boost::asio read response

Question

I am trying to connect to an IRC server (twitch.tv). The connection is successful but I don't know how to read the response from the server properly. More specifically I have trouble in this line: boost::asio::read(s, boost::asio::buffer(reply, MAX_LENGTH)); .

If I use MAX_LENGTH (1024), which is a number larger than the size of the response message then the program doesn't seem to terminate. If I use a number like 64, I can read only 64 characters of the message. Can I somehow read until \\r\\n or something ? How can I do this properly ?

#include <boost/asio.hpp>
#include <iostream>

using namespace std;

int main(int argc, char *argv[])
{
    try
    {
        char         HOSTNAME[] = "irc.chat.twitch.tv";
        char         PORT[]     = "6667";
        char         PASS[]     = "PASS oauth:123\r\n";
        char         NICK[]     = "NICK 123\r\n";
        char         USER[]     = "USER 123\r\n";
        const size_t MAX_LENGTH = 1024;

        boost::asio::io_service        io_service;
        boost::asio::ip::tcp::socket   s(io_service);
        boost::asio::ip::tcp::resolver resolver(io_service);
        boost::asio::connect(s, resolver.resolve({HOSTNAME, PORT}));
        cout << "connected\n";

        boost::asio::write(s, boost::asio::buffer(PASS, strlen(PASS)));
        boost::asio::write(s, boost::asio::buffer(NICK, strlen(NICK)));
        boost::asio::write(s, boost::asio::buffer(USER, strlen(USER)));
        cout << "sent 3 messages\n";

        char   reply[MAX_LENGTH];

        size_t reply_length     = boost::asio::read(s, 
            boost::asio::buffer(reply, MAX_LENGTH));
        // execution never reaches here 
        std::cout << "Reply is: ";
        std::cout.write(reply, reply_length);
        std::cout << "\n";
    }
    catch (std::exception &e)
    {
        std::cerr << "Exception: " << e.what() << "\n";
    }

    return 0;
}

Answer 1

I am not familiar with IRC protocol but from a quick look at the RFC it looks like it is text based. In that case I would suggest using boost::asio::read_until for the response.

If you decide that this fits your problem, please keep in mind that read_until internally might read bytes from the incoming stream beyond the specified delimiter. So pay close attention when extracting data from the provided streambuf (you need to use the value returned from read_until).

Have a look at the documentation: http://www.boost.org/doc/libs/1_61_0/doc/html/boost_asio/reference/read_until/overload3.html

Answer 2

Read tries to read until the buffer is full before returning. If you want the function to return after having read anything at all use read_some .

s.read_some(boost::asio::buffer(reply, MAX_LENGTH));