[Tfug] Innocuous/ubiquitous service(s)?

[Bexley Hall]

Hi,

I need to pick an IP service that is:
- (relatively) commonplace (even if not ubiquitous)
   (i.e., doesn't "stand out" due to its "scarcity")
- easy to implement *robustly* (i.e., NO bugs in implementation)
- easily differentiated for each instantiation (i.e., my deployment
   on (IPa,PORTb) appears, out-of-the-box, *different* from your
   deployment on (IPc,PORTd)
- "unsurprising" if run on a "non-standard" port (e.g., running
   HTTPd on port 3422 would raises eyebrows)
- and fairly lightweight.

SMTP and HTTP were the first two that came to mind.  But,
SMTP wants to run on a port that is often blocked.  And, HTTP
is too hard to differentiate ("automatically") from one instance
to another (requires too much involvement from the user/operator).

DNS would be a good candidate as well (except for port number)
though differentiating instances might be a challenge.

NNTP is probably the safest bet but so obsolescent that I
think it might draw attention to itself!

(I wrote this slowly for those you who can't read very fast...)

Thx,
--don