Question

I’m using QuickFIX and C# to create a FIX acceptor (server). I want the client (the FIX initiator) to logon using a username and password. However, I’m not sure how I can do that in QuickFIX.

By debugging into the QuickFIX source code I have discovered the following sequence of events:

• QuickFIX will call Session::verify to verify the logon.
• Session::verify will perform various checks of things like comp ID’s and sequence numbers and at some point determine that the logon received is valid.
• Session::verify will then call the Application::fromAdmin callback which I assume is the natural place to customize things like logon.
• However, at this point the logon has already been determined to be OK by QuickFIX and a corresponding logon message will be returned by the acceptor when the callback returns.

How do I customize the FIX logon process in an acceptor? Is modifying the QuickFIX code my only option?

Answer 1

If you are using FIX 4.3 or later, the Logon message can have a Password tag. If you are using a previous version, make it a custom tag and add it to the dictionaries.

In the fromAdmin handler, check that the password is correct (from a lookup table or elsewhere). If it is not, throw a RejectLogon exception. If this exception isn’t thrown, QuickFix will assume everything is a-ok and log the user on.

Example (needs more sanity checks):

public void fromAdmin(Message message, SessionID id)
{
   var logon = message as QuickFix44.Logon;

   if (logon != null)
   {
      string userName = logon.getUserName().getValue();
      string expectedPassword = PasswordsByUser[userName];

      string suppliedPassword = logon.getPassword().getValue();

      if(expectedPassword != suppliedPassword)
          throw new RejectLogon();
   }     
}