Making my function which calls async_read asynchronous Boost::asio - c++

Question

I am building an networking application, and being a newbie to Boost asio and networking as a whole had this doubt which might be trivial. I have this application which reads from a file and calls apis accordingly. I am reading json (example):
test.json
{
"commands":
[
{
"type":"login",
"Username": 0,
"Password": "kk"
}
]
}
My main program looks like this :
int main() {
ba::io_service ios;
tcp::socket s(ios);
s.connect({{},8080});
IO io;
io.start_read(s);
io.interact(s);
ios.run();
}
void start_read(tcp::socket& socket) {
char buffer_[MAX_LEN];
socket.async_receive(boost::asio::null_buffers(),
[&](const boost::system::error_code& ec, std::size_t bytes_read) {
(void)bytes_read;
if (likely(!ec)) {
boost::system::error_code errc;
int br = 0;
do {
br = socket.receive(boost::asio::buffer(buffer_, MAX_LEN), 0, errc);
if (unlikely(errc)) {
if (unlikely(errc != boost::asio::error::would_block)) {
if (errc != boost::asio::error::eof)
std::cerr << "asio async_receive: error " << errc.value() << " ("
<< errc.message() << ")" << std::endl;
interpret_read(socket,nullptr, -1);
//close(as);
return;
}
break; // EAGAIN
}
if (unlikely(br <= 0)) {
std::cerr << "asio async_receive: error, read " << br << " bytes" << std::endl;
interpret_read(socket,nullptr, br);
//close(as);
return;
}
interpret_read(socket,buffer_, br);
} while (br == (int)MAX_LEN);
} else {
if (socket.is_open())
std::cerr << "asio async_receive: error " << ec.value() << " (" << ec.message() << ")"
<< std::endl;
interpret_read(socket,nullptr, -1);
//close(as);
return;
}
start_read(socket);
});
}
void interpret_read(tcp::socket& s,const char* buf, int len) {
if(len<0)
{
std::cout<<"some error occured in reading"<<"\n";
}
const MessageHeaderOutComp *obj = reinterpret_cast<const MessageHeaderOutComp *>(buf);
int tempId = obj->TemplateID;
//std::cout<<tempId<<"\n";
switch(tempId)
{
case 10019: //login
{
//const UserLoginResponse *obj = reinterpret_cast<const UserLoginResponse *>(buf);
std::cout<<"*********[SERVER]: LOGIN ACKNOWLEDGEMENT RECEIVED************* "<<"\n";
break;
}
}
std::cout << "RX: " << len << " bytes\n";
if(this->input_type==2)
interact(s);
}
void interact(tcp::socket& s)
{
if(this->input_type == -1){
std::cout<<"what type of input you want ? option 1 : test.json / option 2 : manually through command line :";
int temp;
std::cin>>temp;
this->input_type = temp;
}
if(this->input_type==1)
{
//std::cout<<"reading from file\n";
std::ifstream input_file("test.json");
Json::Reader reader;
Json::Value input;
reader.parse(input_file, input);
for(auto i: input["commands"])
{
std::string str = i["type"].asString();
if(str=="login")
this->login_request(s,i);
}
std::cout<<"File read completely!! \n Do you want to continue or exit?: ";
}
}
The sending works fine, the message is sent and the server responds in a correct manner, but what I need to understand is why is the control not going to on_send_completed (which prints sent x bytes). Neither it prints the message [SERVER]: LOGIN ACKNOWLEDGEMENT RECEIVED, I know I am missing something basic or am doing something wrong, please correct me.
login_request function:
void login_request(tcp::socket& socket,Json::Value o) {
/*Some buffer being filled*/
async_write(socket, boost::asio::buffer(&info, sizeof(info)), on_send_completed);
}
Thanks in advance!!

Answer 1

From a cursory scan it looks like you redefined buffer_ that was already a class member (of IO, presumably).
It's hidden by the local in start_read, which is both UB (because the lifetime ends before the async read operation completes) and also makes it so the member _buffer isn't used.
I see a LOT of confusing code though. Why are you doing synchronous reads from within completion handlers?
I think you might be looking for the composed-ooperation reads (boost::asio::async_read and boost::asio::async_until)