Trying to limit number of bytes transferred to at least 15 bytes before async_read call back I have got callbacks with sizes: 0,1,2,3,4 and 5 (so total indeed 15) But I was expecting only single callback with size 15. How I can fix the issue? Thanks Vlad. linux suse 2.6.16 boost 1.39 gcc 4.1.2 //boost asio stripped part. BufferSize=1000; class test{ vector<char> read_buffer_; boost::asio::ip::tcp::socket socket_; //socket was inited correctly. test() { read_buffer_.reserve(BufferSize); } void handle_connect( const boost::system::error_code& err, boost::asio::ip::tcp::resolver::iterator endpoint_iterator ) { if (!err) { boost::asio::async_read(socket_,boost::asio::buffer(read_buffer_, BufferSize), //requested at least 15 bytes!! boost::asio::transfer_at_least(15), boost::bind(&test::handle_read, this, boost::asio::placeholders::error)); } else { cerr<<err.message()<<endl; } } void handle_read( const boost::system::error_code& err) { if (!err) { //+++++++++++++++++++++++++++ //expecting to get at least 15! //But have not get those. //+++++++++++++++++++++++++++ cerr<<"Got:"<<read_buffer_.size()<<endl; boost::asio::async_read(socket_,boost::asio::buffer(read_buffer_, MaxResponce), //requested at least 15 bytes!! boost::asio::transfer_at_least(15), boost::bind(&test::handle_read, this, boost::asio::placeholders::error) ); } else { cerr<<err.message()<<endl; } } }; =============================================================================== Please access the attached hyperlink for an important electronic communications disclaimer: http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html ===============================================================================