OnixS C++ FIX Engine  4.4.0
API Documentation
Logon Password Authentication

While Accepting an incoming FIX connection, additional authentication checks may be required. The typical checks are Logon username/password and source IP address.

The required authentification logic could be added to the OnixS::FIX::ISessionListener::onInboundSessionMsg(..) method. If the authentication fails and the FIX connection needs to be rejected (closed) then the std::runtime_error exception (or the derived one) should be thrown.

For example:

bool doAuthentication(const Message& /*message*/, std::string& /*reason*/)
{
// Perform some authentication.
return true;
}
class SessionListener : public ISessionListener
{
public:
void onInboundSessionMsg(Message& message, Session*) ONIXS_FIXENGINE_OVERRIDE
{
if (message.type() == OnixS::FIX::FIX40::Values::MsgType::Logon)
{
std::string reason;
// Do user authentication here
if (!doAuthentication(message, reason))
{
throw std::runtime_error(reason);
}
}
}
};

If the std::runtime_error exception is thrown and OnixS::FIX::EngineSettings::sendLogoutOnException(..) or OnixS::FIX::Session::sendLogoutOnException(..) is set to true then the Logout FIX message will be sent before closing the FIX connection. Otherwise, the connection will be closed immediately.