HTTPS/1.1 200 OK
Content-Type: application/json; charset=utf-8
Content-Length: 48
Connection: Close
{
 "DATA": {
 "ERROR": "ANY USER IS LOGIN"
 }
}do {
            char buf[1024] = "\0";
            size_t bytes_transferred = sock.read_some(boost::asio::buffer(buf), ec);
            if (!ec) response.append(buf, buf + bytes_transferred);
        } while (!ec);  
  
  #include <iostream>
#include <algorithm>
#include <iterator>
using namespace std;
int main()
{
    char buf[1500]{"HTTPS/1.1 200 OK\nContent-Type: \
                    application/json; charset=utf-8\n\
                    Content-Length: 48\
                    Connection: Close{\"DATA\": {\"ERROR\":\
                     \"ANY USER IS LOGIN\"}}"};
    auto bs{ find(begin(buf) , end(buf)  , '{' ) };
    auto es{ find(rbegin(buf), rend(buf) , '}' ) };
    copy(bs, es.base(), ostream_iterator<char>(cout));
}{"DATA": {"ERROR": "ANY USER IS LOGIN"}}