I type, which also seems like a hint.

Here's the code for using async_read_until:

boost::asio::async_read_until(socket, receiveBuffer, haveData,
        boost::bind(&TCPConnection::dataReceived,
              shared_from_this(),
              boost::asio::placeholders::error));

std::pair<TCPConnection::Iterator, bool>
haveData(TCPConnection::Iterator begin, TCPConnection::Iterator end)
{
    if (begin != end) {
        return std::make_pair(end, true);
    }
    // no data.
    return std::make_pair(begin, false);
}

Here's the code for using a 1-byte buffer:

char * buffer = new char(1);

auto hPtr = boost::bind(&TCPConnection::handler,
        shared_from_this(), boost::asio::placeholders::error,
        boost::asio::placeholders::bytes_transferred);
boost::asio::async_read(socket, boost::asio::buffer(buffer, 1), hPtr);

My socket definition:

boost::asio::ip::tcp::socket socket(io_service);

I presume (somehow) I need to get the socket into a different mode than it's in. I don't have a clue how.

In more fairness, I hate the 1-byte-buffer thing. I'd rather give it a proper size buffer but have it wait until there's any data, but then just give me what it's got. But if I have to read them 1 byte at a time, I can live with that.

Answer 1

Okay, consider this answered. It wasn't my program. It was telnet, which by default is in line mode. See Daniel's question and my responses in the comments to the original post.