Connection refused to mysql database from C++ driver - c++

Question

Problem
I'm following tutorial on Connect/C++ provided by dev.mysql. After copying the example and successfully compiling and linking it, I run into following issue:
terminate called after throwing an instance of 'sql::SQLException'
what(): Can't connect to MySQL server on '127.0.0.1' (111)
From what I know 111 stands for Permission Denied.
Setup
Here is the example code taken from here and slightly modified:
#include <mysql_driver.h>
int main()
{
auto driver = sql::mysql::get_mysql_driver_instance();
auto con = driver->connect("tcp://127.0.0.1:0", "root", "123");
delete con;
}
Trying with tcp://127.0.0.1:3306 give the same result.
Here is the CMakeLists.txt:
cmake_minimum_required(VERSION 3.9)
project(mysql_try)
set(CMAKE_CXX_STANDARD 14)
set(SOURCE_FILES main.cpp)
add_executable(mysql_try ${SOURCE_FILES})
target_include_directories(mysql_try PUBLIC /usr/local/include/mysql++)
target_link_libraries(mysql_try mysqlclient /usr/local/lib/libmysqlcppconn-static.a pthread dl)
I can easily run mysql with the credentials in the code. I disabled networking, so that it would only listen on localhost. Running
mysql> SHOW GLOBAL VARIABLES LIKE 'PORT';
gave me 0, so I guess it is port 0.
C Connector and command line interfaces work just fine.
My OS is ubuntu 16.04.

Answer 1

I disabled networking, so that it would only listen on localhost.
There's a difference between disabling networking all together (tcp) and specifying tcp to listen ONLY on your loopback adapter (127.0.0.1). Your mysql client is almost certainly connecting via Unix Socket, not TCP, which is why that works fine. Verify that by running mysql --protocol tcp. If that fails, then you know you disabled TCP connections all together, and it's connecting via Unix Socket.
connect("tcp://127.0.0.1:0"
If you did disable networking with skip-networking you need to change your connect() to reference your socket file instead. See the docs
unix://path_name
This URL format enables use of Unix domain socket files for connections to the local host on Unix and Unix-like systems. The path_name value is the socket file path name, just as for the --socket option of MySQL clients such as mysql and mysqladmin running on Unix (see Connecting to the MySQL Server).
Find your socket with:
mysql> SHOW GLOBAL VARIABLES LIKE 'socket'
If you want to keep your connect string the same, remove skip-networking and instead add
bind-address = 127.0.0.1
That should fix it!