Thanks @Guillaume Rongier !  That works great.  FYI ... we can see the request attempt on the IRIS side with a Description = "%Service_SuperServer login failure", noting the IP Address of your Linux web server, and Event Data which mentions "Error message: ERROR #949: Unable to get full header of message within timeout" 

^SSADMIN is a TrakCare utility so you will need to look in the TrakCare documentation on that (and/or add the TrakCare tag to this question - not sure if that will send out new notifications to people who follow that Tag).  The Production page from the SMP is for the InterSystems IRIS Interoperability Productions for which I linked docs above.  I am guessing the "Interfacing" is a specific TrakCare feature which uses Productions and other pieces of InterSystems IRIS Interoperability beneath the covers. 

Very nice initial How-To!  Thank you especially for the animated GIFs!

@Phillip Wu - you will need to be a little more specific.  There are a number of 'Gateways' in InterSystems products (e.g. Web Gateway, SQL Gateway, etc), but I don't know of any of them that are specifically an interoperability component.  You could have an interface which uses a gateway to get data, but again the specifics are really important here :)   Also, if you are using a production that someone else created, they could call something a "Gateway" which is their term and not necessarily indicative of something specific to an InterSystems product.

Great write-up (thank you for the animated GIFs!)  This makes it so simple for people to get started - appreciate the write-up