Accepting FIX Session Without a Prior Creation of Session Object

Sometimes there is a requirement to accept an incoming FIX session 'on the fly', without the prior creation of the OnixS::FIX::Session object. This often happens when an unknown session-initiator is trying to connect to the Engine. For this reason, OnixS C++ FIX Engine exposes an ability to accept such a connection by creating a temporary session-acceptor and to respond to the counterparty. To take advantage of this feature it is necessary to inherit from the OnixS::FIX::IEngineListener class, to overwrite the OnixS::FIX::IEngineListener::onUnknownIncomingConnection method and register isntance of inherited listener with the OnixS::FIX::Engine instance using the OnixS::FIX::Engine::registerListener method.

An automatically created OnixS::FIX::Session object that corresponds to the incoming FIX connection is available as a parameter in overridden OnixS::FIX::IEngineListener::onUnknownIncomingConnection member.

To accept the incoming connection, update value of acceptConnection parameter to be true. Otherwise the incoming connection will be rejected and the created OnixS::FIX::Session object will be disposed of by the Engine.

Example

#include <OnixS/FIXEngine.h>

using namespace OnixS::FIX;

class UnknownSessionAcceptor 
    : public IEngineListener, public ISessionListener
{
public:
    UnknownSessionAcceptor(
        bool acceptConnection, const string& rejectReason)
        : acceptConnection_(acceptConnection), 
          rejectReason_(rejectReason), 
          session_(NULL)
    {
    }

        virtual ~UnknownSessionAcceptor()
        {
                delete session_;
        }               

        virtual void onUnknownIncomingConnection(
        const Message& incomingLogon, Session* session, 
        bool* acceptConnection, std::string* rejectReason)
        {                       
                *acceptConnection = acceptConnection_;

                if(acceptConnection_)
                {
                        session_ = session;

            // Session is already created, but we would like somehow listen to 
            // session events. Following statement exactly does what do we want.
                        session_->registerListener(this); 
                }
                else
                {
            // Once session will be rejected, Engine will send logout message.
            // Engine will use reject reason as text in logout message.
                        *rejectReason = rejectReason_; 
                }
        }

        virtual void onInboundApplicationMsg(const Message& message, Session*)
        {
                // Process incoming messages in same way as working with usual sessions.
        }                               

private:
        bool acceptConnection_;         
        
    std::string rejectReason_;

        OnixS::FIX::Session* session_;
};

// ...

UnknownSessionAcceptor unknownSessionAcceptor(true, "");

Engine::instance()->registerListener(&unknownSessionAcceptor);

// ...